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Buyers’ guide Multi-slice CT scanners CEP08007 March 2009 Contents 2 Introduction ............................................................................................. 3 Technical considerations......................................................................... 9 Operational considerations.................................................................... 29 Economic considerations ...................................................................... 53 Purchasing ............................................................................................ 62 Market review........................................................................................ 72 Acknowledgements ............................................................................. 113 Glossary.............................................................................................. 114 References.......................................................................................... 127 Appendix 1: Supplier contact details ................................................... 142 Appendix 2: EU procurement procedure ............................................. 143 Appendix 3: Supporting sustainable purchasing.................................. 146 Appendix 4: Preparing a specification ................................................. 149 Appendix 5: Example statement of operational requirements.............. 160 Appendix 6: Site visits ......................................................................... 169 Appendix 7: Evaluation scoring ........................................................... 176 Author and report information.............................................................. 181 CEP08007: March 2009 Introduction 3 Scope and purpose This buyers’ guide is designed to help purchasers to select a multi-slice CT scanner which best meets their needs. It covers technical, operational, and economic considerations, provides guidance on the purchasing process, and presents a review of the multi-slice scanners available on the UK market. The guide does not cover PET/CT. It is aimed at a variety of readers involved in the purchasing and decision-making process, including finance directors and capital equipment boards, business managers, radiologists and physicists. Information on the basic principles of CT scanning is provided for the benefit of those with little direct experience of the technology. Those involved in specifying equipment to be purchased will find the market overview and technical specifications useful. Full comparative specifications are available separately (Table 1). Table 1: Comparative specification reports for multi-slice CT systems Report number Report title CEP08024 CT clinical applications software [84] CEP08025 16 slice CT scanner technical specifications [85] CEP08026 32 to 40 slice CT scanner technical specifications [86] CEP08027 64 slice CT scanner technical specifications [87] CEP08028 128 to 320 slice CT scanner technical specifications [88] CEP08029 Wide bore CT scanner technical specifications [89] Overview of a CT scanner Computed tomography (CT) scanners were first introduced into clinical use in 1972 and are now an indispensable tool within the radiology department. The technology has progressed greatly since that time, and the range of clinical applications continues to grow. CT scanning is a cross-sectional imaging modality, and as such offers a key difference from standard diagnostic X-ray imaging. In the latter, structures overlay each other in the resultant image and may be hard to differentiate from each other. However in a CT scan, which utilises X-rays in a different geometrical and data acquisition arrangement, a cross-sectional image results which allows the differentiation of overlying structures. CEP08007: March 2009 Introduction 4 A CT scanner may be purchased to replace or supplement an older scanner, to meet increased demands on the service, or to take advantage of new developments which enable improved diagnostics, faster throughput or other clinical benefits. CT scanners are, however, expensive both to purchase and to operate, hence it is important to select the scanner which offers greatest value for money. Of equal importance to the hardware, is the clinical applications software. This is available for different clinical tasks, and varies in complexity from the standard twodimensional (2D) reconstructions which are available on the scanner console, to more complex three-dimensional (3D) reconstructions and software packages which are often carried out on an ancillary workstation. With the advent of multi-slice CT (MSCT) and volumetric datasets, the facility to perform 3D reconstruction has become an essential component of the CT system. The range of clinical applications software is extensive, and that of greater complexity is purchased optionally. As with any imaging modality involving the use of X-rays, under The Ionising Radiation (Medical Exposure) Regulations, 2000 (IR(ME)R 2000) [22], the hazards of ionising radiation must be considered and the use of the technology justified, ie it should only be employed if the clinical benefit of the examination outweighs the risk of cancer induction or other radiation-induced morbidity. The price of the additional diagnostic information obtained from a CT scan is the higher radiation dose compared with a conventional X-ray; this is by a factor of the order of 10 for head and body routine imaging to about 200 for chest imaging. The doses are of equivalent order to those from nuclear medicine studies or conventional angiography. However, manufacturers have invested considerable effort into minimising the radiation dose delivered by their scanners whilst optimising image quality (see Technical considerations). Basic principles of CT scanning CT scanners are used to image the internal structures of the body. They provide detailed anatomical information by utilising the principle that different types of tissue, depending on their composition and density, absorb varying amounts of X-rays. The structures scanned are displayed in the image as different shades of grey. Intravenous or oral contrast media may be used to further enhance discrimination between tissues. The basic components of a CT scanner are an X-ray tube and an arc of detectors, mounted on a gantry with a circular aperture (Figure 1a). Along the patient long axis there are many rows of these arcs of detectors, giving rise to the term multi-slice CT (Figure 2). Multirow CT, or multidetector CT (MDCT) are also commonly used terms. The extent of patient coverage by the detector rows currently ranges from 12 mm to 160 mm in length, depending on the scanner model. CEP08007: March 2009 Introduction 5 Figure 1. Schematic diagram of the CT scanner (a) ‘end view’, and (b) ‘side view’ in helical acquisition mode (a) (b) X-ray tube gantry X-ray tube patient table patient table Side view of detector banks arc of detectors 12 - 160 mm Power Data Figure 2. Multi-slice CT scanner X-ray beam and detectors (a) approximately to scale, and (b) schematic (a) (b) 12 - 160 mm each < 1 mm The patient lies on an integral couch and the X-ray tube and detectors rotate, continuously monitoring the absorption of X-rays as their path through the body changes. Image data can be acquired in sequential mode or in helical mode (Figure 1b). In sequential mode, sometimes known as axial mode or ‘step and shoot’, the couch is stationary during each rotation, then steps through the gantry to the next position in order to acquire another set of data. Some newer models have such an extent of coverage along the patient axis that for some studies only one rotation is needed. CEP08007: March 2009 Introduction 6 If the couch moves through the gantry at a steady rate, during the irradiation, whilst continuously acquiring attenuation data, this is a ‘helical scan’ (Figure 1b). This is also known as a spiral scan. CT scanner technology has advanced rapidly in recent years, moving to more powerful X-ray tubes, more efficient and stable detectors, more refined engineering and data acquisition systems and electronics, and faster computers. These developments have been largely directed towards improvements in the ‘three Fs of CT scanning’: faster scanning of further lengths of the patient, using finer slices. As a result, CT has evolved from a slice-by-slice diagnostic imaging system into a truly volumetric imaging modality, where images can be reconstructed in any plane without loss of image quality. This has lead to the increased use of multiplanar and 3D display modes in diagnosis. Field of use Patients are referred to CT scanning from practically all clinical specialties. They may be referred as in-patients, out-patients, or from the accident and emergency department. CT can be used in diagnosis, to assess the effectiveness of treatment, and to guide or plan clinical intervention. The majority of CT scans are currently performed to obtain anatomical information on a wide range of organs and tissues, but there are increasing numbers of functional and interventional applications. Current common uses are: • neurology - intra-cranial examinations, including brain perfusion in stroke assessment, examination of sinus and ear canals, spinal investigations • oncology – diagnosis, staging, follow up and radiotherapy treatment planning • cardiology – including coronary angiography and calcium scoring • angiography – whole body including venous, brain carotid, thorax, EVAR (endovascular aortic aneurysm repair) planning and follow up, and peripheral run-off • thoracic – evaluation of acute chest pain or dyspnoea and diffuse lung disease • virtual endoscopy – including colonography and bronchoscopy • orthopaedics - including surgical planning • trauma • image-guidance of interventional procedures – eg biopsy, drainage and RF ablation. CEP08007: March 2009 Introduction 7 Each trust will have identified the CT investigations it undertakes as part of its diagnostic imaging service, based on the current CT capabilities and availability of other local diagnostic services. Clinical impact As a key element within the diagnostic imaging department, the purchase of a CT scanner will have a major impact on the provision of services within the hospital. The new scanner may enable specialist investigations to be undertaken that were previously referred externally, and may also reduce the demand on other modalities. It can therefore impact upon healthcare targets such as the Department of Health (DH) 18 week referral to treatment time (RTT) target [1], which includes a 6 week target for time of referral to diagnostic procedure. The generally non-invasive nature of CT eliminates the need for hospitalisation due to possible morbidity resulting from invasive procedures such as angiography and endoscopy. Both CT angiography (CTA) and CT colonography (CTC) investigations have benefited from the advances in MSCT technology. CT angiography is becoming the method of choice for the investigation of suspected pulmonary embolism [2], and in cardiac CT angiography (CCTA), significant improvement in diagnostic performance has been shown for 16 and 64 slice scanners, compared with 4 slice devices [3]. CT colonography (CTC) is also gaining rapid clinical acceptance [4], and is more tolerable for patients compared to conventional colonography [5]. MSCT scanners have significantly reduced scan times, minimising motion artefacts. The acquisition of longer volumes, with finer slices, has improved image quality, enhancing 3D resolution. National guidance The Royal College of Radiologists (RCR) has published guidance on which examinations are best suited to CT [6]. The National Institute for Health and Clinical Excellence (NICE) [7] and the Department of Health (DH) have also issued guidance; key recommendations are summarised in Table 2. CEP08007: March 2009 Introduction 8 Table 2. NICE and DH guidance - key recommendations Issuer Investigation Summary of recommendation NICE Head Injury [8] Scan within either 1 or 8 hours of request, depending on risk factors NICE CT colonography [9] To replace conventional colonoscopy and double contrast barium examinations NICE Lung cancer [10] Follow up to abnormal chest X-ray to confirm staging of disease DH Stroke [11] Scan in next available slot for requests during working hours Scan within 1 hour for requests out-of-hours There is also guidance associated with the use of personally initiated CT scans for the health assessment of asymptomatic individuals, published by COMARE (Committee on Medical Aspects of Radiation in the Environment) [12]. For these circumstances, CT is not generally recommended, although certain allowances, under strict conditions, are made for coronary calcium scoring and colonography. CEP08007: March 2009 Technical considerations 9 A good understanding of technical considerations will underpin selection of an appropriate CT scanner. Technical specifications available for CT scanners are often quite extensive. Although it is helpful to review these for each scanner component, such an exercise may not reflect the relative clinical performance of the systems. The detailed specifications provide a guide to the level of performance expected and can highlight differences between manufacturers. These are given in the accompanying CEP Comparative specification reports [84]-[89]. However it is also important to recognise that the performance in practice will depend on the trade-off between image quality and radiation dose. Each system should therefore also be assessed in terms of the clinical, output-based specification it can meet, with an observation of the radiation dose utilised, and this is often best done in conjunction with a site visit (appendix 6). Key technical factors impacting on clinical performance are described in this chapter. Differences between categories of MSCT scanners (ie 16 slice, 64 slice etc) are highlighted, as well as the impact of new technological developments, particularly in their contribution to the advancement of the ‘three Fs of CT scanning’: to scan faster, further, and with finer slices. Figure 3 illustrates the rapid pace of developments in scanner technology over the last twenty years, and especially the acceleration of development in the last ten years from four to 320 slice scanners. Figure 3. Technological advances in CT scanner technology, 1985 - 2008 1989 2002 1995 2004 <1s 32, 40, 64 x 16 x 85 86 87 88 Slip rings, 1 s scan 89 90 91 92 Dual-slice 93 94 95 96 64 slice 16 slice < 1 sec scan Helical scanning (up to 32 mm coverage) 97 98 Four-slice 99 0.5 s scan 00 01 02 03 (up to 40 mm coverage) 04 05 06 07 256 slice, 320 slice Eight slice (80 mm, 160 mm coverage) 8x 320 x 0.5 s 1s 1985 1991 CEP08007: March 2009 1998 08 2001 2007 Technical considerations 10 Total scan time and scan length Clinical requirements The time taken to complete a scan is a key factor in scanner performance and may limit the type of procedure that can be performed. In most cases, the limitation is set by the need to control artefacts due to voluntary or involuntary patient motion; such as restlessness, or breathing and peristalsis. The acceptable scan time is dependent on the type of procedure, and patient status: for example in a CT pulmonary angiography (CTPA) scan, the scan must be completed within the patient’s breath-hold. Paediatric, geriatric and trauma patients may be unable to remain still for an appreciable time, and therefore a fast scan may preclude the need for an anaesthetic. Cardiac scanning is a particular example of the need for a short overall scan time as well as a fast rotation time. In contrast studies, the transit rate of contrast medium through the volume of interest will determine the acceptable scan time. Scanner design factors which affect the total scan time are the gantry rotation time and detector array design along the z-axis (scan axis). The maximum scan length achievable is another important factor in scanner performance, and may also limit the ability to perform certain procedures, for example when scanning peripheral angiography ‘run-offs’. Another aspect of maximum scan length that may need to be considered is the coverage available in dynamic studies such as CT perfusion scanning, where the same volume of patient is repeatedly scanned in quick succession. The maximum scan length is governed by the z-axis detector array design, and the X-ray tube heat characteristics. With the large volumes of data generated with a 64 slice scanner, for example, the total scan length may also be limited by computer memory capacity. Gantry rotation time The rotation time of the tube and the detectors around the patient (also know as gantry rotation time) clearly has a direct effect on total scan time. Image quality will improve with faster rotation times, as there will be reduced misregistration of data (both in-plane and along the patient) arising from patient movement (whether from heart beat, breathing, peristalsis, or restlessness). This misregistration of data introduces artefacts into the image. Scanners can now achieve rotation times of less than 0.3 seconds, but the fastest rotations are generally reserved for specialist applications such as cardiac scanning in order to minimise image artefacts due to the motion of the heart. The scanner that CEP08007: March 2009 Technical considerations 11 is available with two tubes, mounted at 90 degrees to each other, requires only a half rotation of data, so is effectively even faster. This has specialist cardiac applications. For general body scanning, 0.5 second rotations are usually more than adequate, and for head scanning, 1 second rotation times are often sufficient. Higher tube currents will be required for these faster rotation times, and when combined with long scan lengths there will be a need for a high anode heat capacity or high anode cooling rate. This effect is off-set by the use of longer detector array lengths. Detector array length 64 slice scanners cover a patient volume between 20 and 40 mm in length per rotation, and the latest diagnostic MSCT scanners can image patient volumes of up to 160 mm per rotation. The length of detector array will determine the number of rotations needed to cover the total scan length, and thus the overall scan time. The example in Figure 4 shows how the total scan time will be halved by doubling the array length .The ability to scan a given length with fewer rotations also helps to minimise heat load on the X-ray tube, thereby allowing the scanning of longer lengths. Figure 4. Effect of detector array on number of rotations and scan time eg 20 mm eg 40 mm Detector arrays are broadly divided into two types; ‘fixed’ and ‘variable’, sometimes known also as ‘matrix’ and ‘hybrid’. Fixed arrays have detectors of equal z-axis dimension over the full extent of the array, whereas on variable arrays, the central portion comprises finer detectors. With variable arrays, the total scan time for a given length, for the finest slice acquisition, will be longer, because the z-axis coverage is reduced (Figure 5). CEP08007: March 2009 Technical considerations 12 Figure 5. Example of 16 slice detector with reduced coverage for fine slices 4 x 1.25 16 x 0.625 4 x 1.25 10 mm 16 x 0.625 mm 4 x 1.25 16 x 0.625 4 x 1.25 20 mm 16 x 1.25 mm Examples of a range of actual detector configurations for different manufacturers are shown in Figure 6 (all detector array designs are given in the Market review). This figure illustrates that there is no fixed pattern when manufacturers move from 16 to 64 slice systems. Manufacturers A and B changed from a variable to a fixed array design. However, manufacturer A doubled the length of the detector array, whereas manufacturer B kept the same length. Manufacturer C retained the variable array design for their initial 64 slice scanner, with little change in the overall array length. Not shown is their newest design where they kept the same length but changed to the fixed array; that is detectors of all the same dimension. All the scanners available with greater than 64 slice acquisition have a fixed array. The evolution of designs reflects different strategies to accommodate future developments and allow for production costs. There is also some small dose saving where larger detector elements are used on the lower slice category scanners CEP08007: March 2009 Technical considerations 13 Figure 6. Examples of fixed and variable z-axis detector arrays (a) 16 slice scanners (b) 64 slice scanners Manufacturer A: Variable array Coverage: Full - 20 mm Sub-mm - 10 mm Manufacturer A: Fixed array Coverage: Full - 40 mm Sub-mm - 40 mm Manufacturer B: Variable array Coverage: Full - 32 mm Sub-mm - 8 mm Manufacturer B: Fixed array Coverage: Full - 32 mm Sub-mm - 32 mm Manufacturer C: Variable array Coverage: Full - 24 mm Sub-mm - 12 mm Manufacturer C: Variable array Coverage: Full - 28.8 mm Sub-mm - 19.2 z-axis Complete coverage of an organ, such as the brain or the heart, offers advantages for both dynamic perfusion and cardiac studies. The z-axis detector array lengths on the current 64 slice scanners, of up to 40 mm, are adequate to cover these organs in only a few rotations. A coverage length of 160 mm usually allows complete organ coverage in a single rotation, so the function of the whole organ can be monitored over time. Techniques have recently been developed to extend the effective coverage for dynamic perfusion studies on scanners where the whole organ, or required part of the organ, is not completely covered by the detector array. There are two approaches to this. One is to perform consecutive, sequential scans by repeatedly ‘jogging’ the patient couch between two z-axis positions, effectively doubling the length of organ that can be monitored. The second approach is to perform a ‘helical shuttle’ scan, whereby the organ is scanned in helical mode in alternating directions. The length of coverage in this mode is dependent largely on the frequency with which the organ needs to be monitored. CEP08007: March 2009 Technical considerations 14 Figure 7. CT perfusion with ‘jog’ or ‘shuttle’ scan 40 mm detector 80 mm coverage X-ray tube Modern CT scanning techniques place a high heat load on the X-ray tube due to the need for high tube current values (mA) in order to give enough photons in the image when scanning with fast rotations and fine slices. Increasing rates of obesity in the UK mean that the size of the average patient is an added burden on the X-ray tube, as higher tube currents need to be used in order to generate enough photons to give reasonable image quality. To scan a sufficiently long length, whilst avoiding overheating, X-ray tubes have generally been developed to have high anode heat capacities and high cooling rates. Some designs have low anode heat capacities, but very high cooling rates to compensate. These two specifications, heat capacity and cooling rate, therefore need to be considered jointly to assess the overall heat load capability. Implications in clinical practice can be enquired of during site visits. Some designs that improve cooling rates are spiral-groove bearings with liquid metal lubrication, and anodes with direct oil cooling. Image quality The principal parameters that describe image quality are spatial resolution, contrast resolution, temporal resolution, and the prevalence of artefacts. Manufacturers provide performance specifications on spatial resolution and contrast resolution. The International Electrotechnical Commission (IEC) has issued standards relating to the CEP08007: March 2009 Technical considerations 15 measurement of some of these parameters [13],[25]. However, for some parameters, particularly those for contrast resolution, these can be difficult to compare between different systems, due to the differing methodologies employed. All manufacturers will have some approaches to artefact reduction, depending on the type of artefact. Little objective comparative information, if any, is provided by manufacturers with respect to artefacts, as there are no standard methods for their quantification. The image quality actually achieved on any scanner will depend not only on scanner design features, but also on scan parameters selected and patient-related factors, and will always be a compromise between image quality and radiation dose. The following sections deal with the impact of scanner design features on image quality and radiation dose separately. It is therefore important to be supported through the equipment selection and procurement process by the local medical physics service, who should be invited to assist during site visits with objective and subjective comparisons of image quality, together with the radiation dose required to produce the image. Spatial resolution Spatial resolution is the ability of the system to image an object without blurring. It is often described as the ‘sharpness’ of an image (Figure 8). It may be quoted as the smallest object size able to be discerned, and as such is evaluated using high contrast test objects where signal to noise level is high and does not influence perception. It can also be specified in terms of spatial frequency, in line pairs per cm (lp/cm), for particular levels of the modulation transfer function (MTF); usually at the 50%, 10% and 2% or 0% levels. The 0% MTF level is referred to as the ‘cut-off frequency’ and reflects the limit of the spatial resolution. The visual limit of spatial resolution, as the minimum size of high contrast objects, in millimetres, that can be distinguished, more generally relates to the frequency values between approximately the 2 and 5% modulation of the MTF. Sometimes a visual limit value is given by the manufacturers, either from a visual test object, or by converting the 2% value on the MTF to its size in mm. Modern MSCT scanners should be capable of achieving isotropic resolution: a z-axis resolution that is equal to, or approaching, the scan plane resolution, as this is essential for good quality multiplanar and 3D reconstructions. In practice, it is helpful to remember that the cost of high spatial resolution is either in high image noise, or in high radiation dose when the tube current is raised to reduce the image noise. CEP08007: March 2009 Technical considerations 16 Figure 8. Test object with line pairs of varying frequencies for assessment of scan plane spatial resolution 11 lp/cm 13 lp/cm 10 lp/cm 12 lp/cm 9 lp/cm The following scanner design features affect the x-y plane spatial resolution: • • • • • • • • focal spot size (x-dimension) focal spot stability detector size (x-dimension) number of ‘views’ per rotation (sampling frequency) ‘over-sampling’ techniques quarter-detector shift flying/dynamic focal spot attenuating grid (x-y plane) The focal spot size and detector size determine the ‘sampling aperture’. The sampling frequency is the number of times data from the detectors is ‘read’ during a rotation, and together with the sampling aperture determines the sampling density, ie how finely the object is sampled. Over-sampling techniques are aimed at further enhancing the spatial resolution by sampling the object at intervals smaller than the sampling aperture. All modern scanners employ the quarter-detector shift approach, in which data from the second 180° of each rotation are off-set from the first 180° (Figure 9a). Some manufacturers also use a dynamic or flying focal spot, effectively obtaining two sets of data, or ‘views’ at each angular sampling position, increasing the sampling density still further (Figure 9b). CEP08007: March 2009 Technical considerations 17 Figure 9. Diagram of methods for improving sampling density (a) quarter-detector shift, (b) flying focal spot (a) (b) For the highest spatial resolution, such as that required for imaging the internal auditory canal, a technique using an attenuating grid or ‘comb’ is available on some scanners (Figure 10). This grid effectively reduces the detector size but should be used only when necessary, as it reduces dose efficiency. In other words; the image noise is increased for the same patient dose, or the tube current can be increased to compensate, reducing the noise but increasing the patient dose. Figure 10. Reduction of effective detector size with attenuating grid Attenuating grid Detector bank Any unplanned movement of the focal spot will cause additional blurring and reduce spatial resolution, and this can be a particular problem with fast rotation speeds. Developments in X-ray tube technology, such as dual-support anodes and segmented anodes are aimed at improving focal spot stability. CEP08007: March 2009 Technical considerations 18 The z-axis resolution is often referred to as z-sensitivity and is quoted in terms of the full width at half maximum (FWHM) of the imaged slice dose profile, but it may also be determined by the MTF. It is governed by similar factors as the x-y plane resolution: • • • • • • • focal spot size (z-dimension) focal spot stability detector size (z-dimension) ‘over-sampling’ techniques optimal pitch values z-axis flying/dynamic focal spot attenuating grid (z-axis) The z-axis resolution is primarily determined by the z-axis detector dimensions. Z-axis detector array design on MSCT scanners varies considerably between systems, with minimum dimensions ranging from 0.50 to 0.75 mm. As described earlier, some arrays are fixed design, whilst others are a variable design (Figure 6). With variable arrays, the z-axis spatial resolution will be reduced when the full extent of the array is used for imaging, as data from adjacent detectors are combined, increasing the effective detector size. Contrast resolution Contrast resolution is the ability to resolve an object from its surroundings where the CT numbers are similar (eg in the imaging of liver metastases). It is sometimes referred to as low contrast resolution or low contrast detectability. The ability to detect an object will be dependent on its contrast, the level of image noise and its size. Contrast resolution is usually specified as the minimum size of object of a given contrast difference that can be resolved for a specified set of scan and reconstruction parameters (Figure 11). Figure 11. Test object for contrast resolution measurements CEP08007: March 2009 Technical considerations 19 Generator power is an important factor in low contrast examinations. Low noise images require high tube current (mA) values, particularly when coupled with fast rotation speeds and narrow slice acquisitions. Fast rotation speeds reduce movement artefacts, thin slices improve spatial resolution as well as reduce partial volume effects. Dose efficiency of the scanner is a significant factor in these types of examinations, as it will determine the dose required for a given level of contrast resolution. Contrast resolution specifications should give a guide to a scanner’s dose efficiency. However, there is no standard methodology of data acquisition and image quality scoring to enable a good comparison of manufacturers’ data. Temporal resolution In CT, temporal resolution is usually considered in the context of cardiac scanning. The aim, in cardiac CT, is to minimise image artefacts due to the motion of the heart. This can be achieved using ECG-gating techniques, and imaging the heart during the period of least movement in the cardiac cycle, for a time interval of about 10% of the cycle. This results in a temporal resolution requirement of about 100 ms for a heart rate of 60 beats per minute. The temporal resolution is defined as the time taken to acquire a segment of data for image reconstruction. For ‘single segment’ reconstruction, it will be the time taken to acquire180° of data, ie the time for half a gantry rotation. However, for higher heart rates this can still result in unacceptable cardiac motion artefacts. In this situation data from multiple, smaller segments, acquired from successive rotations, can be summed in order to obtain the 180° dataset (Figure 12). Using the multi-segment reconstruction approach requires an asynchrony between the gantry rotation and the patient’s heart rate so that data from the successive segments are not acquired at the same angular positions. There is an optimum combination of pitch, gantry rotation time, and number of segments for a given heart rate. Manufacturers’ software may have a combination of automatic and semi automatic adjustment of these parameters with differing amounts of user input required. Some manufacturers’ software automatically adapts the gantry rotation speed to the heart rate, others have automatic algorithms for calculating pitch and the number of multi-segments. CEP08007: March 2009 Technical considerations 20 Figure 12. Principle of multi-segment reconstruction in retrospectively gated CCTA Low pitch helical scan Temporal resolution 200 ms Single segment 100 ms Two segments ~ 70 ms 50 ms Four Three segments segments Although multi-segment reconstruction provides a method for improving the temporal resolution, it is prone to mismatch artefacts, particularly for unstable heart rates. Single segment reconstruction is therefore the preferable approach, requiring scanners with high gantry rotation speeds. Another approach to improving temporal resolution is with multiple X-ray sources. A scanner with two X-ray tubes and two detector arrays is currently available (Figure 13). The two assemblies are positioned orthogonally in the scan plane and simultaneously acquire a 90° segment of data. In this way, a temporal resolution of quarter of the rotation time is achieved, thereby improving the temporal resolution by a factor of two compared to a single source system using single segment reconstruction. CEP08007: March 2009 Technical considerations 21 Figure 13. Schematic diagram of a dual source CT scanner Image artefacts Artefacts are defined as structures in the image that are not present in the object. An imaging system will invariably produce some level of artefact, but it becomes an issue if it obscures an abnormality, resulting in a false negative diagnosis, or mimics an abnormality, giving a false positive result. Artefacts can be due to patient factors, scanner design factors or the reconstruction process, which by necessity involves some approximations. Image artefacts commonly encountered are due to: • • • • • • • patient motion partial volume photon starvation metal objects beam hardening helical scanning cone-beam geometry. For MSCT scanners, patient motion and partial volume artefacts will generally be reduced due to the decreased scan time and the ability to acquire with narrow slices. Photon starvation artefacts, ie streaks arising from the high attenuation in lateral projections of areas such as the shoulders and pelvis (Figure 14) can be reduced with angular tube current modulation (see Ionising radiation and patient dose below). Other artefacts, such as those resulting from the extended X-ray beam along the z-axis, will be increased. These are generally referred to as ‘cone-beam’ artefacts. CEP08007: March 2009 Technical considerations 22 Figure 14. CT scan through the shoulders, demonstrating photon starvation artefacts Traditional back-projection methods of reconstruction in CT assume parallel-beam geometry in the y-z plane. As the z-axis beam extent is increased, this assumption breaks down and ‘cone-beam’ reconstruction methods must be used to avoid excessive artefacts. Some manufacturers employ adaptations of the back-projection approach, whereas others use 3D methods such as approximations of the Feldkamp reconstruction [14], [15]. Although 3D methods are more exact, they may require longer reconstruction times. Cone-beam reconstructions are generally only implemented in helical scanning, therefore in sequential scanning, the extent of beam used, or the narrow slice reconstructions, may be limited. The latest scanners, with beam extents of 80 mm to 160 mm, by necessity also use cone-beam reconstruction methods in sequential scan mode. Ionising radiation and patient dose As with any imaging modality involving the use of X-rays, The CT scanner and its use, falls under both The Ionising Radiations Regulations,1999 (IRR 99) and The Ionising Radiation (Medical Exposure) Regulations, 2000 (IR(ME)R 2000) [21],[22]. Scanners have different design and safety features that affect the level of radiation dose. These will need to be considered at the time of purchase, and also in the operation of the scanner. Doses from CT examinations are generally significantly higher than those for conventional X-ray, although a CT scan provides more diagnostic information. The CT doses may be typically factors of 10s higher for standard head and abdomen examinations, and factors of 100s for chest examinations [20]. Recent UK surveys report conventional X-ray examinations with average doses of 0.04 mSv for head examinations, 0.7 mSv for abdomen, and 0.02 mSv for chest examinations [16],[18]. A similar survey for CT examinations gave values of 1.5, 5, and 6 mSv respectively for the same examination regions [17]. These figures represent average values from the use of a wide range of operational parameters, such as tube current and voltage, however they can be used as a guide. CEP08007: March 2009 Technical considerations 23 Doses in CT are of the order of those received in nuclear medicine studies and interventional X-ray [19],[20]. The standard reference parameters used to describe dose in CT are the CTDIvol (volume computed tomography dose index) and the DLP (dose length product). The CTDIvol is calculated from measurements, made with a 100mm long pencil ion chamber, in standard sized polymethymethacrylate (PMMA) head and body phantoms which have been irradiated at the halfway position, along the length, with a single beam rotation. However, as a dose descriptor, it is important to think of the CTDIvol as representing the average dose in a slice of tissue, halfway along a 100 mm irradiated length. The DLP represents the total amount of irradiation given, and as such gives an indicator of risk (without taking into account the radiosensitivity of particular organs). The CTDIvol is a very useful dose descriptor for comparing dose from different protocols or different scanners. However comparisons should only be done for scans undertaken on standard size patients. Figure 15. a) PMMA body phantom used for measurement of CT doses b) illustration of CTDIvol representing average dose at central slice position of 100mm irradiation length (a) (b) equivalent to an irradiation length 100 mm CTDIvol represents average dose at central slice position standard size Perspex phantom The CTDIvol (and sometimes the DLP) values are displayed on the scanner console. It is always invaluable to look at these figures when reviewing patient images for an assessment of the image quality and dose performance of a scanner. Both the CTDIvol and the DLP are used when comparing with dose reference levels (DRLs) [22],[17]. MSCT scanners have the potential to give higher radiation doses compared to single slice scanners. Their flexibility in scanning long lengths with high mAs values, and the ease with which they perform dual and even triple-phase contrast studies, can CEP08007: March 2009 Technical considerations 24 lead to high patient doses. In addition, there are some intrinsic features of current MSCT design which can give rise to slightly higher doses and these are discussed below. Manufacturers have invested a great deal of effort in measures to minimise radiation dose. Nevertheless, the optimisation of scan protocols, in order to keep doses as low as reasonably practicable (ALARP), is a legal obligation [21][22]. This is of particular importance in paediatric studies. Over-beaming Over-beaming in MSCT is the extent of the X-ray beam penumbra along the z-axis which is not utilised for imaging, so the true irradiated volume per rotation is greater than the nominal imaged volume. It is quantified in terms of geometric efficiency (GEff), and the user is alerted by a display on the console if a scan protocol results in a GEff of less than 70%. Over-beaming is necessitated in MSCT so that all active detectors are exposed to the same intensity of X-rays. The extent of the penumbra is generally 2 to 3 mm either side. For narrow z-axis beams, the over-beaming will therefore affect the dose significantly. For example, with a nominal imaged length of 2 mm, the actual irradiated length will be 4 to 5 mm, resulting in a doubling of dose or more, compared with a single slice scanner where only 2 mm would be irradiated. As the extent of the beam increases, this penumbra is proportionately less significant (Figure 16), so that for nominal collimations of 20 mm or more, GEffs comparable to those on single slice scanners are achieved. Figure 16. Reduced influence of over-beaming for larger z-axis beam collimations z-axis CEP08007: March 2009 Technical considerations 25 Reduced X-ray beam collimations (and therefore lower GEff) are required on scanners with adaptive arrays, when acquiring narrow slices. Scanners with fixed arrays will therefore have dose advantages, as they can utilise the full extent of the array for narrow slice acquisition. Over-ranging in helical scanning Irradiation extending beyond the imaged length is required in helical scanning. This over-ranging results from the extra rotations necessary for reconstruction of the first and last images in the imaged volume. Their contribution to patient dose becomes more significant for wider z-axis beam collimations (Figure 17). Therefore, the increase in dose contribution with wide collimations from over-ranging counteracts the improvements in dose efficiency of over-beaming. The increase in dose from over-ranging is particularly significant for short scan lengths, and at some point it is preferable to reduce the collimated beam, or even to use sequential scan mode if examination time is not an issue. Sequential scan mode may also be preferred in order to avoid certain radiosensitive organs at the beginning and end of the imaged volume. Figure 17. Increased dose contribution from over-ranging with wider X-ray collimations Extra rotations Imaged volume Some manufacturers have sought to address the problem of excess dose from overranging, and certain scanner models have a feature which dynamically adjusts the beam collimation at the beginning and the end of a scan to minimise the dose whilst still allowing full reconstruction of the required imaged volume (Figure 18). The total dose savings depends on the length of the scan, the X-ray beam collimation, the rotation time and the pitch, but are estimated to be between 10 and 25%. CEP08007: March 2009 Technical considerations 26 Figure 18. Dynamic collimation to reduce dose at the extremities of a scan X-ray beam Dynamic collimators Dose saving Imaged volume Automatic tube current control in CT Traditionally, the X-ray tube current (mA) in CT was selected for a particular protocol, and remained constant throughout a scan. Any changes to accommodate differentsized patients had to be estimated, and implemented manually. Modern scanners are equipped with automatic exposure control mechanisms, which adjust the tube current for changing patient attenuation throughout a scan. The adjustment can be made to compensate for changing attenuation (Figure 19): (a) in different-sized patients; (b) along the patient’s long axis; and (c) throughout a gantry rotation. Most modern systems have the capability to operate all three compensation modes, which are generally implemented simultaneously. Most scanners will allow manual de-selection of one or more modes, and on others the de-selection may be implemented automatically within a protocol, according to the clinical region scanned. Figure 19. Automatic tube current control in CT (b) (a) (c) mA High mA High mA Low mA CEP08007: March 2009 Low mA Technical considerations 27 Cardiac scanning Dose considerations are a particular issue in cardiac scanning. A standard chest CT scan would give an effective dose of approximately 6 mSv [17], whereas effective doses for cardiac CT angiography (CCTA) scans, using retrospectively gated reconstructions from low pitch, helical scans, are typically about 16 mSv, but can be much higher, with 32 mSv being reported in the literature [20]. To reduce doses for these types of scans, manufacturers have introduced ECGgated tube current modulation on their cardiac-enabled scanners (Figure 20). Outside the cardiac phase used for reconstruction, the tube current can generally be reduced to 20% of its peak value, although one range of scanners allows a reduction down to 4%. ECG-gated tube current modulation is only effective for patients with stable heart rates. Figure 20. ECG-gated tube current modulation ECG signal Tube current Imaging window 100% 20% Another approach for reducing doses in CCTA is to use prospectively gated sequential scanning, where the tube current is only switched on during the cardiac phase of interest. Prospectively gated reconstruction has been used for some time in cardiac calcification scoring, but not in CCTA, as the thinner slice acquisition required led to reduced beam collimation and extended the examination time unacceptably. However, on some scanners of 64 slices and above, prospectively gated CCTA scans are possible. Although prospective gating has potential for large dose reductions it requires a steady heart rate for good results as the examination time is increased. However, the wide beam acquisition systems that can acquire the whole imaged volume in one rotation can employ prospective gating with unstable heart rates. New and future applications Dual energy applications Dual energy applications in CT are still evolving. They are aimed at identifying and discriminating between materials of similar CT number, such as soft plaque and fatty tissue, or calcified plaque and contrast media. They make use of the differing CEP08007: March 2009 Technical considerations 28 chemical composition and attenuation properties of the materials, and the change with different X-ray energies. There a number of ways in which dual energy scanning can be implemented. One manufacturer’s dual source (two tube) system employs one tube operating at 80 kV and the other at 140 kV, to acquire data at the two energies almost simultaneously. An approach being developed by another manufacturer with a single X-ray tube scanner, alternates the tube kV at half rotation intervals. A third manufacturer has developed a dual-layered detector to discriminate between energies. The top-layer detects the low energies, and the bottom layer the higher ones. The dual source method currently has the most highly developed clinical applications. Future proofing the decision The rate of change of CT scanners has been high in the last few years, and if it sustains this rate of growth it is difficult to predict what the forthcoming years will bring. However it is always important to discuss upgrade options with the manufacturer. Some systems are on a clear upgradeability path, particularly if a lower specification model has been purchased. For example the lower slice category scanners with fixed arrays can theoretically be easily upgraded to a higher slice category without a change of detectors, though with other software and some changes required. Upgrade paths, however, are often much more complex than this, and some may be more of a ‘fork lift’ upgrade, in that the whole system will be replaced. Each manufacturer should be asked for a clear description and potential costs. The longer arrays (80 mm, 160 mm), announced at the end of 2007, have brought greater capability in cardiac scanning and in perfusion studies, and further applications are developing. These scanners, as high cost, high performance scanners, are currently regarded as specialist systems, and are likely to remain so for a number of years. Sustainability Intrinsically MSCT is more energy efficient as the wider coverage requires fewer rotations for a given scan length, resulting in lower X-ray tube heat load and longer tube life. In practice, this energy and tube life saving may not be achieved due to changes in scan protocols. Developments in tube technology, such as spiral-groove bearings with liquid-metal lubrication and anodes with direct oil cooling, can also extend tube life. Some systems have contactless transmission for data transfer, which eliminates the need for carbon brush replacement. One scanner has a slip ring design with airbearings which might also reduce maintenance requirements. CEP08007: March 2009 Operational considerations 29 This chapter addresses the operational issues which impact on selection of a multislice CT scanner (Table 3). Table 3. Operational issues affecting MSCT selection Area Aim Topic / issue Scanner installation Effective installation Scanner location Room requirements Ancillary equipment Ergonomics Acceptance and commissioning Training Decommissioning Ongoing considerations Maintaining quality and providing service Periodic maintenance Consumables Quality Assurance (QA) Efficient patient throughput Staffing Referral Scheduling Patient preparation Scan set-up Image reconstruction Further processing Specialist applications Efficient processing and reporting CT scanner workstations PACS workstation Remote access client Reporting Data management Interoperability Integration with other hospital systems Systems integration Existing modalities Specialist systems Information security Safety Safe working practices Ionising radiation Infection control Patient workflow Information workflow CEP08007: March 2009 Operational considerations 30 Installation Overview To ensure an efficient and effective installation process, it is recommended that a project manager be appointed to manage the project to completion. A CT scanner requires supporting infrastructure that is wide ranging. The estates department, the IT department, the local radiation protection advisor, and PACS or RIS (radiology information system) managers should all be involved in planning the installation. Plans for scanner suites should also be checked with local infection control officers. Consideration must be given to continuity of clinical services during the installation and commissioning period. Options include use of a mobile CT scanner, either supplied by the trust or by the manufacturer as part of the purchase agreement. Scanner location There may be little flexibility in the location of the scanner suite, for example, where an existing scanner is to be replaced. However, a formal assessment of benefits of building in a new location should be undertaken. If an existing facility is being reused, it should be properly assessed before the scanner installation commences, with consideration to any revised requirements due to changes in the scanner, the use, or the workload. Where there is choice of location, then ease of transfer of patients to the scanner suite is a primary consideration. Certain departments (eg accident and emergency, neurological ITU) are likely to require more frequent access to CT scanning facilities than others. Access routes for both inpatients (including bed access) and outpatients should be straightforward. Separate areas may be required for patient cannulation, and for reporting workstations. Where more than one scanner is in use, a single shared control room can improve efficiency. The room must have sufficient radiation shielding for a CT scanner. These calculations must be ascertained early in the purchasing process. The local RPA would need to be involved in this process. Room requirements Most manufacturers can provide a checklist of installation requirements in advance. These should be obtained as part of the tendering process. Additional works required to meet these requirements may need to be factored into the overall cost. CEP08007: March 2009 Operational considerations 31 The scanner must be housed in a room which is large enough to ensure ease of access for patients and clinical staff, with a floor strong enough to withstand the applicable loading. There must be sufficient access for an emergency (crash) trolley for cardio-pulmonary resuscitation. Air conditioning may be required to ensure consistent scanner operating temperatures, and the comfort of patients and staff. This should be sited appropriately so as to avoid damage to the scanner from condensation. Additional ventilation with suitable extraction rates may also be required if medical gases or insufflators are used. Attention should be paid to the provision of adequate lighting within the scanner room. Areas housing reporting workstations will have their own specific lighting requirements. Power requirements are specified by the manufacturer. It may be necessary to upgrade the main supply to the scanner suite before installation. Due to the large amount of power required, CT scanners are not normally connected to the uninterruptible power supply (UPS). However it may be possible to connect to a UPS that gives sufficient time to allow normal shutdown procedure of the CT scanner without a system crash. CT scanning is subject to The Ionising Radiations Regulations, 1999 (IRR 99) [21], and The Ionising Radiation (Medical Exposure) Regulations, 2000 (IR(ME)R 2000) [22]. The use of the rooms neighbouring the scanner suite may impose additional constraints. A radiation protection advisor should be consulted at an early stage to ensure that any such additional constraints are taken into account in calculating the radiation shielding requirement for the walls and ceilings. Even if a new scanner is being installed in a room previously occupied by a CT scanner, consideration must be given to any change in dose rates. Scatter dose rates on multi-slice scanners will generally be larger than for single slice scanners as the radiation coverage is wider for a single rotation. Multi-slice protocols are also often likely to use thinner reconstructed image slices from the wide beam, resulting in possible increases in tube current and therefore higher scatter doses. Increased patient workload will also have a significant effect on scatter doses. Inadequately shielded scatter radiation can interfere with other equipment, such as gamma and PET cameras. Testing of existing shielding can confirm if this is a potential issue. CEP08007: March 2009 Operational considerations 32 Ancillary equipment As well as the scanner gantry and couch, other equipment may need to be located in the scanner room itself, or nearby. Manufacturers can supply details of ancillary equipment, such as computers and cooling plant, indicating any restrictions on where these can be located. Inside the scanner room some ancillary equipment can be ceiling mounted to give maximum free floor area. Storage for accessories and consumables needs to be included in the design of the scanner suite. Ancillary equipment commonly located in the scanner room includes: • • • • • contrast pumps, warmers, and associated supplies insufflator and applicators fluoroscopy systems (slave monitor, foot pedal) ECG systems life support systems / crash carts. Ancillary equipment commonly located outside the scanner room: • • • • • • CT workstation (for post processing and / or reporting) disc burning unit (MOD and / or DVD) RIS workstation (for patient tracking) PACS workstation (for other images and/or reporting) hard-copy device (for referral forms etc) histology station (for biopsies). Ergonomics The scanner should be positioned in the scanner room so as to allow free access around the couch and the gantry. The couch must be free of obstruction throughout its full range of motion. It should also be oriented such that staff at the console can see the patient at all times during the scan procedure, ideally through a shielded window. Some departments now use CCTV systems to view behind the gantry. Controls for the motion of the couch are often on both sides (left and right) of the aperture, allowing the operator to stand where it is most convenient. Some operators favour controls on both the front and back of the gantry. Foot pedals and couch side controls may also be available. In order to facilitate patient transfer, it should be possible to adjust the height of the couch to allow the patient to sit on to the couch. For in-patients, it is necessary to be able to position the bed closely alongside the couch at the same level. Once the CEP08007: March 2009 Operational considerations 33 patient has been transferred to the couch, the bed should be moved away to allow scanning staff full access to the patient. When support systems, such as ventilation, are required for the patient, there should be facilities to operate these within the scanning room. The scanner console should be designed to allow the staff to work appropriately. The height should be such that staff can operate the system seated or standing. The system should have minimal left and right hand bias. Software interfaces for the setup and review of the scan must be clear and easy to use. This is best assessed on site visits. Guidance for working on computer workstations has been prepared by the Royal College of Radiologists [23]. Any in-room accessories, for example contrast pumps, fluoroscopy monitors, should be fitted such that they do not interrupt the general work of the radiography staff. Ceiling mounted system options offer such an advantage, though they are more expensive. Storage of attachments and other occasional accessories should be such that there is no lifting hazard when handling. Critical examination, acceptance and commissioning Once the scanner has been installed it has to undergo a critical examination in accordance with the Ionising Radiations Regulations, 1999 (IRR 99) [21], [24]. The responsibility for this lies with the manufacturer, and must be carried out in conjunction with a radiation protection advisor (RPA) who may be appointed by the supplier, or the purchasing trust on behalf of the supplier. There is a need to establish, preferably at the contract stage, which RPA (the installer’s or the purchaser’s) will oversee the critical examination. In addition, the scanner will need to be formally accepted by the purchaser. This is to verify that the contractor has supplied all the equipment specified and has performed adequate tests to demonstrate that the specified requirements in the contract have been met. Some trusts will, subject to contract, withhold a percentage of the scanner price (eg 5%) until the scanner has passed the acceptance process. The acceptance process also covers electrical and mechanical safety, radiation protection issues, image quality, and dose performance. There are IEC guidelines available for this process [25]. It is worth considering the requirement of the provision of phantoms, for acceptance testing purposes, in the tender specification. CEP08007: March 2009 Operational considerations 34 All connectivity issues should also be assessed at this stage. (See Information workflow below.) The final stage of installation is commissioning the scanner. This comprises a set of tests carried out by the purchaser’s representative to ensure that the scanner is ready for clinical use and to establish baseline values against which the results of subsequent routine quality control performance tests can be compared. This is also the process whereby the users bring the system and its protocols to a state ready for clinical use, bearing in mind specific clinical applications and requirements. This may involve scanning phantoms, as well as patients with the attendance of the supplier’s clinical specialist. The same RPA may undertake the critical examination, acceptance and commissioning. However, although the tests may be combined, their purpose should remain distinct [29]. Training Under the medical exposures regulations, IR(ME)R 2000 [22], all who act as either operators or practitioners as defined by the regulations, i.e. anyone who either authorises the use of or delivers ionising radiation, are legally required to have received certified training. Also, in accordance with good clinical governance, it is essential that all staff using and supporting the use of the scanner and workstations are suitably trained. The requirements for such training need to be specified in the tender document. These will cover initial and ongoing training for all users, or for specific users responsible for cascading training to other staff. The training should cover the basic operation of the scanner, set-up and optimisation of scan protocols, and the function of advanced packages, where installed. Specialist workstation training will also be required for specific staff. The Royal College of Radiologists (RCR) has published guidelines for IT systems training in imaging departments. The general principles covered by this RCR document are also applicable to training in the use of a CT scanner [26]. Manufacturers generally offer training as part of the purchase package. Training on the scanner is usually offered in three phases: prior to the scanner installation; at the time of first patient scanning; and after a few weeks or months as follow up. Prior to scanner installation it can be helpful for staff to experience some basic training on a system in use elsewhere, and the manufacturer can often make arrangements for this. This might involve at least one member of staff spending a week at another site. CEP08007: March 2009 Operational considerations 35 For the second phase, an application specialist from the manufacturer will be present at the clinical site, to provide a mixture of training and support during initial patient scanning. Finally the manufacturer will commonly make provision for a specified level of applications specialist availability for future visits, to address training requirements for advanced functions and issues arising from normal clinical use. Training on the use of the scanner workstation and specialist software packages is commonly offered as a separate package for radiologists and other specialists. Some manufacturers offer training courses off-site for this purpose. In addition there will be some level of continuing support offered, after the warranty period, as part of a specific level of support contract. This is particularly helpful when introducing new applications, or for optimising the use of advanced features such as tube-current modulation. The relationship between the supplier’s applications specialist and the radiology department is important in optimising use of the scanner. It can be helpful to have specialist staff, such as medical physics experts (MPE) and radiation protection supervisors (RPS), involved in the training, particularly in the use of the specialist features such as those that either modulate radiation dose, or give high dose, such as fluoroscopy or cardiac scanning. Decommissioning At the end of service life, the scanner will need to be decommissioned. Manufacturers are working towards full WEEE compliance [27], and so will be able to remove and dispose of the scanner as appropriate. This might apply to the removal of an existing scanner, as well as the future decommissioning of the new purchase. Transfer of existing data may be an issue. Image data stored on a secondary system, such as a picture archiving system (PACS), will not need further migration. Other data may need to be transferred or archived for future access. Ongoing quality Periodic maintenance Scanners are generally serviced by engineers from the manufacturer. This is covered by a service contract, which is normally negotiated at the time of purchase. The service contract may cover a fixed number of years, or may be renewable annually. CEP08007: March 2009 Operational considerations 36 The type of service contract will depend on local needs to maintain a clinical service. There tend to be two or three levels of service agreement offered, with greater costs associated with increased availability of response, and inclusion of key hardware items, such as X-ray tubes or detectors. Frequency and duration of routine servicing vary with manufacturer and scanner, but normally takes up to one day, and occurs every three to six months. At this time the scanner is checked and any planned upgrade to components and software undertaken. Hardware and software updates often have implications for image quality and dose; therefore the local medical physics expert (MPE) and/or radiation protection advisor (RPA) should always be informed of these visits and given information of any upgrades installed. For unscheduled support, options are generally available for 24 hour access to an engineer, or for support only during office hours (08:00 – 17:00). Some manufacturers use remote access systems for an initial test of the scanner. Options for training local engineers in first line trouble-shooting may be requested in the tender document. When comparing reliability, or ‘up-time’ claims, it should be noted that these figures may not be defined in the same way between different manufacturers. It should also be noted that then impact of down-time on the clinical service will depend on the clinical investigations carried out, and the demand placed on the scanner. Consumables The main consumables of MSCT scanning are associated with contrast systems, and include contrast agent and saline, cannulae and injection lines for contrast delivery, and applicators for insufflation. Other consumables are ECG pads for cardiac scanning, paper roll bed liners, personal protective equipment, such as gloves and aprons, cleaning materials, and patient gowns (if single-use gowns are employed). Standard local procedures should be followed for the disposal of the clinical waste generated from these consumables. Storage devices such as magneto optical discs (MODs), compact discs (CD), or digital video discs (DVDs) may constitute significant consumables, dependent on how information transfer is handled (see Data management below). The X-ray tube may be included within the maintenance contract. If not included in a contract, it may be regarded as a consumable. The X-ray tube is covered by a warranty that is generally based on number of rotations or exposure time. It might be expected to last between a year and eighteen months, dependent on patient throughput and tube technology. The tube technology is a key difference between some of the CT manufacturers and claims of tube lifetime vary considerably. CEP08007: March 2009 Operational considerations 37 Quality assurance All scanners for use on patients must be subject to a documented quality assurance (QA) process, including quality control (QC) testing of the scanner, according to IRR 99 and IR(ME)R 2000 [21], [22]. There are published guidelines on the QC activities that should be undertaken [29] - [31]. This involves a combination of daily checks and more extensive routine testing. Daily tests are carried out before scanning commences, normally by the duty radiographers. The more extensive, less frequent, checks are undertaken by the local medical physics department. Manufacturers provide test objects for routine testing of the scanner. Additional test objects may be required to support other tests. These may be included in the tender package. Some scanners include special protocols and phantoms that automatically carry out such test scans. Time must be allowed within the installation plans to establish baselines for quality control measurements, preferably at commissioning The Ionising Radiation (Medical Exposures) Regulations, 2000 (IR(ME)R 2000) [22] states that records should be kept of the doses to patients. These should be subject to routine audit and comparison with national guidance in pursuit of optimisation of image quality and patient dose. There is general information on patient dosimetry available from the Department of Health [32], and specific CT dose data from the Health Protection Agency [17]. Patient workflow Introduction Improving access to key diagnostic tests has been identified as one of the ‘10 High Impact Changes for Service Improvement and Delivery’ [33]. The installation of a new CT scanner gives the opportunity to address changes in working practice within the department to improve efficiency and patient workflow. General workflow for a CT scan is shown in Figure 21. There are certain items directly affected by the choice of scanner, however the majority of issues affecting workflow are operational. Studies have found that increased patient throughput can be achieved with relatively simple changes in working practice [34], [35]. In one study, CT scan waiting times were reduced on average by 43 days across 23 pilot sites by matching demand and capacity and improving the flow of patients [33]. Key aspects [35],[36] to be addressed to improve patient workflow are: assigning a scan protocol at the acceptance of the referral; using an appropriate staff skill mix; CEP08007: March 2009 Operational considerations 38 cannulating the patient outside the scanner room; and having a booking system that is not dependent on in-patients arriving at specific times. These issues are further discussed below. Extending working hours can also improve workflow. However, running the scanner beyond standard hours routinely will have implications on tube replacement frequency, service support requirements and cost, and radiation protection issues. Figure 21. The stages of a CT scan REFERRAL Plan scan Justification Scan protocol selection Scan Schedule Patient to waiting area Prepare patient Primary and secondary reconstructions on scanner Transfer images to CT/MR workstation and/or PACS workstation Secondary Reconstructions/Post processing on workstation as required Transfer report to patient record Read images REPORT Transfer images To archive Staffing MSCT scanners may only be operated by appropriately trained staff [22], usually registered radiographers. They act under the supervision of ‘practitioners’ who, within the terms of the statutory instruments, are a registered medical practitioners (usually a radiologist) or other health professional who is entitled in accordance with the employer's procedures to take responsibility for an individual medical exposure. The operation of the scanning department will be supported by administrative staff who arrange appointments and carry out the patient reception duties, nurses and/or radiography departmental assistants (RDA), and porters for transfer of in-patients. Additional general support is provided by radiation protection and medical physics staff, from either within the trust or other organisations, who carry out periodic QA testing of the scanner. They will also advise on issues regarding optimisation of scanning protocols with respect to patient dose and image quality. These specialist staff should be trained to nationally recognised levels. Radiation protection advisors must hold a certificate of competence from a Health and Safety Executive (HSE) CEP08007: March 2009 Operational considerations 39 recognised assessing body [37], and be experienced in the relevant technologies. The local radiation protection supervisor (RPS) ensures that the ‘local rules’ for radiology practice are followed. (Local rules are mandatory instructions that are formulated to secure compliance with health and safety legislation). Utilising an appropriate mix of staff skills can reduce staff costs and improve patient workflow through the scanner. An example scheme is shown in Figure 22. Figure 22. Examples of allocation of specific roles to assist patient workflow Radiologist Referral – Justification – Scan protocol selection Schedule Patient - own transport (o/p) - or porter (i/p) Helper or Nurse Patient preparation - Cannulates, if appropriate - Reassures patient Patient to scanner room - Assists patient and radiographer Radiographer – Continues patient set up – Sets up scanner preassigned protocol – Scans – Image reformats etc Radiologist Views and Reports images Images automatically sent, as per protocol, to PACs or workstation Referral Under current legislation [22], where patients are referred for a scan, this must be justified by an entitled practitioner, and a suitable investigation prescribed. The choice of investigation, protocol, and scan parameters must comply with the ALARP (as low as reasonably practical) principle, to ensure that no unwarranted irradiation takes place. The ALARP principle is a standard tenet in radiation protection and health and safety legislation. CEP08007: March 2009 Operational considerations 40 Some departments have found delays at this stage of the process due to restrictions on the radiologists’ time. Systems that have been used to remove this pressure include batch processing of these referrals, and pre-selection of protocols, where a standard scan protocol is selected from a list at the time of justification. In addition, a specific member of staff may be allocated to screen the referrals to remove unwarranted referral requests according to well defined procedures. Pre-selection of protocols ensures there is no delay at the time of scanning. The protocol defines the anatomy to be scanned, and the required slice thicknesses, scan parameters, reconstruction procedures and post processing are all outlined. Systems to easily identify the scan protocol from the request form, such as protocol code numbers or tables with tick boxes, can simplify the process and minimise potential for error. Scheduling Improvements in scheduling can be obtained in a number of ways, according to the local mix of patients. Scheduling patients for particular types of examinations into fixed sessions can improve workflow, especially if specialist clinical support is required at the time of scanning to review the images. However, efficiency can clearly be compromised if there are not enough patients to fill a session for that particular examination type. If there are too many referrals and they cannot all be fitted into a particular session, some patients might have to wait up to a week until the next scheduled session. Some have found that scheduling patients who do not require contrast injections into sessions at the beginning or end of the day, when there is less likely to be a radiologist available, improves workflow. This ensures that there is no delay and scanning can take place with no delay. If two identical scanners are procured, then all scans can be booked onto one list and the first available scanner used. If the scanners differ, then systems need to be in place to determine which patients can only be scanned on a particular scanner. The availability of porters can affect the arrival time of in-patients. Some centres overcome this by having a specific porter, or porters, allocated to scanning or radiology. Another approach can be to balance the scheduling of the mix of inpatients and out-patients, so that outpatients can be scanned whilst waiting for late in-patient arrivals, or vice versa. Efficient procedures for checking the pregnancy status of patients will also ensure minimum effect on workflow. CEP08007: March 2009 Operational considerations 41 Patient preparation Improvements in patient throughput can be achieved by preparing the patient before transfer to the scanning room. Patient information and checks for contra-indications to the procedures, such as contrast intolerance, can be undertaken whilst the patient is in the waiting area. In some departments, cannulation is also performed prior to the patient entering the scanner room. This requires a suitable separate area, and trained staff, not necessarily a radiographer, such as an RDA or a nurse. Oral contrast administration preparation times can be shortened by changing the procedure for administration or adopting alternative strategies [34],[35]. Scan set-up Current scanners can obtain patient information from the modality worklists, which may come from the RIS, the PACS, or from a broker acting as an interface between the RIS and/or PACS, and the scanner. Pre-population of patient information fields on the scanner console during set-up can save operator time, and reduce the chance of error. Some scanners can also update the RIS or PACS as to the status of the scan, using performed procedure steps. Patients may need to be instructed about breath-hold and contrast injection during the scan. Systems such as visual breath-hold indicators and voice announcements can ensure that the patient complies with the scanning requirements. Modern systems offer a selection of language choices, and some systems allow the recording of additional announcements. With increased speed of scanning, the timing of the scan relative to contrast administration is important. Systems generally include a trigger system that will initiate the scan, based on a time delay or ‘bolus tracking’. Automated dose reduction systems are intended to optimise the patient exposure to ionising radiation whilst maintaining adequate image quality. These require extensive user training. Set-up, testing and optimisation of these systems require the support of a medical physicist. Image reconstruction It is generally thought to be good practice for scanner operators to check images before removing the patient from the scanner. This may take from a few seconds to a few minutes depending on the performance of the reconstruction computer. Systems that provide fast reconstruction and easy review of images at the console minimise delay, and help to increase throughput. To facilitate rapid verification of images, CEP08007: March 2009 Operational considerations 42 some scanner manufacturers provide preview image reconstruction at reduced image quality. Some centres have a ‘scan and send’ policy, for routine examinations, which does not require a radiologist to review the images prior to sending the patient away, reducing delays due to radiologist unavailability. For ease of reporting and specialist applications, there are a number of additional processing steps that the image data undergo, for example to reconstruct with different convolution algorithms, to reconstruct 3D views, thick or thin slab MIPS or MiniPS (maximum or minimum intensity projections) etc. Where these secondary reconstructions are set-up in the protocol, the need for user intervention in postprocessing activity may decrease. However, increasingly, the CT data set is regarded as a volume, and the 3D reconstructions, MIPS, MPR (multiplanar reformats), etc may be instantly available rather than secondary reconstructions with the thicker axial slices only reconstructed for image storage. The quality of the MPR, MIP and 3D reformatting from image slice data sets is best when reconstructed from thin slices. Many centres choose to store only the thicker slice data sets, to reduce data storage, however any subsequent reformatting from these data sets will result in reduced image quality, compared to thin slice data sources. This is an additional advantage to prescribing these reformats in the protocol, so that the thin slices are used while they are still available. Some systems can process the secondary reconstructions whilst the next scan is being set up, others may pause one or the other function depending on shared computing resources. The interdependence of scanning and reconstruction may affect throughput in departments where a large number of alternative reconstructions are requested routinely. The volume of acquired (raw) data is large, and often only stored on the scanner computer, where the data are typically overwritten cyclically. For many scanners the cycle time may only be a week or a few days, dependent upon the rate of scans, the amount of data acquired for each scan and the storage disc size. Once the raw data are overwritten, further formatting of images can only be carried out from stored slice data sets. Routing of images to stores, such as workstations and archives can also be preset for given protocols. This may be for the complete study, or for a specific series of images. CEP08007: March 2009 Operational considerations 43 Further processing Additional processing can be carried out on the scanner console, on the scanner workstation, or on the PACS workstation. Some functions will be available on all three systems, others will be limited to scanner console and workstation. For more specialist applications, such as cardiac analysis, vessel analysis, or automatic lung nodule scoring, software packages will only be available from the scanner workstation. Systems can also be purchased to allow processing of data on the workstation through remote access, and thin-client systems. The usability of the application software will affect the efficiency of workflow at this stage. Applications that use standard interfaces and inputs, are intuitive, and provide suitable prompts when required, may improve workflow initially or for rarely used applications. Some systems allow users to record macros or shortcuts to reduce the inputs required. Post-processing may be undertaken by a radiographer, technician or clinician. Suitable training must be undertaken for each application. In studies requiring post-processing or specialist analysis software, suitable worklist systems should be in place to maintain effective use of reporting radiologists’ time. If reporting from the workstation, then dictation, a voice recognition system, or another reporting system, must be available at, or adjacent to, the workstation. Specialist applications Specialist applications, due to their complexity, tend to slow down patient throughput. This can either be due to time in the scanner room during interventional procedures, or in additional preparation and processing time (eg for cardiac examinations). Interventional use CT systems can be used for real-time and interventional procedures, such as guided biopsies. These may also be called real-time CT, or CT fluoroscopy. Manufacturers supply additional configurations and accessories for interventional work. The necessity for these additions will depend on how the interventional work will be carried out. There are currently two approaches: in-room and out-of-room use. For in-room use the interventionalist is in the scanner room when the exposure takes place. A slave monitor in the scanner room displays a real time image, and the X-ray exposure and the couch motion can be controlled using a foot switch and a ‘floating table top’ control on the scanner couch. Even with appropriate lead apron and protective gloves (if needed), this will increase the radiation dose to the member of staff. CEP08007: March 2009 Operational considerations 44 In the out-of-room approach all staff vacate the room while the scan is taken. The position of, for example, the biopsy needle is checked from the image at the scanner console and the clinician re-enters the room to carry out any subsequent adjustment. This reduces staff dose, but increases the time taken to carry out the procedure. For either approach, there are common general concerns. Repeated imaging of the patient increases the dose burden. Systems should acquire only enough data to ‘refresh’ the image to the quality required for the procedure. The clearance between the patient and the inside of the gantry aperture should be sufficient to allow the clinician reasonable access to the relevant site. Moving the patient out of the gantry for adjustment of the biopsy needle can lead to misplacement and misregistration on images, and may lead to more imaging (and hence dose) than necessary. Cardiac procedures Cardiac examinations can be complex, and require specialist expertise to optimise scanning. The patient is generally given beta-blockers to stabilise the heart rate, although some manufacturers claim that their scanners are unaffected by irregular heart rates. The patient is wired to an ECG monitor that is interfaced to the scanner. This information is used to gate the acquired image data for subsequent reconstruction. Further processing of the images is generally carried out on the scanner workstation to release the scanner for subsequent patients. Information workflow Due to the large number of images generated by modern MSCT scanners, it is very important, on deciding to purchase a new scanner, to review the information workflow, and the location and use of CT scanner and PACS workstations. New approaches using remote thin client systems might also be investigated. The questions that need to be considered for optimising information workflow are: Where does the reporting takes place? What images are reported? What data are saved? Images can be sent from the scanner to the CT scanner workstation and/or transferred directly to the PACS store. On the CT workstation, complex processing can be undertaken prior to reporting. From the PACS store images can be displayed on a PACS diagnostic workstation for reporting (it may be also be possible to carry out simple processing), or on a lower specification review station for review. Images from the CT scanner workstation can also be displayed and manipulated using a computer at a remote location using a thin client system. These options are shown in Figure 23 CEP08007: March 2009 Operational considerations 45 Figure 23. Information and image flow Efficient workflow requires optimising how the images are viewed on the equipment available. This requires some knowledge of the capabilities of the network and computers that are used. Currently an MSCT data set can comprise 1000 to 2000 images per patient, and networks and computers vary in their capability to handle this volume of data. Thin slice imaging is currently the normal approach for MSCT scanning, and images may be sent to the PACS or scanner workstation as the complete set of thin slices, or, as a smaller set of thicker slices and multi-planar reformats. The number of images also has an effect on the data that will be stored as part of the permanent patient record within the hospital systems. Guidance on the retention of radiological patient data has been published by the Royal College of Radiologists [38]. (See also Data management below). There are also specific regulatory requirements for recording patient dose data [22]. This can either be as the computed tomography dose index (CTDI) and dose-length product (DLP) values, or with enough scan parameters to enable this information to be calculated at a later date. CEP08007: March 2009 Operational considerations 46 CT scanner workstation The CT scanner workstation is used for complex processing, and the full range of three dimensional reconstructions (such as volume rendering, slab maximum and minimum projections, curved planar reformatting, surface rendering), as well as for the specialist software applications such as those for cardiac analysis and virtual endoscopy. It may be possible to share a manufacturer workstation between two modalities, such as CT and MR scanners. This will help offset the expense of the application packages and licences. However, this will depend on the applications and processing required, and the working patterns within the department. PACS workstation The PACS diagnostic workstation is primarily used for reporting, however some reconstruction functionality (eg multi-planar reformat, MIP, some 3D reconstruction) may be available. It is worth noting that these reformats will not necessarily use identical algorithms to those on the CT scanner workstation, and there may be a difference in quality. Remote access – thin client systems Images from the workstation can also be displayed on a computer at another location linked through the hospital network using a ‘thin client’ system. These systems are available from all manufacturers through the purchase of single or multiple user licences. These software packages enable a remote PC to log-on to the scanner workstation, using either a dedicated client application, or one based on commonly available client application interfaces such as web browsers. The user can then perform both simple and complex workstation functions remotely, The advantage of thin client systems is that they allow viewing and processing functionality from less powerful computers by carrying out the processing on the central server. However the network demands are increased. The latest systems are designed to provide a common interface to the user for all applications, regardless of modality. This can reduce the training and application support requirements. Generally, licences are required for each client computer that connects to the workstations remotely. The exception is viewers with no processing functionality. It should be clearly established what level of review and processing functionality is required at each remote client, based on clinical need and workflow designs. CEP08007: March 2009 Operational considerations 45 Figure 23. Information and image flow Efficient workflow requires optimising how the images are viewed on the equipment available. This requires some knowledge of the capabilities of the network and computers that are used. Currently an MSCT data set can comprise 1000 to 2000 images per patient, and networks and computers vary in their capability to handle this volume of data. Thin slice imaging is currently the normal approach for MSCT scanning, and images may be sent to the PACS or scanner workstation as the complete set of thin slices, or, as a smaller set of thicker slices and multi-planar reformats. The number of images also has an effect on the data that will be stored as part of the permanent patient record within the hospital systems. Guidance on the retention of radiological patient data has been published by the Royal College of Radiologists [38]. (See also Data management below). There are also specific regulatory requirements for recording patient dose data [22]. This can either be as the computed tomography dose index (CTDI) and dose-length product (DLP) values, or with enough scan parameters to enable this information to be calculated at a later date. CEP08007: March 2009 Operational considerations 48 larger for more specialist applications where there are more reconstructions or reformats, and 4 times larger for images of 1024 x 1024. As an alternative to long-term storage of all data, departments may choose to store the data acquired with narrow slices only for a short period of time, whilst it is required for processing and reporting. This may need to be revised in line with best practice since updated guidance on record retention [38],[40]. Many departments continue to back up data at the scanner, in which case the scanner must have a back-up facility and secure storage for a large number of discs. It should be noted however that the reliability of central storage now generally renders this practice redundant. Systems are now available that burn data discs for dispatch to external clinics or for medico-legal use. Systems that produce standard formats (such as DICOM part 10 [41]) should be chosen. Automatic labelling of the disc with unique, human-readable data should be preferred. Department of Health policy now requires password protected encryption of the information on removable media. Interoperability Introduction This section relates to how the CT scanner system interacts with other systems in the department and in the hospital. These may be other imaging modalities, specialist systems, or patient and image data management systems (such as PACS, RIS, Hospital Information System (HIS), etc). Systems integration Many systems have the capability to integrate resources. Most modern scanners have functionality on the console that was previously only available on specialist workstations. Standardised exchange of image data between scanner, workstation, and storage systems is achieved by compliance with DICOM standards [42]. Patient information, including the final report, is managed by HL7 systems [43]. Overarching frameworks, such as IHE [44], provide a background that encourages suitable interoperability between systems. Manufacturers will supply DICOM conformance and IHE integration statements on request. Specialist knowledge is required to ensure that the required data exchanges can be achieved by the systems under consideration and those already existing in the hospital [45]. CEP08007: March 2009 Operational considerations 49 There are two published standards for DICOM objects that store CT image data [46]. The standard applicable to the scanner output data might therefore differ from that applicable to the input data for other systems within the workflow. Responsibilities for interfacing the scanner with the PACS or other systems must be clearly defined. This may involve the local PACS and RIS managers and suppliers of the related systems. Although systems may have the capability to carry out certain exchange functions, these may not be enabled or configured in the basic package offering. Activation and configuration requirements should be included in the tender. Local ICT departments should always be involved as network traffic, data storage and security will need to be considered. Influence on existing modalities Most CT scans do not involve direct interoperability or integration with other imaging modalities. Exceptions such as PET-CT and SPECT-CT are beyond the scope of this buyers’ guide. Where such ‘fused imaging’ systems are under consideration, specialist advice should be sought from professional bodies such as the Institute of Physics and Engineering in Medicine (IPEM) and the British Nuclear Medicine Society (BNMS). In departments with more than one CT scanner, issues may arise due to specification and capability differences. Many general scans can be carried out on any scanner, but some have specific technical requirements. The flexibility of having multiple scanners all capable of carrying out any required scan should be balanced against the risk of over-specification. The additional expense incurred may result in higher patient throughput depending on the workload mix. Options for sharing resources such as workstations and staff may also be a factor in choosing a scanner. There might be advantages to selecting an additional scanner from among the models offered by the manufacturer of the existing one, due to ease of transfer of skills between scanners, and contractual efficiencies. These advantages will apply to a lesser extent when all existing scanners are to be replaced. Specialist systems In some circumstances, data from the CT scan may be used in other specialist systems. Scanners that are to be used with radiotherapy treatment planning systems will have special requirements with respect to accuracy of CT number values and patient positioning. These scanners will also have additional requirements for accessories, acceptance and quality control testing. CEP08007: March 2009 Operational considerations 50 Surgeons may use CT data sets to visualise and plan operations. Orthopaedic planning, stent fabrication, and neuro-navigation systems may be used. These may require specific data sets from the scanner and place additional constraints on image quality. Systems exist where the CT data are used to plan the settings for subsequent conventional angiography. This may reduce the time taken to plan and optimise the angiographic procedure. In each case, it must be established that the data set transferred from the scanner is compliant with the requirements of the destination system. Standard image transfer facilities might be inadequate in this respect. It should also be established whether the destination system accepts data transfer across a network, or requires transfer on physical media. Information security It is the responsibility of all health care professionals to ensure that personally identifiable patient or staff data are kept confidential and secure. Information governance (IG) is about how sensitive information is produced, used, archived and destroyed. IG should be regarded as part of clinical governance processes. Local IG principles must be kept in mind when considering how patient data are to be managed during the CT scanning processes, and thereafter. Where data may be transferred outside of the trust, approved systems should be used. If systems are used to transfer data to physical media (CD, DVD, MOD, USB stick) there will be a requirement to encrypt the data. Preference may be given to systems that provide this facility automatically. If data are to be used for non-clinical purposes, such as teaching and research, there may be a need to anonymise the data – that is remove all patient identification from the file. Systems exist that remove generic information from standard file formats, such as DICOM header tags. It should be established that use of such systems complies with national [47] and local guidance. Certain files may contain patient data in so-called private tags. If this is the case, it should be determined how these are handled by existing anonymising processes. Access to patient data is normally based on a ‘legitimate relationship’ to the data. Generally this limits access to those who need to know for clinical management purposes. Certain levels of service contract provide for remote fault diagnosis, which requires the service organisation to have modem access to the X-ray system. As it is now common for imaging systems to be connected to HIS/RIS or PACS, this creates the potential for unauthorisched access to patient information via the scanner or CEP08007: March 2009 Operational considerations 51 workstation. Security must therefore be considered when setting up facilities for remote system support and fault diagnosis. Any use of, or connection to data on the scanner must be in full compliance with national and local policy, such as the NHS Code of Practice [47] Local network security boards, IT departments, and NHS Connecting for Health [48] can advise on the external connection to the scanner. Approval for cases where patient identifiable information may be exposed must be obtained from the local data protection officer (normally the Caldicott guardian). Safety issues As with most clinical investigations, there are safety issues related to the handling of patients, radiation, infection, use of injections, use of medical gases. These should always be considered in relation to existing local guidance. Particular issues related to CT scanning that should be considered are highlighted here. Ionising radiation As with any imaging modality involving the use of X-rays, the hazards of ionising radiation must be considered under IRR 99 [21], and IR(ME)R 2000 [22]. IRR is mainly concerned with safety of equipment and staff, whereas IR(ME)R focuses on the protection of the patient. There will need to be a radiation protection advisor (RPA), appointed under IRR 99 [21] with responsibility, among other things, for scanner equipment safety and the protection of staff and the public. The radiation protection advisor (RPA) should be involved throughout the purchase project and thereafter to ensure continued compliance. A medical physics expert (MPE) is also required, appointed under IR(ME)R 2000, to give advice on matters relating to radiation protection concerning medical exposures, such as patient dosimetry, quality assurance and optimisation of protocols. There are legal constraints on dose exposures to the public and staff; these must be enforced through local rules and routine surveys. There are requirements to maintain patient dose records, and carry out routine dose audits. Staff must also be monitored. Systems must be in place to ensure compliance, and adherence to current best practice. It is the duty of the hospital board to ensure compliance, with advice taken from the RPA. Due to the inherent risk involved with the use of ionising radiation, ‘justification’ of a medical exposure is required by law [22] and is one of the main tenets of radiation protection. Any CT procedure must be justified in terms of potential clinical benefit. CEP08007: March 2009 Operational considerations 52 The RCR produce guidelines as to where CT is the preferred investigative technique and where it is not justified [49]. IR(ME)R 2000 requires that the dose given to a patient is recorded either directly (eg volume CT dose index (CTDIvol) and dose length product (DLP)), or indirectly from scan parameters, (allowing the dose to be calculated retrospectively). Average doses to a group of patients for common examinations should be compared periodically to the associated diagnostic reference levels (DRLs) [17],[32]. CT is a high radiation dose procedure [16]–[20]. The specialist applications of fluoroscopy, perfusion and cardiac scanning give particularly high dose levels, and protocols for these applications warrant specialist attention, preferably in consultation with the local medical physics department. Training can help in the optimisation of these specialist scanning regimes. Automated dose reduction systems are intended to minimise patient exposure to ionising radiation, whilst maintaining adequate image quality. These require extensive user training. Set-up, testing and optimisation of these systems require the support of a medical physicist. A robust system for patient identification is critical in ensuring that the patient is not scanned in error, or with the incorrect protocol. Where patients have been exposed to ionising radiation to a degree ‘much greater than intended’, this must be notified to the Healthcare Commission, to whom the responsibility for enforcing IR(ME)R was transferred, by the Department of Health, in November 2006 [50],[51]. Where radiation exposures are much greater than intended owing to equipment failure, there is a need to notify the Health and Safety Executive (HSE) [104] under IRR 99 [21]. Infection control Local infection control teams will need to be consulted regarding the scanner suite facilities. Key issues include requirements for flooring and lack of ‘trap’ areas around the scanners, and positioning of sinks and other hand cleaning stations in the suite. Cleaning of the scanner is routine. Most manufacturers will supply a ’slicker‘ couch cover as standard. Manufacturers are able to provide guidance on suitable cleaning methods. Checks should be made whether local cleansing products will affect the scanner surfaces. If replacing a scanner, the existing scanner room should undergo deep cleaning as part of the pre-installation phase. CEP08007: March 2009 Economic considerations 53 Cost effectiveness Evidence of cost effectiveness is useful for the preparation of the business case. Cost effectiveness may be enhanced by negotiating lower prices, controlling running costs, optimising operational procedures, maximising the impact of the CT scanning service, and reducing overall clinical management costs. Few economic studies have been undertaken regarding CT imaging [52]. Most compare various pathways of patient management where CT scans are involved (see [53] for examples). The additional cost of undertaking a CT scan is considered to be outweighed by the improvement in effective management of the disease. For example, a US study identified that CT-based management strategies for head injury cases were not only clinically superior to those without CT, but reduction in subsequent treatment costs made these strategies cost effective [54]. Immediate CT scanning of patients presenting with suspected stroke has also been identified as a cost-effective approach to differentiation between cerebral infarction, cerebral haemorrhage, and stroke mimics. Although this was the highest cost strategy considered, improvement in clinical management decisions lead to a reduction in overall costs [55]. Routine CT scanning is not a cost effective follow up in Hodgkin’s disease [56]. In 2007, the Committee on Medical Aspects of Radiation in the Environment (COMARE) of the Health Protection Agency (HPA) issued guidance on CT scanning of asymptomatic individuals [12]. Scanning in these circumstances is not recommended for most types of examinations, although under strict conditions certain allowances are made for coronary calcium scoring and colonography. In addition, an Institute for Clinical Systems Improvement (ICIS) study, in 2003, found that no evidence exists to evaluate the effectiveness of whole-body CT as a screening test for patients with no symptoms or a family history suggesting disease [57]. A 2006 Health Technology Assessment report on lung cancer screening [58] found no evidence to support clinical effectiveness, and no evidence of costeffectiveness. Costs and remuneration Indicative scan costs The average cost of a CT scan, compared to other diagnostic imaging procedures carried out by NHS trust radiology services, is reflected in the average unit cost tariffs given in Table 5. Note that these examples have been shown for each imaging modality, although neither the diagnostic aim nor value may be directly comparable. The figures show that: CEP08007: March 2009 Economic considerations 54 • CT costs more than plain X-ray or ultrasound investigations, • CT costs are less than those of nuclear medicine procedures • CT costs are comparable with those of MR and fluoroscopy procedures. Although dual-energy CT scanning is used in some research centres, it is not yet considered an alternative for DEXA scanning for bone density assessments. Table 5. Average unit cost tariffs for different diagnostic imaging modalities [59] Diagnostic imaging procedure Average unit cost tariff (£) MR 169 CT 131 DEXA 49 Contrast fluoroscopy 159 Ultrasound scan 69 Nuclear medicine procedure 228 Plain film (or CR or DR) (one area) 29 * Note: * Based on previous reference costs [66] with a 2.5% uplift Payment by results The NHS is moving towards the payment by results system, (PbR) [60] with reimbursement based on the costs of treatment strategies as categorised into healthcare resource groups (HRGs) [61], sets of patients requiring broadly similar management. Each of these is allocated a HRG code, against which a national tariff has been set. Since the publication of HRG v4, radiology procedures, such as CT scans, are treated as an ‘unbundled component’ [59], that is, an additional cost item. Hence, procedures involving CT scanning will have additional HRG codes, the core HRG code for the patient treatment, and relevant radiology HRG code. Using a unit of tariff of £144 (based on the indicative average unit tariff for CT, given above in Table 5, and including the addition of a typical market forces factor (MFF) of 10%), a typical hospital, with two MSCT scanners carrying out 14,400 CT based investigations, will generate payments of just in excess of £2m per annum. CEP08007: March 2009 Economic considerations 55 Investigation coding CT investigations will initially be assigned a code, such as OPCS-4 (Office of Population Censuses and Survey Classification of Surgical Operations and Procedures, 4th revision)[63] or SNOMED CT (Systematised Nomenclature of Medicine Clinical Terms) [64]. Currently there is no prescribed mapping from these codes to the relevant payment codes (HRG v4). The range of CT procedures will attract different levels of payment, which vary from £105 to £223 (Table 6), and therefore all CT investigations must be properly coded to ensure that the correct tariff payment is collected [65]. Table 6. Indicative PbR tariff for CT diagnostics, 2008-09 Radiology HRG banding Sample unit cost tariff (£) CT, one area, no contrast 105 CT, one area, post contrast only 131 CT, one area, pre and post contrast only 152 CT, 2 or 3 areas, no contrast 132 CT, 2 areas with contrast 164 CT, 3 areas with contrast 176 CT, more than 3 areas 223 For example [62], a CT scan of the head may be classed as: • CT one area, pre and post contrast • CT one area, post contrast only • CT one area, no contrast. Miscoding this investigation could lead to a 30% underpayment of tariff. Implementation of RIS systems throughout NHS as part of the NPfIT programme has improved access to electronic data regarding the scans undertaken. Where a direct link between the departmental RIS and the hospital PACS exists, automatic allocation of coding should ensure the correct payment is claimed. Where there is no such link, proper systems must be in place to ensure clinical coders have sufficient information to correctly allocate the base and subsidiary codes that will ensure the correct HRG allocation. Whether the allocation is automatic or manual, the mapping exercise from local procedure codes to HRG codes must be undertaken with care. When setting up the scanner, it should be ensured that the correct scan can be easily CEP08007: March 2009 Economic considerations 56 chosen for the investigation booked on the RIS. Any changes between the requested scan during justification and the selected scan protocol should be indicted in the RIS data. Cost model Most trusts will be undertaking an exercise to quantify their own standard costs for diagnostic procedures. These should address radiological investigations, including all CT scans. The local project officers should be consulted for the latest figures for use in economic planning. The following cost model is given as a guide for use in initial estimates. The costs in the discussion below are reasonable estimates based on discussion with users and service managers. They are given for indicative purposes only. Example annual costs, from this discussion, are summarised in Table 7. Each particular procurement and installation project will require its own cost analysis based on local data (see Whole-life costs). Table 7. Example annual direct operating costs for CT scanner Cost per annum (£) Relative contribution to total cost Relative contribution to non-staff costs Capital costs 106,000 12% 24% Service & support 70,000 8% 16% Consumables 175,000 20% 39% Other 97,500 11% 22% Staff 415,000 48% n/a TOTAL 863,500 Cost item A typical MSCT scanner system will cost around £500k, including installation and initial training. Basic works to refurbish an existing scanner room will cost around £30k. There may be a cost of up to £75k for additional radiation shielding and increased power supply, which is often required for an upgraded scanner. This latter element has been excluded from this model. A new scanner room build will have a higher cost. Assuming that the capital costs are allocated over a 5 year period, this gives an equivalent annual cost of £106k. Capital asset depreciation is not considered. CEP08007: March 2009 Economic considerations 57 Routine maintenance and servicing of radiological equipment typically costs around £50k per annum. A replacement X-ray tube costs of the order of £70k. The frequency of replacement will vary with model and use. Newer tubes are likely to have a reduced replacement frequency compared to older scanners. A spare could be bought at the time of scanner purchase or costs could be budgeted over a specified period. Allowing £20k per annum for the replacement x-ray tube would not be unreasonable. A total of £70k is allowed for service and support costs. It is assumed that all the workstations and applications software required is included in the purchase price for the CT scanner system. An additional workstation may add an amount around £40k to the capital costs, and £5k to the annual support costs. Consumable costs are mainly related to the contrast use. As an initial assumption, just over 2/3 of scans will be contrast enhanced. The cost may be £20 per use depending on the amount, mixture, syringe costs and such. Other consumables are assumed to be of the order of £10 per study. For this model, a scanner with a mixed workload is assumed, achieving a throughput of 25 patients in an 8 hour day, 250 scanning days per year. Assuming around 15% additional scans occur ‘out of hours’, this gives an annual volume of approximately 7,500 studies, with 5,000 contrast enhanced. Contrast costs will be £100k per annum, and £75k for other consumables. Additional costs include those related to data storage, and other general use items. PACS, or similar, storage is estimated as £8 per scan, and another £5 per scan is allowed for miscellaneous direct costs. The model includes an annual cost of £97.5k for these items. Total staff costs are included in this costing model, and are assumed to cover salaries and other related costs. If the scanner is a replacement scanner, then the staff costs should be modelled on any changes to existing staffing levels. The staffing is based on: • • • • • £180k for 1.5 full time equivalent (FTE) consultant radiologists £75k for one junior clinician (SPR or equivalent) £80k for two radiographers £20k for 1/3 FTE of other technical staff £60k for clerical and other support staff. Factors such as extra session payments and unsociable hours, plus any retention premiums are assumed to be covered within these costs. Some specialist technical skills, such as an RPA, may be bought in as external services, but are included in the technical staff salary costs for this model. CEP08007: March 2009 Economic considerations 58 Ongoing and professional training is neglected as part of the overall departmental budget. Specific application training and such is assumed to be covered within the support contract costs. Most trusts will require a proportion of the overall operating costs of the hospital to be included in the costs of a department. For this model this is assumed to include any power costs for the department as a whole. Allowing 20 percent of the total cost for this gives an indicative annual cost to the department of around £1m per annum for the scanner. The highest single contribution to the above model is salary related. Any features of a new scanner that will improve the efficiency of staff use, such as improved workstation tools, simple scan set-up and management, has the potential to reduce the cost per scan. Also changes in overall working practice and workflow within the department will affect this figure. However, if the scanner is used for increasingly complex procedures, then the staffing costs may increase. Departments that operate more than one scanner will be able to optimise staff expenditure by using common resources. Two scanners are likely to have less than double the staff costs of one scanner. The direct revenue costs of staffing, reporting, and data storage are very dependant on local working practices. For a scanner replacement, there may not be a major variation from current staffing levels, but there could be an increase in reporting and data processing tasks, which could lead to a slight increase in staffing revenue costs. This will be highly dependant on the investigations undertaken, the application software chosen, the workflow patterns, and numerous other local factors. After staffing, the next highest contribution is from consumables. In this model, 22% of the non-staff expenditure is for the use of contrast. Techniques available with MSCT scanner may allow for more efficient use of contrast, however more complex investigations may increase this cost item. The annual support costs (service and tube replacement) are approximately 1/8 of the capital costs at the first year. Over a typical 7 year operating life, and factoring in a uplift of 6% per annum, this will then represent a life cost 10% greater than the initial equipment purchase, installation and building costs of the scanner. Fixing the price of the service contract for 5 years gives a potential saving of 8% over the operating life. Cost control As well as negotiating on the cost of the main scanner and equipment, there is some benefit from including additional items at the point of tender. This can fix on-going CEP08007: March 2009 Economic considerations 59 costs for a set period, facilitating budgeting and possibly generating cost savings. The following items should be considered for inclusion in the tender: • • • • • • • • • • • service costs for a specified period fixed price consumables for a specified period additional training for radiologists and radiographers additional workstations and software planned upgrades to applications (to match future introduction of new clinical services) and workstations, plus associated support and training future replacement of LCD monitors ‘with tube’ service contracts or replacement tube costs data integration services to ensure connectivity of the scanner and workstation to the RIS, PACS and other local data systems additional storage – for future expansion of local archive storage, whether on-line or optical disc service continuity (eg provision of a mobile unit whilst works are undertaken) phantoms, test objects and other QC testing equipment. Whole-life costs In order to make the most effective procurement decision, whole life costs should be considered for each purchase option. These should account for capital costs, and revenue costs over the expected life of the scanner. There are a number of areas where the cost elements are often neglected. Some of these are identified below. Costs related to the disposal of the equipment should also be considered. Key items that typically contribute to whole life costs are listed in Table 8. Local costs for these items should be determined by the purchase team as part of the purchasing activity. CEP08007: March 2009 Economic considerations 60 Table 8. Contributors to whole-life costs Life-cycle phase Specific contributors Purchase Equipment purchase; scanner, ancillary equipment, accessories, workstations, application software. Capital item depreciation. Support equipment such as an emergency trolley, power contrast injectors, ECG monitor, etc. Installation Removing previous equipment and disposal. Preparing the area, including deep cleaning, estates services (power, lighting, cooling equipment, patient and staff areas, telephones and data points, office equipment). Provision of interim scanning services. Connection to systems such as RIS and PACS. Initial staff training may be seen as an installation/set up cost. Commissioning Acceptance testing. Formal radiation safety test report. Electrical and mechanical safety testing. Operation Radiology staff: radiographers, radiologists, RDAs On-call and out of hours cover. On-going staff training. Support staff; administration, portering. Routine equipment testing; QC test, RP surveys. Consumables: contrast agent, disposables, gases. Power and services. Service contracts and maintenance costs. Maintenance of associated equipment (eg power contrast injectors). Film and digital data media. Cost of network/PACS support for image and data storage. End of life Removal: decontamination and disposal. Data migration. Hidden costs Hidden costs might sometimes be overlooked, resulting in unexpected additional expenditure to complete the project. The following list comprises items known to have been overlooked in previous CT scanner installations. Reviewing these may help purchasers to avoid similar errors. • Power supply – to the standards required by the new scanner. Existing room and department supplies may not always be sufficient • power cables – new scanners may have specialist requirements for the power connections • building works – especially provision of sufficient shielding and load bearing CEP08007: March 2009 Economic considerations 61 • systems integration – ensuring the transfer of data from the scanner or workstation to the PACS system • networking – additional data cables and network equipment to ensure efficient connection of systems • data storage – potential for huge increases in networked and media requirements • increased portering – more patients means more beds to move • extra patient preparation – more patients may require an increase in waiting room size and changing facilities. Additional rooms and staff may be required for pre-scan cannulation, for example • extra reporting requirements – increase in the number of investigations may require an increase in the number of radiologists (or specialist radiographers) reporting and hence increase in both staffing levels and reporting facilities • desktop computer upgrades – remote access and thin client systems allow ease of access to the data and some processing functionality, but not all existing office PCs will meet the basic requirements for reasonable performance. Cost of disposal Disposal costs will apply to any equipment being disposed of as part of the upgrade to the imaging facilities. This may include decontamination of the existing scanner, accessories and the scanner room. Disposal costs can also be considered for the new equipment being purchased. Manufacturers will commonly offer to defer such costs until end-of-life. This way the purchaser can benefit from any reduction in the disposal costs during that time. It may be prudent to include removal of all existing equipment as part of the tendering process in order to ring-fence related costs. Prospective purchasers should refer to The Waste Electrical and Electronic Equipment Regulations 2006 [67],[68] , and related guidance [27], which will have an impact on the purchase and disposal cost of equipment. CEP08007: March 2009 Purchasing 62 Introduction A scanner may be purchased, leased, or operated as a managed service, in which a supplier provides the scanner and plays a role in managing the service. Due to the value of the project to procure a CT scanner, hospitals may employ the services of a capital projects specialist. Involvement of all relevant departments at an early stage is strongly recommended to ensure success. NHS PASA policy identifies the legal framework within which all NHS purchasing should be undertaken, and key policies within this area that those involved must observe. The overarching procurement policy [69] states: “All procurement activity in or on behalf of the NHS must be conducted in accordance with public procurement regulations and should be based on achieving value for money. NHS procurement should also contribute to the delivery of wider Government policies and priorities wherever possible.” At all stages of the procurement process, the purchaser must be fair, and seen to be fair, as any decision made can be challenged by any of the manufacturers who are not awarded the contract. Guidance is to be found in the National Framework of Standards for Best Practice Procurement in the NHS [70]. Two elements of good practice are to [71]: • involve key stakeholders throughout the process • seek value for money, not just lowest price. Due to the complexity of the technology, the high equipment value, and rarity of the purchase, procurement teams are encouraged to seek advice from experienced users and support organisations. This is particularly important when considering technical specifications and performance. Advice may be obtained from NHS PASA, especially the Centre for Evidence-based Purchasing (CEP), and professional bodies such as the Royal College of Radiologist (RCR), British Institute of Radiology (BIR), Society & College of Radiographers (SCoR),and Institute of Physics and Engineering in Medicine (IPEM). Purchasing procedures The Trust Operational Purchasing Procedures Manual provides details of the procurement process [72]. CEP08007: March 2009 Purchasing 63 European Union procurement rules apply to public bodies, including the NHS. The purpose of these rules is to open up the public procurement market and ensure the free movement of goods and services within the EU. In the majority of cases, a competition is required and decisions should be based on best value. The EU procurement rules apply to contracts worth more than £90,319, net of VAT (from 1st January 2008) [73]. Further details of the process are detailed in appendix 2. Detailed advice and support on procurement is available from local procurement departments, and from the resources of the NHS PASA website. The CT purchase process This section covers the basics of the CT purchase process. A CT purchasing project requires the interchange of a large amount of information. In most cases, local purchasing procedures will exist. The local procurement officer should always be consulted to ensure that they are followed. The sequence of events may vary depending on local circumstances, but that shown in Figure 24 is typical of such projects, these stages of the purchasing process are also shown in figure 25 and expanded on in the text. Figure 24. Schematic diagram of information flow during purchasing process Medical director Capital Equipment Board Finance Estates Medical physics 1. Request 2. Award of money Radiologists Radiographers Radiology business manager Medical physics Purchasing Decision Committee CEP08007: March 2009 – – Supplies Trust supplies officer, or Collaborative procurement hub, or nd al a c i – NHS Supply Chain n io n cli al, cificat n o ti e era al sp Op ic 3. techn lies 4. OJEU advert, rep r 6. Formal e Operational d n tender l te ) specification a orm ces replies & 7. F (& pri prices 5. Informal communication Site visits CT scanner vendors Purchasing 64 Figure 25. Schematic diagram of the stages in the purchase process of a CT scanner INITIAL TEAM: BUSINESS CASE PROCUREMENT ROUTE OPTIONS DECISION ON PROCUREMENT ROUTE; AWARD OF FINANCE SCANNER SPECIFICATION: CLINICAL, TECHNICAL & OPERATIONAL NHS SUPPLY CHAIN PROCESS OJEU ADVERT: INVITATIONS TO EQUIPMENT EVALUATION PROCESS, SITE VISITS EQUIPMENT EVALUATION PROCESS, SITE VISITS DECISION PROCESS RETURN & REVIEW OF TENDERS AWARD OF CONTRACT AWARD OF CONTRACT CEP08007: March 2009 Purchasing 65 Preparing a business case A business case must be approved before any procurement exercise is initiated. Further guidance on preparing business cases is available from the Office of Government Commerce [75] and RCR [76]. Illustrative examples are available on the NHS PASA web site [77]. Brief guidance is provided in appendix 4. The full business case should identify the current and future clinical practices that will be supported by the CT scanner purchase, and in this it is valuable to have the direct support of clinicians whose clinical services use CT. Involvement at a high clinical and operational management level is advised, as this project will have a large capital investment and will affect a wide variety of the services operated by the trust. Procurement route options There are a number of different ways in which a CT scanner service within a trust can be provided. These are largely dependent on financial and strategic considerations at a trust level, or higher. In each case, the provision of the service can be organised by the trust directly, or in partnership with a commercial supplier. They include: • purchased CT scanner • leased CT scanner • managed equipment service. If the decision is to purchase or lease the scanner, there are a number of different routes that may be taken. These are through: • • • • the trust’s procurement department collaborative procurement hubs (where applicable) DH initiatives (eg the recent capital investment programme for CT scanners) NHS Supply Chain. NHS Supply Chain [78] manages a framework agreement to facilitate the ordering of diagnostic imaging systems, which removes the requirement for individual trusts to undertake a tendering exercise. This framework is non-mandatory and organisations retain the option of using local purchasing arrangements. National frameworks from NHS PASA are in place for operating leases to help the NHS procure those more cost effectively (see appendix 2). Decision of procurement route, award of finance The business case will be submitted to the trust capital equipment board (or equivalent), or other processes followed depending on the mode of procurement. CEP08007: March 2009 Purchasing 66 Once the procurement route and finance available has been decided and agreed, the planning of the project can commence. Project planning Any purchase of this nature will require a team to be set up to manage the various aspects of the procurement project. For a CT scanner purchase, the team will typically consist of: • • • • • • radiology services manager radiologists radiographers / operators procurement specialist medical physics and / or radiation protection department estates and works. The purchase may be a ‘turnkey’ project, whereby the scanner supplier also supplies the required building work, or an ‘equipment only’ purchase. However, regardless of the type of project, the team will require the services of a project manager, usually a member of the estates department, to manage the overall installation of the equipment. The team will also need to co-opt other members with specialist knowledge, such as IT for the networking elements, a radiation protection advisor, and patient safety / infection control staff. The team will set the specification for the scanner, attend site visits and evaluate tenders. Not all members will be required for all activities. Timescales A CT procurement exercise can take up to 12 months to complete. This needs to be taken into account in the planning stages. The length of the exercise depends on the chosen route and associated procedures. Further information on this is available from the Department of Health [79]. It is common for CT scanner tenders to be placed in the latter months of the financial year, causing a bottleneck for manufacturers. Every effort should be made to avoid the busy period; liaison with sales representatives will help to manage this. Scanner specification ` Once the clinical services have been identified in the business case, then the operational requirements of the system can be specified. The statement of operational requirements can be in the form of an ‘output based specification’ (OBS), possibly backed up with a technical specification, or as a ‘detailed statement of need’ (DSoN). CEP08007: March 2009 Purchasing 67 The manufacturers will provide their tender responses based on the information supplied in this document, which should identify what the users want to achieve. This will allow fair and open competition between suppliers. Requests for features which are supplier-specific are not permitted. Very specific technical parameters which cannot be supported by operational requirements should not be included. An approach to drawing up the operational requirements is provided in appendix 5 together with an example statement of operational requirements. The use of standard specification questionnaires, such as that provided by ImPACT [80], for technical aspects of the scanner is strongly encouraged. Scanner companies have prepared responses in a standard format that allows comparison between suppliers. This practice was originally established as part of the Capital Investment Programme (CIP) [81], but since then, manufacturers have reported wide variations in the questionnaires used, which has hindered swift response on their part. If necessary, additional site-specific questions may be appended to the questionnaire. The replies to this questionnaire can be used by technical specialists to confirm claims made by the manufacturers about equipment performance. They may also be used as a basis for acceptance testing. Standard core specifications, with options, are offered by NHS Supply chain for all available CT systems. For the purpose of scanner evaluation, a performance specification should be derived from local operational requirements and agreed by the procurement team or selection panel. This will form the basis for assessing the adequacy of technical specifications provided in the tender replies and responses to the technical specification questionnaire. Purchasers can refer to the summary specification tables in the Market review chapter in this buyers’ guide. Full tables can be found in the appropriate Comparative Specification report [84]-[89]. Also available are qualified evaluations (eg [90]), the ImPACT online specification comparison tool ‘CTSpec’ [91], or information available from organisations such as ECRI [90] or Sg2 [93]. Identifying potential suppliers Although there are currently only four UK suppliers of CT full body scanners, a prequalification questionnaire may be employed as an initial screen to exclude unsuitable suppliers. In most cases, the standard NHS PASA pre-purchase questionnaire (PPQ) [82] is sufficient to ensure that all scanners meet current regulatory requirements. Associated purchases As well as the main CT scanner system and its accessories, the procurement project should address other related purchase needs. Ensuring that as many elements as possible are included in the initial tender can minimise issues arising later, and may reduce costs. CEP08007: March 2009 Purchasing 68 Elements that should be considered for inclusion in the tender are: • • • • • • • • • • • service and maintenance training application specialist support spare parts – including replacement tubes fixed consumable costs planned upgrades service continuity during installation building works – including additional shielding network infrastructure upgrade data storage data conversion. If these are not included in a single tender, then they should be managed as closely as the main scanner purchase, as failure to procure proper services or accessories will delay the start of clinical use of the scanner. Procurement process This stage will either be an engagement with the NHS Supply Chain to access the NHS framework agreement, or issuing an invitation to tender through the Europe tendering process by the placement of an advert in the Official Journal of the European Union (OJEU). Equipment evaluation The main sources of information that should be used to evaluate the equipment are the tender responses and site visits. Additionally, information on specific questions may be obtained informally from the manufacturer, other users, and professional bodies and support agencies such as RCR, BIR, IPEM and SCoR. Site visits Site visits may be arranged, even during the period that the invitation to tender is issued, under the formal approval of the procurement department. Site visits should be co-ordinated by the procurement team, making sure that all interested parties get a chance to visit the site. This should include clinical and technical specialists; appendix 6 suggests those who should be included on a site visit. The manufacturer usually has designated sites for visits, but as far as possible the site visited should have a similar service profile to the one being set up. A check list of questions to be addressed should be drawn up to maximise the value of the site visits, and ensure that the same aspects of each manufacturer’s equipment are reviewed. Notes should be kept, and summarised briefly in writing and circulated for agreement immediately after the visit. CEP08007: March 2009 Purchasing 69 At the site visits, it is important to look at ergonomic aspects of the systems. These can include: • ergonomically designed controls to allow the operator to position the system rapidly and safely with few actions and the minimum of effort (power driven or power assisted movements) • system designed for use by both left and right handed staff • variable height couch to facilitate patient transfer. This is particularly important for patients with limited mobility • access to the patient from both sides of the couch is of particular importance for safe transfer of patients from beds/trolleys to the table • an awareness of the weight, dimensions, handling and likely use of accessories • clearly marked controls in accordance with recognised standards and regulations (such as IEC documents). The site visit is also a chance to get feedback from local users, but any positive or negative comments should always be backed up by evidence. For example, if a user says that “the system is slow”, a practical demonstration of this slowness should be sought. The local users’ comments will also reflect their experience and skill, and that of their staff, and so need to be carefully weighted. More practical advice on conducting a site visit can be found in appendix 6. Tender evaluation and decision making process When purchasing through the European Union procurement process, a list of evaluation criteria, with agreed weightings, will have been sent to all potential suppliers together with the invitation to tender. After return of tenders, some scanners may be eliminated from consideration due to non-conformance with the operational specification, or due to installation or integration issues. The remaining scanners need to be scored according to the agreed criteria. An example scoring sheet is included in appendix 7, adapted from one provided by NHS PASA in the capital investment programme for CT scanners. The evaluation process needs to be fully documented, with a summary made of the evaluation meeting discussions. Local systems should be followed where appropriate. The different options for purchasing through a national framework agreement with NHS Supply Chain involve different levels of decision making processes. CEP08007: March 2009 Purchasing 70 Award of contract The award of the contract will be handled by the procurement department, or their agents. For the European Union purchasing process, complete records of the process, including site visit notes and evaluation scoring must be collated and made available on request to those companies that were not awarded the contract. For more information on procurement please refer to the Department of Health Website. [83]. Project closedown At the end of the project, a closedown meeting should be held with all members of the team. All issues that arose during the project, and their resolution, should be documented. Successful risk mitigations should also be identified. Unresolved issues should be highlighted and discussed. Outstanding issues should be formally handed over to another responsible body in the hospital for resolution, where necessary. A ‘lessons learned’ document should be produced, and useful elements passed on to the relevant parties for inclusion in local procedures and future capital purchase projects. Sustainable procurement The UK Government launched its current strategy for sustainable development, ‘Securing the Future’ in March 2005 [74]. The strategy describes four priorities to progress sustainable development: • sustainable production and consumption – working towards achieving more with less • natural resource protection and environmental enhancement – protecting the natural resources and habitats upon which we depend • sustainable communities – creating places where people want to live and work, now and in the future • climate change and energy – confronting a significant global threat. The strategy also highlights the key role of public procurement in delivering sustainability. The following sections identify relevant sustainability issues and provide some guidance on how these can be incorporated into the CT procurement decision making processes (see also appendix 3). CEP08007: March 2009 Purchasing 71 Energy The key sustainability issue relating to CT scanners is the energy consumption. Scanners use high voltages and currents, and hence can be heavy instantaneous power users. The impact of this on the energy requirements of the department should be considered based on a reasonable expected workload (see appendix 3). Additional power consumption due to air conditioning etc should also be considered. With accessories and other related equipment, there may be the chance to focus on any power saving technologies, such as the use of LCD monitors on workstations and consoles, and LED panel indicators. Wastes and toxic hazards There should be minimal waste products from the scanners themselves. Some scanners use carbon contact brushes on their slip ring power systems. The dust from these rarely causes a problem, but regular cleaning may be required. Other waste includes bedding and contrast agents. X-ray tubes are shielded with lead compounds. These should not produce any hazard in a well maintained system. There should be no other toxic material hazards of note present in the system. Manufacturers can be invited to declare any such hazards in a pre-purchase questionnaire. There may be toxic materials in place in existing building fabrics and scanner suites. Local estates departments should check for such materials before installation and building works commence. End-of-life disposal Consideration should be given to the likely financial and environmental costs of disposal at the end of the product’s life. Where appropriate, suppliers of equipment placed on the market after the 13th August 2005 should be able to demonstrate compliance with the UK Waste Electrical and Electronic Equipment (WEEE) Regulations 2006 [67]. The WEEE regulations place responsibility for financing the cost of collection and disposal on the producer [27]. Electrical and electronic equipment is exempt from the WEEE regulations where it is deemed to be contaminated at the point at which the equipment is scheduled for disposal by the final user. However, if it is subsequently decontaminated, such that it no longer poses an infection risk, it is again covered by the WEEE regulations, and there may be potential to dispose of the unit through the normal WEEE recovery channels. Most CT scanner manufacturers will offer the option to defer cost of disposal, as this is assumed to decrease over the many years of the scanner’s working life. Removal of any existing scanner, and clearance of the scanner suite, should be considered for inclusion in the tender. CEP08007: March 2009 Market review 72 This chapter contains a review of the technical capabilities of MSCT scanners which can acquire 16 slices or more in a single rotation and which are currently being marketed in the UK. At the time of writing, there are four manufacturers in scope: GE Healthcare, Philips Medical Systems, Siemens Medical Solutions and Toshiba Medical Systems. The scanners covered in this report have been divided into the following categories: • • • • • 16 slice scanners 32 to 40 slice scanners 64 slice scanners wide bore scanners 128 to 320 slice scanners. These categories refer to ‘data slices’ acquired in near real time. Some scanners will only achieve these in certain modes. In particular, some of the greater slice numbers may only be for thin slice acquisition, in helical mode. 16 slice CT scanners are currently regarded as good general purpose scanners. They are adequate for most applications, with the exception of some specialist studies, such as cardiac and functional imaging. 32 to 40 slice scanners generally provide a longer coverage per gantry rotation than 16 slice scanners and so result in shorter examination times, with reduced likelihood of motion artefacts. 64 slice scanners provide an added degree of flexibility and are currently the most commonly purchased type of scanner in the UK. They are particularly recommended if cardiac studies are to be performed in a general CT department. Scanners with the capability of acquiring more than 64 slices per rotation are now available. These are specialist systems, currently particularly focussed towards cardiac examinations, but also have applications in perfusion and other functional studies. The number of slices needs to be considered in conjunction with the length of coverage. A greater number of slices may mean longer coverage, or may mean overlapping acquisition data slices due to the dynamic focal spot. Wide bore scanners have a bigger gantry aperture and maximum reconstruction field of view than conventional scanners. The number of slices offered is dependent on the manufacturer. They are generally purchased for radiotherapy planning, as they allow greater flexibility for positioning the patient in the treatment position, but they may also be considered for other applications where the increased aperture and field CEP08007: March 2009 Market review 73 of view are beneficial. These may include imaging bariatric, trauma and intensive care patients. CT scanners are supplied with a couch, a control console, a reconstruction computer and a certain amount of post-processing software. Further specialist post-processing software can be supplied as an option. For more complex processing a dedicated workstation is often purchased. Table 9. Multi-slice CT scanners covered in this guide Category GE Philips Brilliance Siemens Somatom 16 slice BrightSpeed Elite CT 16 Emotion 16 Activion 16 Aquilion 16 32 to 40 slice LightSpeed Select Not applicable Sensation 40 Definition 40 Aquilion 32 64 slice LightSpeed VCT LightSpeed VCT XT CT 64 Sensation 64 Definition AS Definition (dual source) Aquilion 64 Wide bore LightSpeed RT LightSpeed Xtra CT Big Bore Sensation Open 24 Sensation Open 40 Aquilion LB > 64 slice Not applicable iCT Definition AS+ Aquilion ONE Toshiba The scanners available in each category are discussed below and the summary specifications provided in tables at the end of this chapter. The full specifications of the scanners are contained in comparative specification reports [85] - [88]. In addition there is a separate report which contains information on the range of applications software packages available from each manufacturer [84]. As a widely accepted classification, scanner models were originally categorised according to number of image slices that could be reconstructed in one rotation. The number of parallel axial reconstructions from conventional back projection reconstruction methods, are limited to a maximum of about 12, however the number of data channels in helical acquisition are not limited. Therefore number of slices came to mean the number of data channels, or data slices acquired. This has now expanded to accommodate scanners which use the dynamic focal spot in the zdirection to effectively double the number of data slices in real time. One of the primary differentiating factors between the various categories of scanner, and indeed between scanners in each category, is the number of detector banks and the dimensions of the detectors along the scan axis (z-axis). Figure 26 shows a CEP08007: March 2009 Market review 74 schematic example of a multi-slice CT scanner detector array, and Table 10 gives the specific configuration designs for all the scanners covered in this chapter. Figure 26. Schematic diagram of a CT detector array with multiple detector banks along z-axis (not to scale) X-ray tube Detector array x-axis Sub-mm detectors (S) Full extent of detector matrix (F) R rows (z-axis) There is a tendency for a marketing ‘slice wars’ among manufacturers, making it more difficult to uniquely classify scanners. When considering which category of scanner for purchase, it is important to remember that it is not only the number of data slices acquired, but also the length of coverage in one rotation, that are important factors for consideration. Other major features to note, in terms of technical specifications are: the gantry aperture; generator power; anode heat capacity and cooling rate; and gantry rotation speed. Manufacturer’s performance data are often obtained using different methodologies, making direct comparisons unreliable. Image quality is therefore best assessed independently, using a standardised approach. In addition, the computer power of the system will impact on performance. Image reconstruction rates provided give an indication of reconstruction speed, but for a full representation of reconstruction performance in a clinical context, it is best to assess it independently or on a site visit. For further explanations of the technical features please refer to the Technical considerations chapter. The user-friendliness of the systems is an important feature, but is a very subjective element and should also be evaluated during the site visit. CEP08007: March 2009 Market review 75 Table 10. Scanner z-axis detector array configurations Scanner Full coverage (F) Max sub-mm coverage (S) Max number of data ‘slices’ No. of detector rows (R) 16 16 16 16 16 24 24 24 28 40 16 x 1 ( 4 x 5 ) 16 x 2.0 16 ( 20 ) 32 64 40 40 32 64 40 20 64 32 x 1.25 24 x 1.2 † 20 x 0.6 32 x 1.0 40 28.8 12 32 32 x 0.625 † 20 x 0.6 † 20 x 0.6 32 x 0.5 20 12 12 16 64 64 64 64 64 64 64 64 64 64 40 32 40 64 64 x 0.625 64 x 0.625 64 x 0.625 24 x 1.2 32 x 0.6 24 x 1.2 64 x 0.5 40 40 40 28.8 19.2 28.8 32 64 x 0.625 64 x 0.625 64 x 0.625 ‡ 32 x 0.6 32 x 0.6 ‡ 32 x 0.6 64 x 0.5 40 40 40 19.2 19.2 19.2 32 128 128 320 128 64 320 128 x 0.625 64 x 0.6 320 x 0.5 80 40 160 128 x 0.625 64 x 0.6 320 x 0.5 80 40 160 16 16 16 24 40 16 24 24 24 40 40 40 16 x 1.25 16 x 1.25 16 x 1.5 24 x 1.2 24 x 1.2 16 x 2.0 20 20 24 28.8 28.8 32 16 x 0.625 16 x 0.625 16 x 0.75 20 x 0.6 † 20 x 0.6 16 x 0.5 10 10 12 12 12 8 No. channels x detector size (mm) Z-axis Coverage (mm) No. channels x detector size (mm) Z-axis Coverage (mm) 16 x 1.25 16 x 1.5 16 x 1.2 20 24 19.2 16 x 0.625 16 x 0.75 16 x 0.6 16 x 0.5 16 x 0.5 10 12 9.6 8 8 16 slice GE BrightSpeed Elite Philips Brilliance 16 Siemens Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 * * 32 to 40 slice GE LightSpeed VCT Select Siemens Sensation 40 Siemens Definition AS 40 Toshiba Aquilion 32 64 slice GE LightSpeed VCT GE LightSpeed VCT-XT Philips Brilliance 64 Siemens Sensation 64 ‡ Siemens Definition AS 64 ξ Siemens Definition DS Toshiba Aquilion 64 128 to 320 slice ** Philips Brilliance iCT †† Siemens Definition AS+ ‡‡ Toshiba Aquilion ONE Wide bore GE LightSpeed RT 16 GE LightSpeed Xtra Philips Brilliance Big Bore Siemens Sensation Open 24 Siemens Sensation Open 40 Toshiba Aquilion Large Bore † Notes: * Used in brain perfusion scans; Detectors 'double-sampled' with flying focal spot to give 40 (20x2) data acquisition ‡ channels (helical scans); Detectors 'double-sampled' with flying focal spot to give 64 (32 x 2) data acquisition channels ξ ** (helical scans); Dual source. Two X-ray tubes mounted at 90degrees to one another; Detectors 'double-sampled' with †† flying focal spot to give 256 (128 x2) data acquisition channels (helical scans); Detectors 'double-sampled' with flying focal ‡‡ spot to give 128 (64 x 2) data acquisition channels (helical scans); Toshiba allow reconstruction of 640 x 0.5 mm overlapping axial slices from the acquired volume CEP08007: March 2009 Market review 76 16 slice CT scanners Table 11. 16 slice scanners Manufacturer Scanner model GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 The summary technical specifications of 16 slice scanners, listed in Table 11, can be found in Table 16 and a full specification is published in the CEP comparative specification report on 16 slice CT scanners [84]. The z-axis detector array configurations are shown in figure 27. GE, Philips and Siemens each market one scanner in this category, whereas Toshiba offer a lower and higher budget scanner. Toshiba’s lower budget scanner, the Activion 16 has a shorter z-axis coverage than the Aquilion 16, a slower maximum rotation speed, and a less powerful generator and X-ray tube. It does however have the advantages of lower cost and a smaller footprint. Although the Activion 16 routinely acquires data over a z-axis length of 16 mm, the actual extent of its detector array is 20 mm, allowing it to acquire 4 x 5 mm slices in brain perfusion scans. Most of the scanners in this category have full automatic tube current modulation functionality (see Technical considerations), with the exception of the Activion 16, which only has longitudinal (z-axis) tube current modulation. The Brilliance 16 cannot currently perform longitudinal and angular tube current modulation simultaneously. CEP08007: March 2009 Market review 77 Figure 27. 16 slice CT scanner z-axis detector bank configurations GE BrightSpeed Elite 4 x 1.25 mm 16 x 0.625 mm 4 x 1.25 mm 16 data channels: 20 mm coverage, 1.25 mm 10 mm coverage, 0.625 mm Philips Brilliance CT 16 4 x 1.5 mm 16 x 0.75 mm 4 x 1.5 mm 16 data channels: 24 mm coverage, 1.5 mm 12 mm coverage, 0.75 mm Siemens Somatom Emotion 16 4 x 1.2 mm 16 x 0.6 mm 4 x 1.2 mm 16 data channels: 19.2 mm coverage, 1.2 mm 9.6 mm coverage, 0.6 mm Toshiba Activion 16 6 x 1 mm 16 x 0. 5 mm 6 x 1 mm 16 data channels: 16 mm coverage, 1 mm (20 mm coverage, 4 x 5 mm) 8 mm coverage, 0.5 mm Toshiba Aquilion 16 12 x 1 mm 16 x 0. 5 mm 12 x 1 mm z-axis CEP08007: March 2009 16 data channels: 32 mm coverage, 2 mm 16 mm coverage, 1 mm 8 mm coverage, 0.5 mm Market review 78 32 to 40 slice CT scanners Table 12. 32 to 40 slice CT scanners Manufacturer Scanner model GE LightSpeed VCT Select Siemens Somatom Sensation 40 Siemens Somatom Definition AS 40 Toshiba Aquilion 32 The summary specifications of 32 to 40 slice scanners, listed in Table 12, can be found in Table 17 and a full specification is published in the comparative specification report on 32 to 40 slice scanners [86]. The z-axis detector array configurations are shown in Figure 28. The GE and Toshiba scanners have the same detector array configurations as their 64 slice counterparts, but their data acquisition systems limit them to acquiring fewer data channels per rotation. An upgrade to a 64 slice system is available on both scanners. The Siemens Sensation 40 scanner utilises only the central 20 of its 32 submillimetre detector banks for sub-millimetre data acquisition. These 20 detector banks are double-sampled with a z-axis flying focal spot, ‘z-sharp’, to acquire 40 data ‘slices’ per rotation. The Siemens Definition AS 40 has a significantly shorter coverage per rotation than the Sensation 40, but has a wider gantry aperture, a faster rotation speed, a more powerful generator and a higher anode cooling rate. Furthermore it has a faster image reconstruction rate, a higher data transmission rate, higher table load limit and a larger hard disc for image data storage. It is also equipped with the ‘adaptive dose shield’, a dynamic collimator for dose reduction in helical scanning. Philips no longer markets a scanner in this category. All the scanners in this category have full automatic tube current modulation functionality. CEP08007: March 2009 Market review 79 Figure 28. 32 to 40 slice CT scanner z-axis detector bank configuration GE LightSpeed VCT Select 32 data channels: 40 mm coverage, 1.25 mm 20 mm coverage, 0.625 mm 64 x 0.625 mm Siemens Somatom Sensation 40 4 x 1.2 mm 4 x 1.2 mm 32 x 0.6 mm 24 data channels: 28.8 mm coverage,1.2 mm 40 data channels* : 12 mm coverage, 0.6 mm Siemens Somatom Definition AS 40 40 data channels* :12 mm coverage, 0.6 mm 20 x 0.6 mm * 20 detector banks, double -sampled Toshiba Aquilion 32 64 x 0.5 mm 32 data channels: 32 mm coverage, 1 mm 16 mm coverage, 0.5 mm z-axis CEP08007: March 2009 Market review 80 64 slice CT scanners Table 13. 64 slice CT scanners Manufacturer Scanner model GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Toshiba Aquilion 64 The summary specifications of the 64 slice scanners, listed in Table 13, can be found in Table 18, and a full specification is published in the comparative specification report on 64 slice CT scanners [87]. The z-axis detector array configurations are shown in Figure 29. 64 slice scanners are extremely flexible and, with the exception of two of the three Siemens systems in this category, the full length of the detector array can be used to acquire sub-millimetre slices. GE markets two scanners in this category. The LightSpeed VCT XT is the higher specification scanner. The VCT XT is supplied with the 0.35 second rotation time and the VolumeShuttleTM mode as standard. VolumeShuttleTM mode is designed for perfusion scanning; two adjacent 40 mm bands are repeatedly imaged in quick succession, by rapidly alternating the couch position, resulting in an 80 mm long imaged volume. The GE systems can be purchased with an optional 100kW generator providing a higher maximum tube current. The Philips Brilliance 64 has a detector array with the same configuration as that on the GE scanner. Perfusion scanning over an 80 mm long volume can be performed with its ‘Jog scan’ mode. Siemens markets three scanners in this category. The Siemens Sensation 64 and Definition AS 64 are both single X-ray tube systems. The Definition AS 64 has a shorter total z-axis coverage than the Sensation 64. The Siemens Definition, is a dual CEP08007: March 2009 Market review 81 X-ray tube system and will be discussed further in the category covering cardiac CT scanners. The Siemens Definition range of scanners is characterised by the new-style gantry with a wider aperture than the Sensation series. The Definition AS 64 is also equipped with the ‘adaptive dose shield’, a dynamic collimator for dose reduction in helical scanning. The length of coverage for dynamic studies, such as organ perfusion, can be increased using a helical shuttle mode, referred to as ‘Adaptive 4D Spiral’. Most of the scanners in this category have full automatic tube current modulation functionality, with the exception of the Philips scanner, which cannot currently perform longitudinal and angular tube current modulation simultaneously. Figure 29. 64 slice CT scanner z-axis detector bank configurations GE LightSpeed VCT, LightSpeed VCT-XT, Philips Brilliance 64 64 x 0.625 mm 64 data channels: 40 mm coverage, 0.625 mm Siemens Somatom Sensation 64 & Somatom Definition 4 x 1.2 mm 32 x 0.6 mm 4 x 1.2 mm 40 data channels: 28.8 mm coverage, 1.2 mm 64 data channels*: 19.2 mm coverage, 0.6 mm Siemens Somatom Definition AS 64 32 x 0.6 mm 64 data channels*: 19.2 mm coverage, 0.6 mm * 32 detector banks double sampled Toshiba Aquilion 32 & Aquilion 64 64 x 0.5 mm 64 data channels: 32 mm coverage, 0.5 mm z-axis 64 slice cardiac CT scanners A 64 slice scanner is recommended as a minimum for cardiac examinations. Manufacturers usually have products packaged and marketed as ‘cardiac scanners’. These may offer faster rotation times, ECG equipment and cardiac acquisition and reconstruction software as standard. GE market the LightSpeed VCT XT as their specialist cardiac scanner. It is supplied with a 0.35 second rotation time. Its advantage over the LightSpeed VCT is that it can perform prospectively triggered coronary CT angiography (CCTA) scans in CEP08007: March 2009 Market review 82 ‘Snapshot Pulse’ mode. This results in significantly lower doses than retrospectively gated CCTA. GE have also recently a new 64 slice system with a new detector material, dual energy capabilities and new reconstruction approach. No details were available at the time of preparation of this report. Figure 30. Siemens Somatom Definition dual X-ray source CT scanner Tube B Tube A The Siemens Somatom Definition (Figure 30) is the only dual X-ray tube scanner currently available. The two tubes are mounted at an angle of 90° to each other. Tube A has the full 50 cm field of view (FOV) whereas tube B’s FOV is only 26 cm. The Definition has particular advantages in cardiac scanning, despite its relatively short z-axis coverage of 19.2 mm with sub-millimetre slices. Scanning with the two tubes leads to an improvement in the temporal resolution by a factor of two, as compared with a single slice system with the same gantry rotation speed. Because of the high temporal resolution, patients with increased heart rates can be scanned without the administration of beta blocking agents. These patients can also be scanned at higher pitches than on single source systems, resulting in reduced doses. The scanner is capable of dual energy scanning by operating the two tubes at different kilovoltages. It has the most well developed dual energy application software currently on the market. The Definition is also marketed as having advantages when scanning bariatric patients, as the use of the two tubes concurrently can supply double the power of a single source system. Siemens also markets the Somatom Sensation 64 and Somaton Definition AS as cardiac scanners, with fastest rotation times of 0.33 s and 0.3 s respectively. The Brilliance CT 64 with a 0.4 sec rotation time is the Philips 64 slice cardiac scanner. The scanner can perform prospectively triggered cardiac scans in its ‘Step and Shoot’ mode for dose reduction. CEP08007: March 2009 Market review 83 The Toshiba Aquilion 64 cardiac scanner has optional rotation times of 0.35 s, 0.375 s, 0.4 s and 0.45 s available, in addition to the rotation times on their non-cardiac 64 slice system. Most of the scanners in this category have full automatic tube current modulation functionality, with the exception of the Philips scanner, which cannot currently perform longitudinal and angular tube current modulation simultaneously. All the manufacturers have ECG-gated tube current modulation for dose reduction in cardiac studies. On the Siemens Definition range of scanners, the tube current can be reduced to 96% of its peak value, compared to 80% on all the other systems. CEP08007: March 2009 Market review 84 Wide bore CT scanners Table 14. Wide bore CT scanners Manufacturer Scanner model GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB The summary specifications of wide bore scanners, listed in Table 14, can be found in Table 19 and a full specification in the comparative specification report on wide bore CT scanners [88]. The z-axis detector array configurations are shown in Figure 31. Current wide-bore CT scanners acquire between 16 and 40 slices per rotation, depending on the model. Most specifications are similar to those of their standard counterparts. The main difference is a wider gantry aperture and increased reconstruction field of view. Gantry aperture diameters are between 80 and 90 cm, and the maximum reconstruction fields of view, between 65 and 85 cm. Philips and Toshiba market one scanner each in this category, whereas GE and Siemens have two models each. The GE LightSpeed RT is marketed as a radiotherapy planning scanner, whereas the LightSpeed Xtra for trauma and bariatric patients. The Xtra has a bigger generator and a 0.5 s fastest gantry rotation time. On the RT the 0.625 mm slice width is an option, and the fastest rotation time is 0.8s. The main difference between the Sensation Open 24 and 40 is that the Open 40 has the z-sharp technology, enabling double-sampling of the central 20 detectors, resulting in 40 acquired data ‘slices’ per rotation. Most of the scanners in this category have full automatic tube current modulation functionality, with the exception of the Philips scanner, which cannot currently perform longitudinal and angular tube current modulation simultaneously. CEP08007: March 2009 Market review 85 Figure 31. Wide bore CT scanner detector configuration GE LightSpeed RT and LightSpeed Xtra 4 x 1.25 mm 16 x 0.625 mm 4 x 1.25 mm 16 data channels: 20 mm coverage, 1.25 mm 10 mm coverage, 0.625 mm Philips Brilliance CT Big Bore 4 x 1.5 mm 16 x 0.75 mm 4 x 1.5 mm Siemens Somatom Sensation Open 24 and 40 4 x 1.2 mm 32 x 0.6 mm 4 x 1.2 mm 16 data channels: 24 mm coverage, 1.5 mm 12 mm coverage, 0.75 mm Open 24 24 data channels: 28.8 mm coverage,1.2 mm 20 data channels : 12 mm coverage, 0.6 mm Open 40 24 data channels: 28.8 mm coverage,1.2 mm 40 data channels* : Toshiba Aquilion LB 12 x 1 mm 16 x 0. 5 mm 12 x 1 mm 16 data channels: 32 mm coverage, 2 mm 16 mm coverage, 1 mm 8 mm coverage, 0.5 mm z-axis CEP08007: March 2009 * 20 detector banks double sampled Market review 86 Greater than 64 slice CT scanners Table 15. Greater than 64 slice scanners Manufacturer Scanner model IGE 750 HD Philips Brilliance iCT Siemens Definition AS+ Toshiba Aquilion ONE A few scanners capable of acquiring more than 64 data slices per rotation have recently been introduced. These can be considered specialist scanners. These are listed in Table 15. The summary specifications of these scanners can be found in Table 20 and a full specification in the comparative specification report on 128 to 320 slice scanners [89]. The z-axis detector array configurations are shown in Figure 32. The Philips Brilliance iCT was launched at RSNA 2007 and is likely to be commercially available in 2009. The scanner has a coverage of 80 mm, with a detector array consisting of 128 x 0.625 mm detector elements along the z-axis. It employs a z-axis flying focal spot, which doubles the number of channels acquired in a single rotation, thereby making it a ‘256 slice’ scanner. It has a new design of X-ray tube for improved stability of focal spot and a two layered detector for dual energy scanning. It also has a maximum gantry rotation speed of 0.27 s, the fastest on the market. The Siemens Definition AS+ has a maximum z-axis coverage of 38.4 mm with 64 x 0.6 mm detectors. It employs a z-axis flying focal spot, and so acquires 128 data channels from the 64 detector banks, making it into a ‘128 slice’ scanner. The scanner has a maximum gantry rotation speed of 0.3 s and utilises the ‘adaptive dose shield’ to reduce doses in helical scanning. The Toshiba Aquilion ONE, has a z-axis coverage of 160 mm, with 320 x 0.5 mm detector elements. It can reconstruct 640 slices from a single axial rotation, and could perhaps be termed a ‘640 slice scanner’. The 160 mm detector array length enables the coverage of whole organs such as the heart, liver and brain in a single gantry rotation. The scanner has particular applications in cardiology and functional studies such as brain and liver perfusion. CEP08007: March 2009 Market review 87 Figure 32. CT scanners with 128 to 320 data slices: z-axis detector bank configurations Philips Brilliance iCT 128 x 0.625 mm 256 data channels*: 80 mm coverage, 0.625 mm * 128 detector banks double-sampled Siemens Somatom Definition AS+ 64 x 0.6 mm 128 data channels**: 38.4 mm coverage, 0.6 ** 64 detector banks double-sampled Toshiba Aquilion 320 data channels***: 160 mm coverage, 0.5 mm 320 x 0.5 mm *** capable of 640 slices from one axial acquisiiton z-axis CEP08007: March 2009 Market review 88 Summary specifications Tables 16 - 20 summarise the technical and application specification data collected from the manufacturers. Some key factors are given to allow a basic comparison between scanner models. The scanners are presented in categories as described previously. Full technical and application specifications are available separately [84]-[89]. Table 16: Summary specifications of 16 slice CT scanners GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 Scanner type 16 slice 3rd gen 16 slice 3rd gen 16 slice 3rd gen 16 slice 3rd gen 16 slice 3rd gen Gantry aperture [cm] 70 70 70 72 72 Gantry tilt - Sequential/Helical [degrees] ±30° for both ±30° sequential ±30° for both ±30° for both ±30° for both Power rating [kW] 53.2 60 50 42 60 Anode heat capacity [MHU] 6.3 8 5 4 7.5 Maximum anode cooling rate [kHU / min] 840 1608 810 864 1386 Scanner gantry X-ray generator and tube CEP08007: March 2009 Market review 89 GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 Detector type Solid state Solid state array Solid state array Solid state array Solid state array Detector array configuration (# x width [mm]) 32 x 0.625 16 x 0.75 8 x 1.5 16 x 0.6 8 x 1.2 16 x 0.5 12 x 1.0 16 x 0.5 24 x 1.0 Maximum z-axis coverage [mm] 20 24 19.2 20 32 Max z-axis coverage with sub-mm slices [mm] 10 12 9.6 8 8 Length & width [cm] 239 x 42 243 x 41 218 x 43 219 (std) or 189 (short) x 47 219 (std) or 189 (short) x 47 Maximum scannable range [cm] 170 (Axial) 160 (Helical) 192 153 175 (std) 145 (short) 175 (std) 145 (short) Minimum height out of gantry [cm] 51 52 45 31 31 Maximum weight on couch [kg] 205 204 200 205 205 Minimum rotation time in helical mode [s] 0.5 0.5 (0.4 option) 0.6 (0.5 option) 0.75 0.5 (0.4) option Kilovoltage settings [kV] 80, 100, 120, 140 90, 120, 140 80, 110, 130 80, 100, 120, 135 80, 100, 120, 135 Tube current range at 120/130 kV [mA] 10 - 440 30 - 500 20 - 345 10 - 300 10 - 500 Detection system Couch Scan parameters CEP08007: March 2009 Market review 90 GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 Reconstruction field of view range [cm] 9.6 - 50 5 - 50 Std & High res 2.5 - 25 Ultra High res (UHR) 5.0 - 50 5 -50 5 - 50 Reconstruction matrices 512 x 512 512 x 512 (768 x 768 & 1024 x 1024 option) 512 x 512 512 x 512 512 x 512 Recon rate for std head scan, 5122 [images/s] Up to 6 (up to 16 option) ~6 (~ 15 option) 16 6 4 Recon rate for std body scan, 5122 [images/s] Up to 6 (up to 16 option) ~6 (~ 14 option) 16 6 4 Image reconstruction CEP08007: March 2009 Market review 91 GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 Tube current modulation (x-y & z) x-y & z x-y & z, but not simultaneously x-y & z z x-y & z Adaptive collimators in helical scanning No No No No No Standard total hard disc capacity [GB] 291 392 965 297 450 Ability to burn images to disc Yes Option Yes Yes Yes 12 Maximum 50 (enhanced DICOM, optional) Yes Dose reduction features Data management & connectivity Rate of image transfer: scanner to workstation [images/s] 16 Network dependent up to 25 12 Maximum 50 (enhanced DICOM, optional) IHE scheduled workflow supported Yes Yes Yes Yes CEP08007: March 2009 Market review 9 GE BrightSpeed Elite Philips Brilliance CT 16 Siemens Somatom Emotion 16 Toshiba Activion 16 Toshiba Aquilion 16 Scan plane limiting clinical spatial resolution [mm] 0.324 (15.4 lp/cm @ 0% MTF) 0.22 (23 lp/cm @ 2% MTF) 0.32 (15.6 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) Longitudinal (z-axis) limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.33 (15 lp/cm @ 0% MTF) 0.33 (15 lp/cm @ 2% MTF) Info not available Info not available Contrast resolution: smallest rod size discernable [mm @ 0.3% contrast @ x mGy surface dose in Catphan] 5mm @ 0.3% w/o any noise filter,120kV, 13.3mGy, 10mm 5 mm @ 0.3% @ 19 mGy 5 mm @ 0.3% @ 16 mGy 3 mm @ 0.3% @ 16.4 mGy 4 mm @ 0.3% @ 10.0 mGy; FC41 kernel with 3D adaptive filter Do not use for direct dose comparisons* 19.6 @120 kV 12.9 @120 kV 24.4 @ 130 kV 22.7 @ 120 kV 20.5 @ 120 kV CTDIw for standard body scan [mGy/100mAs] Do not use for direct dose comparisons* 9.9 @120 kV 6.5 @ 120 kV 7.6 @ 130 kV 10.2 @ 120 kV 12.1 @ 120 kV 3 phase 200-480 V, 90 kVA 3 phase 200 - 500 V 100 kVA 3 phase 380 - 440 V 70 kVA 3 phase 380 - 440 V 75 kVA 3 phase 380 - 440 V 100 kVA Minimum floor load-bearing [kg/m²] 1290 Info not available 428 670 732 Recommended floor area for scanner [m²] 3.7 m x 6.1 m 35.7 14 minimum 22 (std couch) 21 (short couch) 27 (std couch) 25 (short couch) Manufacturer's performance data CTDIw for standard head scan [mGy/100mAs] Room requirements Power requirements (gantry) * These figures do not reflect the scanners' dose efficiency. A relative patient dose at the stated kV can be calculated using this data in conjunction with the recommended clinical scan parameters (mAs, pitch) CEP08007: March 2009 Market review 93 Table 17. Summary specifications of 32 to 40 slice CT scanners GE LightSpeed VCT Select Siemens Somatom Sensation 40 Siemens Somatom Definition AS 40 Toshiba Aquilion 32 Scanner type 32 slice 3rd gen 40 slice 3rd gen 40 slice 3rd gen 32 slice 3rd gen Gantry aperture [cm] 70 70 78 72 Gantry tilt - Sequential/Helical [degrees] ±30° sequential ±30° sequential ±30° sequential ±30° for both Power rating [kW] 100 70 80 60 (72 option) Anode heat capacity [MHU] 8 0.6 (equiv to 30) 0.6 (equiv to 30) 7.5 Maximum anode cooling rate [kHU / min] 2100 5000 7300 1386 Detector type Solid state Solid state array Solid state array Solid state array Detector array configuration (# x width [mm]) 32 x 0.625 16 x 1.25 32 x 0.6 8 x 1.2 20 x 0.6 Maximum z-axis coverage [mm] 40 28.8 12 32 Max z-axis coverage with sub-mm slices [mm] 20 12 12 16 Scanner gantry X-ray generator and tube Detection system CEP08007: March 2009 0.5 x 64 Market review 94 GE LightSpeed VCT Select Siemens Somatom Sensation 40 Siemens Somatom Definition AS 40 Toshiba Aquilion 32 Length & width [cm] 285 x 42 243 x 40 240 x 45 (std) 240 x 53 (multipurpose) 219 (std) or 189 (short) x 47 Maximum scannable range [cm] 170 med table 200 long table 157 160 (200 option) 175 (std) 145 (short) Minimum height out of gantry [cm] 43 53 48 (53 multipurpose) 31 Maximum weight on couch [kg] 227 200 (280 option) 220 (300 option) 205 Minimum rotation time in helical mode [s] 0.4 (0.35 option) 0.37 0.33 0.5 (0.35 option) Kilovoltage settings [kV] 80, 100, 120, 140 80, 100, 120, 140 80, 100, 120, 140 80, 100, 120, 135 Tube current range at 120/130 kV [mA] 10 - 800 28 - 580 20 - 666 10 - 500 (10 - 600 option) Couch Scan parameters CEP08007: March 2009 Market review 95 GE LightSpeed VCT Select Siemens Somatom Sensation 40 Siemens Somatom Definition AS 40 Toshiba Aquilion 32 Reconstruction field of view range [cm] 9.6 - 50 5 - 50 (70 option) 5 - 50 (78 option) 5 - 50 Reconstruction matrices 512 x 512 512 x 512 512 x 512 512 x 512 Recon rate for std head scan, 5122 [images/s] up to 6 (16 option) 20 40 16 Recon rate for std body scan, 5122 [images/s] up to 6 (16 option) 20 40 16 Tube current modulation (x-y & z) x-y & z x-y & z x-y & z x-y & z Adaptive collimators in helical scanning No No Yes No Standard total hard disc capacity [GB] 584 1022 1241 1245 Ability to burn images to disc Yes Yes Yes Yes Rate of image transfer: scanner to workstation [images/s] up to 16 up to 25 up to 25 12 Maximum 50 (enhanced DICOM, optional) IHE scheduled workflow supported Yes Yes Yes Yes Image reconstruction Dose reduction features Data management & connectivity CEP08007: March 2009 Market review 96 GE LightSpeed VCT Select Siemens Somatom Sensation 40 Siemens Somatom Definition AS 40 Toshiba Aquilion 32 Scan plane limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.21 (23.7 lp/cm @ 2% MTF) 0.21 (24 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) Longitudinal (z-axis) limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.24 (21 lp/cm @ 2% MTF) 0.24 (21 lp/cm @ 2% MTF) Info. not available Contrast resolution: smallest rod size discernable [mm @ 0.3% contrast @ x mGy surface dose in Catphan] 3 mm @ 0.3% @ 20.5 mGy CTDIvol 5 mm @ 0.3% @ 17 mGy 5 mm @ 0.3% @ 16 mGy 4 mm @ 0.3% @ 10.0 mGy; FC41 kernel with 3D adaptive filter CTDIw for standard head scan [mGy/100mAs] Do not use for direct dose comparisons* 19.3 @ 120 kV 13.5 @ 120 kV 16.6 @ 120 kV 20.5 @120 kV CTDIw for standard body scan [mGy/100mAs] Do not use for direct dose comparisons* 8.6 @ 120 kV 6.7 @ 120 kV 7.5 @ 120 kV 12.1 @120 kV Power requirements (gantry) 3 phase 380-480 V 150 kVA 3 phase 380 - 480 V 104 kVA 3 phase 380 - 480 V 125 kVA 3 phase 380 - 440 V, 100 kVA Minimum floor load-bearing [kg/m²] 1448 294 333 732 Recommended floor area for scanner [m²] 21.7 med table 23.8 long table 17.5 minimum 18 mininum 27 (std couch) 25 (short couch) Manufacturer's performance data Room requirements * These figures do not reflect the scanners' dose efficiency. A relative patient dose at the stated kV can be calculated using this data in conjunction with the recommended clinical scan parameters (mAs, pitch) CEP08007: March 2009 Market review 97 Table 18. Summary specifications of 64 slice CT scanners GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Scanner type 64 slice 3rd gen 64 slice 3rd gen 64 slice 3rd gen 64 slice 3rd gen 64 slice 3rd gen Dual source 3rd gen 64 slice 3rd gen Gantry aperture [cm] 70 70 70 70 78 78 72 Gantry tilt - Sequential/Helical [degrees] ±30° sequential ±30° sequential ±30° sequential ±30° sequential ±30° sequential No ±30° for both Power rating [kW] 85 (100 option) 100 60 80 80 80 (x2) 60 (72 option) Anode heat capacity [MHU] 8 8 8 0.6 (equiv to 30) 0.6 (equiv to 30) 0.6 (equiv to 30) 7.5 Maximum anode cooling rate [kHU / min] 2100 2100 1608 5000 7300 7300 1386 Scanner gantry X-ray generator and tube CEP08007: March 2009 Market review 98 GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Detector type Solid state Solid state Solid state array Solid state array Solid state array Solid state array Solid state array Detector array configuration (# x width [mm]) 64 x 0.625 64 x 0.625 64 x 0.625 32 x 0.6 8 x 1.2 32 x 0.6 32 x 0.6 (x 2) 8 x 1.2 (x 2) 64 x 0.5 Maximum z-axis coverage [mm] 40 40 40 28.8 19.2 28.8 (x2) 32 Max z-axis coverage with sub-mm slices [mm] 40 40 40 19.2 19.2 19.2 (x2) 32 Length & width [cm] 285 x 42 285 x 42 243 x 41 240 x 40 240 x 45 (std) 240 x 53 (multipurpose) 240 x 45 (std) 240 x 53 (multipurpose) 219 (std) or 189 (short) x 47 Maximum scannable range [cm] 170 med table 200 long table 170 med table 200 long table 175 157 160 (200 option) 200 175 (std) 145 (short) Minimum height out of gantry [cm] 43 43 57.8 53 48 (53 multipurp.) 48 (53 multipurp.) 31 Maximum weight on couch [kg] 227 227 204 (295 option) 200 (280 option) 220 (300 option) 220 (300 option) 205 Detection system Couch CEP08007: March 2009 Market review 99 GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Minimum rotation time in helical mode [s] 0.4 (0.35 option) 0.35 0.5 (0.4 option) 0.33 0.3 0.33 0.5 (0.35 option ) Kilovoltage settings [kV] 80, 100, 120, 140 80, 100, 120, 140 90, 120, 140 80, 100, 120, 140 80, 100, 120, 140 80, 100, 120, 140 80, 100, 120, 135 Tube current range at 120/130 kV [mA] 10 - 700 (800 option) 10 - 800 20 - 500 28 - 665 20 - 666 20 - 666 (x2) 10 - 500 (10 - 600 option) 5 - 50 (70 option) 5 - 50 (78 option) 5 - 50 (78 option) 5 - 50 Scan parameters Image reconstruction Reconstruction field of view range [cm] 9.6 - 50 9.6 - 50 5 - 50 Std & high res 2.5 - 25 Ultra high res (UHR) Reconstruction matrices 512 x 512 512 x 512 512 x 512, 768 x 768 & 1024 x 1024 512 x 512 512 x 512 512 x 512 512 x 512 Recon rate for std head scan, 5122 [images/s] 16 16 ~ 18 20 40 40 16 Recon rate for std body scan, 5122 [images/s] up to 6 (16 option) up to 16 ~ 16 20 40 40 16 CEP08007: March 2009 Market review 100 GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Tube current modulation (x-y & z) x-y & z x-y & z x-y & z, but not simultaneously x-y & z x-y & z x-y & z x-y & z Adaptive collimators in helical scanning No No No No Yes No No Standard total hard disc capacity [GB] 584 584 880 1022 1241 1825 1245 Ability to burn images to disc Yes Yes Option Yes Yes Yes Yes Dose reduction features Data management & connectivity Rate of image transfer: scanner to workstation [images/s] up to 16 up to 16 Network dependent up to 25 up to 25 up to 25 12 Maximum 50 (enhanced DICOM, optional) IHE scheduled workflow supported Yes Yes Yes Yes Yes Yes Yes CEP08007: March 2009 Market review 101 GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Scan plane limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.35 (14.2 lp/cm @ 4% MTF) 0.22 (23 lp/cm @ 2% MTF) 0.21 (23.7 lp/cm @ 2% MTF) 0.21 (24 lp/cm @ 2% MTF) 0.21 (24.3 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) Longitudinal (z-axis) limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.35 (14.2 lp/cm @ 4% MTF) 0.33 (15 lp/cm @ 0% MTF) 0.24 (21 lp/cm @ 2% MTF) 0.24 (21 lp/cm @ 2% MTF) 0.24 (21 lp/cm @ 2% MTF) Info. not available Contrast resolution: smallest rod size discernable [mm @ 0.3% contrast @ x mGy surface dose in Catphan] 3 mm @ 0.3% @ 22.2 mGy CTDIvol 3 mm @ 0.3% @ 22.2 mGy CTDIvol 5 mm @ 0.3% @ 19 mGy 5 mm @ 0.3% @ 17 mGy 5 mm @ 0.3% @ 16 mGy 5 mm @ 0.3% @ 17 mGy 4 mm @ 0.3% @ 10.0 mGy; FC41 kernel with 3D adaptive filter CTDIw for standard head scan [mGy/100mAs] Do not use for direct dose comparisons* 19.3 @ 120 kV 19.3 @ 120 kV 10.9 @ 120 kV 13.5 @ 120 kV 16.6 @ 120 kV 13.5 @ 120 kV 20.5 @120 kV CTDIw for standard body scan [mGy/100mAs] Do not use for direct dose comparisons* 8.6 @ 120 kV 8.6 @ 120 kV 5.6 @ 120 kV 6.7 @ 120 kV 7.5 @ 120 kV 7.3 @ 120 kV 12.1 @120 kV Manufacturer's performance data CEP08007: March 2009 Market review 102 GE LightSpeed VCT GE LightSpeed VCT XT Philips Brilliance CT 64 Siemens Somatom Sensation 64 Siemens Somatom Definition AS 64 Siemens Somatom Definition Dual Source Toshiba Aquilion 64 Power requirements (gantry) 3 phase 380-480 V 150 kVA 3 phase 380-480 V 150 kVA 3 phase 200 - 500 V 100 kVA 3 phase 380 - 480 V 104 kVA 3 phase 380 - 480 V Neutral & Earth 50 Hz 3 phase 380 - 480 V Neutral & Earth 50 Hz 3 phase 380 - 440 V, 100 kVA Minimum floor load-bearing [kg/m²] 1448 1448 Info not available 294 333 Up to 517.2 ±10% 732 Recommended floor area for scanner [m²] 21.7 med table 23.8 long table 21.7 med table 23.8 long table 35.7 17.5 minimum 18 minimum 17.7 minimum 27 (std couch) 25 (short couch) Room requirements * These figures do not reflect the scanners' dose efficiency. A relative patient dose at the stated kV can be calculated using this data in conjunction with the recommended clinical scan parameters (mAs, pitch) CEP08007: March 2009 Market review 103 Table 19. Summary specifications of wide bore CT scanners GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Scanner type 16 slice wide bore 3rd gen 16 slice wide bore 3rd gen 16 slice wide bore 3rd gen 24 slice wide bore 3rd gen 40 slice wide bore 3rd gen 16 slice wide bore 3rd gen Gantry aperture [cm] 80 80 85 82 82 90 Gantry tilt - Sequential/Helical [degrees] ±30° sequential ±30° sequential ±30° sequential ±30° sequential ±30° sequential Not available Power rating [kW] 53.2 100 48 50 50 60 Anode heat capacity [MHU] 8 MHU 8 MHU 8 0.6 (equiv to 30) 0.6 (equiv to 30) 7.5 Maximum anode cooling rate [kHU / min] 648 648 1608 5000 5000 1386 Scanner gantry X-ray generator and tube CEP08007: March 2009 Market review 104 GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Detector type Solid state Solid state Solid state array Solid state array Solid state array Solid state array Detector array configuration (# x width [mm]) 16x 0.625mm 8x 1.25mm 16x 0.625mm 8x 1.25mm 16 x 0.75 8 x 1.5 32 x 0.6 8 x 1.2 32 x 0.6 8 x 1.2 16x 0.5 24x 1.0 Maximum z-axis coverage [mm] 20 20 24 28.8 28.8 32 Max z-axis coverage with sub-mm slices [mm] 10 10 12 12 12 8 Length & width [cm] 239 x 42 med 292 x 42 long 239 x 42 med 292 x 42 long 243 x 41 240 x 40 (240 x 53 RT option) 240 x 40 (240 x 53 RT option) 219 (std) or 189 (short) x 47 Maximum scannable range [cm] 170 med table 200 long table 170 med table 200 long table 175 157 157 175 (std) 145 (short) 53 (65 with high capacity table option) 31 200 (280 option) 205 Detection system Couch Minimum height out of gantry [cm] 43 43 57.8 53 (65 with high capacity table option) Maximum weight on couch [kg] 227 227 295 200 (280 option) CEP08007: March 2009 Market review 105 GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Minimum rotation time in helical mode [s] 0.8 0.5 0.44 0.5 0.5 0.5 Kilovoltage settings [kV] 80, 100, 120, 140 80, 100, 120, 140 90, 120, 140 80, 100, 120, 140 80, 100, 120, 140 80, 100, 120, 135 Tube current range at 120/130 kV [mA] 10 - 440 10 - 800 20 - 500 28 - 400 28 - 400 10 - 500 Reconstruction field of view range [cm] 9.6 - 65 9.6 - 65 5 - 60 5 - 50 (5 - 82 option) 5 - 50 (5 - 82 option) 5 - 50 Reconstruction matrices 512 x 512 512 x 512 512 x 512, 768 x 768 & 1024 x 1024 512 x 512 512 x 512 512 x 512 Recon rate for std head scan, 5122 [images/s] up to 6 (16 option) up to 6 (16 option) ~10 20 20 4 Recon rate for std body scan, 5122 [images/s] up to 6 (16 option) up to 6 (16 option) ~6 20 20 4 Scan parameters Image reconstruction CEP08007: March 2009 Market review 106 GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Tube current modulation (x-y & z) x-y & z x-y & z x-y & z, but not simultaneously x-y & z x-y & z x-y & z Adaptive collimators in helical scanning No No No No No No Standard total hard disc capacity [GB] 291 291 392 1022 1022 450 Ability to burn images to disc Yes Yes Yes Yes Yes Yes Rate of image transfer: scanner to workstation [images/s] 6 std (up to 16 option) 6 std (up to 16 option) Network dependent up to 25 up to 25 12 Maximum 50 (enhanced DICOM, optional) IHE scheduled workflow supported Yes Yes Yes Yes Yes Yes Dose reduction features Data management & connectivity CEP08007: March 2009 Market review 107 GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Scan plane limiting clinical spatial resolution [mm] 0.35 (14.2 lp/cm @ 4% MTF) 0.35 (14.2 lp/cm @ 4% MTF) 0.33 (15 lp/cm @ 2% MTF) 0.34 (14.7 lp/cm @ 2% MTF) 0.34 (14.7 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) Longitudinal (z-axis) limiting clinical spatial resolution [mm] 0.35 +/- 0.05 mm (visual) 0.35 +/- 0.05 mm (visual) 0.56 (9 lp/cm @ 0% MTF) 0.29 (17 lp/cm @ 2% MTF) 0.29 (17 lp/cm @ 2% MTF) Info. not available Contrast resolution: smallest rod size discernable [mm @ 0.3% contrast @ x mGy surface dose in Catphan] 3mm @ 0.45% @ 37.2mGy 3mm @ 0.45% @ 37.2mGy 3.5 @ 0.35% Dose not available 5 mm @ 0.3% @ 17 mGy 5 mm @ 0.3% @ 17 mGy 4 mm @ 0.3% @ 11.9 mGy; FC41 kernel with 3D adaptive filter CTDIw for standard head scan [mGy/100mAs] Do not use for direct dose comparisons* 13.94 @ 120 kV 13.94 @ 120 kV Info not available 17.5 @ 120 kV 19.4 @ 120 kV 15.9 @120 kV CTDIw for standard body scan [mGy/100mAs] Do not use for direct dose comparisons* 7.33 @ 120 kV 7.33 @ 120 kV Info not available 9.3 @ 120 kV 8.5 @ 120 kV 10.8 @120 kV Manufacturer's performance data CEP08007: March 2009 Market review 108 GE LightSpeed RT GE LightSpeed Xtra Philips Brilliance CT Big Bore Siemens Somatom Sensation Open 24 Siemens Somatom Sensation Open 40 Toshiba Aquilion LB Power requirements (gantry) 3 phase 380-480 V 150 kVA 3 phase 380-480 V 150 kVA 3 phase 200 - 500 V 100 kVA 3 phase 380 - 480 V 66 - 80 kVA 3 phase 380 - 480 V 66 - 80 kVA 3 phase 380 - 440 V, 100 kVA Minimum floor load-bearing [kg/m²] 1337 1337 Info not available 293.7 ±10% 293.7 ±10% 923 Recommended floor area for scanner [m²] 26 med table 28.6 long table 26 med table 28.6 long table Info not available 17.5 minimum 17.5 minimum 27 (std couch) 25 (short couch) Room requirements * These figures do not reflect the scanners' dose efficiency. A relative patient dose at the stated kV can be calculated using this data in conjunction with the recommended clinical scan parameters (mAs, pitch) CEP08007: March 2009 Market review 109 Table 20. Summary specifications CT scanners with more than 64 slices Philips Brilliance iCT Siemens Somatom Definition AS+ Toshiba Aquilion ONE Scanner type 256 slice, 3rd gen 128 slice, 3rd gen 320 slice, 3rd gen Gantry aperture [cm] 70 78 72 Gantry tilt - Sequential/Helical [degrees] Not available ±30° sequential ±22° sequential Power rating [kW] 120 100 70 Anode heat capacity [MHU] Equiv to 30 0.6 (equiv to 30) 7.5 Maximum anode cooling rate [kHU / min] 1608 7300 1386 Detector type Solid state Solid state Solid state Detector array configuration (# x width [mm]) 128 x 0.625 64 x 0.6 320 x 0.5 Maximum z-axis coverage [mm] 80 38.4 160 Max z-axis coverage with sub-mm slices [mm] 80 38.4 160 Greater than 64 slice Scanner gantry X-ray generator and tube Detection system CEP08007: March 2009 Market review 110 Philips Brilliance iCT Siemens Somatom Definition AS+ Toshiba Aquilion ONE Length & width [cm] 243 x 41 240 x 45 240 x 53 (multipurpose) 246 x 47 Maximum scannable range [cm] 175 160 (200 option) 195 Minimum height out of gantry [cm] 57.8 48 (53 with multipurpose table option) 33 Maximum weight on couch [kg] 204 220 (300 option) 300 (230 within spec) Minimum rotation time in helical mode [s] 0.33 (0.27 option) 0.3 0.35 Kilovoltage settings [kV] 80, 120, 140 80, 100, 120, 140 80, 100, 120, 135 Tube current range at 120/130 kV [mA] 10 - 1000 20 - 800 10 - 580 Greater than 64 slice Couch Scan parameters CEP08007: March 2009 Market review 111 Philips Brilliance iCT Siemens Somatom Definition AS+ Toshiba Aquilion ONE Reconstruction field of view range [cm] 5 - 50 5 - 50 (78 option) 5 - 50 Reconstruction matrices 512 x 512 768 x 768 1024 x 1024 512 x 512 512 x 512 Recon rate for std head scan, 5122 [images/s] Approx 20 40 32 Recon rate for std body scan, 5122 [images/s] Approx 18 40 32 Tube current modulation (x-y & z) x-y & z but not simultaneously x-y & z x-y & z Adaptive collimators in helical scanning Yes Yes No Standard total scanner hard disc storage capacity [GB] 292 (host) 588 (on recon computer) 1679 3800 Ability to burn images to disc Yes Yes Yes Rate of image transfer: scanner to workstation [images/s] Info not available up to 25 50 max IHE scheduled workflow supported Yes Yes Yes Greater than 64 slice Image reconstruction Dose reduction features Data management & connectivity CEP08007: March 2009 Market review 112 Philips Brilliance iCT Siemens Somatom Definition AS+ Toshiba Aquilion ONE Scan plane limiting clinical spatial resolution [mm] 0.22 (23 lp/cm @ 2% MTF) 0.21 (24 lp/cm @ 2% MTF) 0.23 (21.4 lp/cm @ 2% MTF) Longitudinal (z-axis) limiting clinical spatial resolution [mm] Info not available 0.24 (21 lp/cm @ 2% MTF) 0.35 (14.4 lp/cm @ 2% MTF) Contrast resolution: smallest rod size discernable [mm @ 0.3% contrast @ x mGy surface dose in Catphan] 5 mm @ 0.3% @ 18 mGy 5 mm @ 0.3% @ 16 mGy 4 mm @ 0.3% @ 10.0 mGy; FC41 kernel with 3D adaptive filter CTDIw for standard head scan [mGy/100mAs] Do not use for direct dose comparisons* 10.9 @ 120 kV 16.6 @ 120 kV Not applicable CTDIw for standard body scan [mGy/100mAs] Do not use for direct dose comparisons* 5.6 @ 120 kV 6.7 @ 120 kV Not applicable Power requirements (gantry) 3 phase 200 - 500 V AC, 225 kVA 50/60 Hz 3 phase 380 - 480 V Neutral & Earth 50 Hz 3 phase 380 - 440 V, 100 kVA Minimum floor load-bearing [kg/m²] 729.7 Up to 333.33 ±10% 1070 Recommended floor area for scanner [m²] 41.4 18 min 43 Greater than 64 slice Manufacturer's performance data Room requirements * These figures do not reflect the scanners' dose efficiency. A relative patient dose at the stated kV can be calculated using this data in conjunction with the recommended clinical scan parameters (mAs, pitch) CEP08007: March 2009 Acknowledgements 113 We should like to thank the following for their contributions to this buyers’ guide. Jane Adam, Alan Britten, Linda Howarth and Andrew Stewart, St Georges Healthcare NHS Trust Elmer Bakker and Graham Dickinson, Centre for Research in Strategic Purchasing and Supply (CRiSPS), University of Bath Roger Bury, Royal College of Radiologists Jackie Bye, Lindsey Carver, and Sandie Jewell, GE Healthcare Matthew Dunn, IPEM – Diagnostic radiology special interest group Thomas Flohr and Susie Guthrie, Siemens Medical Solutions Kate Garras, Society and College of Radiographers Alistair Howseman and Derek Tarrant, Philips Medical Systems Tarun Mittal, British Society of Cardiovascular Imaging Andrew Reilly, British Institute of Radiology Lisa Smith, NHS Improvement - Radiology Service Improvement Team Marie Whittaker, NHS Supply Chain CEP08007: March 2009 Glossary 114 3D imaging techniques used to display images of a three dimensional volume on a flat (2D) display, such as a computer screen. Should be distinguished from true 3D displays, such as virtual reality or stereoscopic systems. 3rd generation describes a CT scanner design with a rotating tube detector assembly. The design for all modern CT scanners ALARA as low as reasonably achievable ALARP as low as reasonably practicable anterioposterior (AP) from the front (anterior) towards the back (posterior) of a patient. Common orientation for SPR images archive storage of large amounts of idle data. Accuracy of data recovery is important, but as the data are no longer active, speed of reading is not as important Can by on various types of devices or media, such as tape. as low as reasonably achievable / practicable (ALARA /ALARP) principle used in radiation protection that the patient dose should always be the minimum required to achieve the clinical objective BIR British Institute of Radiology BNMS British Nuclear Medicine Society CD compact disc CE Conformité Européene CEP Centre for Evidence-based Purchasing CT computed tomography CTC CT colonography CTDI computed tomography dose index CTDIvol volume computed tomography dose index CTPA CT pulmonary angiography Caldicott guardian a senior staff member responsible for protecting the confidentiality of patient information, and enabling appropriate information-sharing cannulation procedure involving insertion of a flexible catheter into one of the large blood vessels Catphan® standard test object used to measure some of the performance aspects of CT scanners CE marking Indication of compliance with relevant EU directives, in particular the MDD. CEP08007: March 2009 Glossary 115 (low) contrast resolution the minimum difference in material attenuation (CT number) that is perceptible between adjacent pixels in an image matrix computed tomography (CT) an imaging technique that uses views of an object from many directions to synthesise a transaxial or cross sectional image computed tomography dose index (CTDI) a term used in radiation dosimetry that defines the adsorbed dose from a single rotation of a CT scanner. There are a number of definitions of CTDI commonly used cone-beam reconstruction techniques for reconstructing images from ‘non-parallel’ projection data contrast medium a substance introduced into structures to increase or decrease their contrast, enhancing resolution on the CT image. Most commonly a radio-opaque substance is injected intravenously, but oral contrast may also be used coronary angiography imaging the vessels of the heart coronary calcium scoring technique to determine whether or not coronary artery disease is present, by measuring the deposition of calcium in arterial walls CT colonography using a CT scanner to produce non-invasive slice and 3D images of the colon and rectum (virtual colonoscopy) CT fluoroscopy use of CT to produce real-time images DH (UK) Department of Health DICOM digital imaging and communication in medicine. DLP dose-length product DRL diagnostic reference level DSoN detailed statement of needs DVD digital versatile disc detailed statement of need (DSoN) a procurement document that gives a details of the requirements for the equipment . Current advice prefers an output-based specification (OBS) approach detectors the part of the scanner that senses the transmitted X-rays and generates an electrical signal detector array the matrix of detector elements in the detector system of the scanner DICOM object the defined structure of data within DICOM imaging standards. For example, there are two DICOM objects for CT image data; original (1993) and the enhanced CT object (2003) CEP08007: March 2009 Glossary 116 digital versatile disc (DVD) a type of data storage media; uses the same technology as CD-ROM but has the ability to store larger amounts of data, up to 4.7 GB per side for a single layer disc discount cash flow a technique to compare costs occurring at different times display the graphics system on a computer workstation, consisting of the hardware – card and monitor – and the software drivers. These can be classified as : primary displays performance meets the required specification for diagnostic quality image presentation secondary displays performance does not meet diagnostic criteria, but is sufficient for clinical review purposes, in support of the report or other information dose length product (DLP) a measure for approximating radiation risk calculated by multiplying the CTDIvol for a scan sequence by the length of coverage in the z axis (along the patient's length) dose profile the variation of intensity along a X-ray beam diagnostic reference levels (DRLs) indicative dose level for a given examination of patients with standard body size against which actual doses can be audited dual-energy scanning scanning the patient at two different X-ray tube energies to obtain two CT data sets EBCT electron beam computed tomography ECG electrocardiogram EBCT electron beam computed tomography ECG electrocardiogram ECRI (Emergency Care Research Institute) a US-based health services research agency effective dose representative dose measurement, giving the uniform whole body dose that is equivalent in terms of stochastic (carcinogenic) risk, to the non-uniform irradiation of various organs. Effective dose (E) is quoted in units of millisieverts (mSv) electrocardiogram (ECG) record of electrical activity in the heart over time electron beam computed tomography (EBCT) type of CT scanner that uses a rotating beam and stationary target ring in place of a rotating X-ray tube. Was previously used for specialist purposes, particularly cardiac imaging, but now mostly replaced by MSCT CEP08007: March 2009 Glossary 117 electronic patient record record containing a patient’s demographics, attendance, (EPR) diagnosis or condition, and details about the treatments and assessments undertaken. It typically covers the care provided within one institution: a trust or a primary care trust FOV field of view FWHM full width at half maximum Feldkamp reconstruction common extended parallel projection technique used for cone-beam reconstruction on MSCT scanners..Properly called the Feldkamp-Davis-Kress (FDK) algorithm. field of view (FOV) size of an area being imaged. Can be either the scanned field (SFOV) or the reconstructed field (RFOV) filter a) X-ray filter: material introduced to remove soft X-rays from the X-ray beam b) beam shaping filter or bow-tie filter: material used to shape the intensity of the x ray beam to suit the subject c) reconstruction filter: mathematical kernel used during the reconstruction process to modify responses at different spatial frequencies flying focal spot a technique that moves the focal spot on the X-ray tube between two positions in order to improve spatial resolution focal spot the point in the X-ray tube where the X-rays originate full width at half maximum method for characterising the width of the X-ray beam by measuring the distance between the points at which the intensity is 50% of the peak. GB gigabyte Gy gray gantry tilt ability to offset the gantry rotation from the couch axis. Used in head scans to avoid critical dose-sensitive organs, such as the eyes gating timing of the data capture with a physiological event, such as breathing or heart beat. This may be a) prospective : the image data is only acquired when a certain event is occurring, such as triggered by an ECG trace b) retrospective : part of the image data set is selectively chosen after acquisition according to records of the physiological event, such as breathing patterns generator produces the high voltages required for the X-ray tube CEP08007: March 2009 Glossary 118 geometric efficiency one measure of dose efficiency of the scanner, it is the ratio of the slice width imaged to the total slice width irradiated. Strictly should be the ratio of dose used to create images to total dose gray (Gy) the unit of absorbed dose grid an array of septa that are introduced to either reduce noise due to radiation scatter or (in CT) to reduce the sampling aperture and hence increase spatial resolution HRG Healthcare resource group HIS hospital information system HL7 Health Level Seven Health Level Seven (HL7) used here to refer to standards and frameworks related to healthcare interoperability , that is the transfer of data between different systems in healthcare. Properly, it is the non-profit organisation that develops such standards. Health Protection Agency (HPA) the Health Protection Agency provides an integrated approach to protecting UK public health through the provision of support and advice to the NHS, local authorities, emergency services, other Arms Length Bodies, the Department of Health and the Devolved Administrations. helical scan a CT scan where the patient is moved constantly through the rotating gantry. The X-ray beam describes a helix about the patient hospital information system (HIS) hospital wide computer system containing data such as patient details and test records, including laboratory and radiology reports. Can be all or part of electronic patient record (EPR), or patient administration system (PAS) Hounsfield Unit (HU) normalised scale of x ray attenuation used in CT scanning. It is defined by air (1000 HU) and water (zero HU). HRG v4 a set of codes used to allocate tariff payments to patient procedures, such as CT examinations IAC inner auditory canal ICT information and communication technology IEC International Electrotechnical Commission. IEE The Institution of Electrical Engineers (now IET – Institution of Engineering and Technology) IG information governance CEP08007: March 2009 Glossary 119 IHE Integrating the Healthcare Enterprise IP international protection rating or ingress protection rating IPEM Institute of Physics and Engineering in Medicine. ips images per second IR(ME)R Ionising Radiation (Medical Exposure) Regulations 2000 IRR Ionising Radiation Regulations 1999 ImPACT (Imaging Performance Assessment of CT scanners) An independent provider of evidence supporting the purchase of CT scanners in the UK, funded by the NHS Purchasing and Supply Agency’s Centre for Evidence-based Purchasing Institute for Physics and professional body for those involved in medical physics and Engineering in Medicine clinical engineering. Operates a special interest group in (IPEM) diagnostic imaging. Publishes guidance for the use and routine testing of equipment Integrating the Healthcare Enterprise (IHE) global initiative designed to advance the state of data integration in healthcare across all hospital systems. Establishes common functional profiles The Ionising Radiation (Medical Exposure) Regulations 2000 (IR(ME)R 2000) British national regulations that relate to the safe operation of X-ray equipment in terms of patient safety The Ionising Radiations Regulations 1999 (IRR 99) British national regulations that relate to the safe installation and operation of X-ray equipment in terms of staff and public protection IP code (or IPxy) system to rate the protection provided against the intrusion of, dust, and water in electrical enclosures isocentre the point around which the CT system rotates. Also the visual centre of the reconstructed image isotropic resolution CT images where the resolution in the scan plane and along the scan axis are the same kHU kiloheat-units kV kilovolt kVA kilovolt-amp kW kilowatt kWh kilowatt-hour CEP08007: March 2009 Glossary 120 LAN local area network LCD liquid crystal display LED light emitting diode lp/cm line pairs per centimetre LR legitimate relationship mA milliamp mAs milliamp-seconds MDD medical device directive MDR medical device regulations mGy milligray MHRA Medicines and Healthcare Products Regulatory Agency MHU mega heat units minIP minimum intensity projection. MIP maximum intensity projection. MOD magneto-optical disc MPE medical physics expert MPR multiplanar reformat MSCT multi-slice computed tomography mSv millisievert MTF modulation transfer function magneto optical disc (MOD) a type of data storage media; 5 ¼” disc cartridge that stores up to 786 MB, can be re written and used many times market forces factor (MFF) an agreed premium percentage rate added to PbR tariffs to account for local circumstances. maximum intensity projection (MIP) pseudo-3D system for viewing volumes of data, where the CT number of each pixel is given by the highest CT number of a voxel on a path traced through the volume miniPACS modality-specific PACS. Sometimes with specialist features optimised for one study or image type that cannot easily be integrated in a PACS that covers a wider remit. May also refer to specialist department systems, such as in A&E minimum intensity projection (minIP or mIP) like a MIP, but using the lowest CT number instead of the highest CEP08007: March 2009 Glossary 121 modality worklist list of requested and scheduled patient studies sent to and displayed at the appropriate acquisition modality. Data originate in the RIS, but may be brokered through the PACS to the modality modulation transfer function (MTF) a description of the ability of imaging equipment to reproduce spatial detail of an object in an image multi-slice computed tomography (MSCT) CT performed with more than one row (or bank) of detectors along the patient's length, capable of producing more than one image simultaneously. Also called multidetector CT (MDCT), multichannel CT (MCCT) or multirow CT (MRCT) multiplanar reformat slice images created from an existing set of image data. Can be at a different thickness, aligned to another plane, or based along a curved path multisector reconstruction method of building up cardiac images from data gathered from many scan rotations NHS National Health Service. NHS PASA NHS Purchasing and Supply Agency. NICE National Institute for Health and Clinical Excellence NHS Purchasing and Supply Agency (NHS PASA) DH funded agency supporting procurement in the NHS [http://nww.pasa.nhs.uk] NHSnet (nww) similar to the internet, but is only accessible to computers within the NHS (image) noise (random) variation of (pixel) values in an image that can interfere with contrast and detail resolution. Most apparent in regions of low signal OBS output based specification OPCS-4 Office of Population Censuses and Survey Classification of Surgical Operations and Procedures, 4th revision Official Journal of the European Union (OJEU) channel for the advertisement of public procurement projects in member states of the European Union. Invitations to express interest are published in the Supplement (OJ S) and are available electronically from the Tenders Electronic Daily website [http://ted.europa.eu] operational requirement the minimum acceptable performance for the proposed system CEP08007: March 2009 Glossary 122 Output-based specification (OBS) a document stating the objectives (outputs) the proposed system must achieve. This should focus on the ‘what’ of the operational and clinical practices, rather than ‘how’ of technical detail, which can be addressed in the statement of needs where necessary PACS picture archiving and communications system PbR payment by results PPE personal protective equipment PACS broker device that allows the PACS to interface with the hospital information system (HIS) and/or the radiology information system (RIS). This is not essential in all systems, as the RIS and HIS may be able to interface directly with the PACS using the HL7 standard partial volume effect effect that occurs when one sampled voxel contains a mixture of tissues. The resulting value is an average of all those present, which can lead to mis-labelling of the sample in some circumstances. This is related to pixel size, but is more dependent on slice thickness patient administration system (PAS); computer system for managing patient details, such as appointments, demographics etc. May be part of, or synonymous with, the HIS or EPR depending on the local context perfusion scanning use of an imaging modality to characterise perfusion (the passage of fluid through tissue). In CT this is commonly to assess brain tissue damage by assessing blood flow. picture archiving and communication system (PACS) system that manages the storage and retrieval of digital images pitch in helical scanning, the ratio between the distance moved by the patient during one gantry rotation (the table feed), and the width of the image sample being scanned (the beam collimation). power factor a measure of the efficiency with which electric power is used QA quality assurance QC quality control QC testing routine testing of the scanner as part of the QA process, that aims to ensure the scanner performance is acceptable. CEP08007: March 2009 Glossary 123 query / retrieve a DICOM service class that underpins the ability to query a device (such as a CT scanner) for a list of studies, and to allow the transfer of relevant images to another device (such as a workstation) RCR Royal College of Radiologists. RDA radiology department assistant RF radio frequency RIS radiology information system RPA radiation protection advisor RPS radiation protection supervisor RSNA Radiological Society of North America. RT radiotherapy radiology information system (RIS) a computer system which stores the appointment information for a radiology department and may be linked to the HIS. A PACS may take exam booking information and demographics from the RIS to form worklists (clinical) report contains the radiologist’s reading of the image and is part of the diagnostic procedure. All X-ray studies must, by law, be formally reported, and the report retained as part of the patient records for a minimum period. In modern departments, the report is usually recorded in the RIS. Reports may be typed, dictated or created using voice recognition systems reconstructed field of view (RFOV) size (in x-y plane) of the data set that is reconstructed to form the CT image reconstruction algorithm (filter) mathematical operation applied during the image creation that can, for example, reduce image noise or enhance edge details reconstruction matrix the array of pixels that is displayed as the CT image respiratory gating timing the image data to the breathing pattern of the patient. May be used as a trigger to ensure the scan is taken at a fixed point in the cycle rich client a computer (workstation) which does as much processing as possible and passes only data required for storage and archive to the server. (Contrast with thin client.) Also called thick or fat clients SCoR Society and College of Radiographers CEP08007: March 2009 Glossary 124 SNOMED CT Systematised Nomenclature of Medicine Clinical Terms SoN statement or summary of needs scan field of view (SFOV) size of area being imaged (scanned) in the x-y plane scan projection radiograph (SPR) initial (low dose) scan acquired using a static tube and moving bed. This is used to plan the full CT scan sequences, and may also be used for tube current modulation Sg2 an international healthcare intelligence company sievert (Sv) the unit of dose equivalence or effective dose; a measure of the potential for radiation harm single-slice rebinning (SSR) planar decomposition technique used for cone-beam reconstruction on MSCT scanners.. slip ring a means of providing cable-less connection for power and data systems . Allows the continuous rotation of the gantry spatial resolution defines the smallest feature that can be detected in an image. This is usually quoted as line pairs per cm (lp/cm) for CT scanners statement of need (SoN) a procurement document for internal use, outlining the requirements of the project. It can subsequently be developed into a more detailed statement (DSoN). More focussed on the details of how something is achieved than the output based specification (OBS) TPS (radiotherapy) treatment planning system TSO The Stationary Office teleradiology transmission of a diagnostic images from one location for review at a remote location. Most often used when transmission is beyond the hospital LAN, but also used in some circumstances to indicate sharing of image between trusts temporal resolution the minimum time frame to obtain enough data to reconstruct the image. Important in reducing motion artefacts in cardiac scanning. thin client a computer (workstation) that depends primarily on the central server for processing activities. The word "thin" refers to either the small amount of data transferred between the client and the server, or the small load required on the user’s computer. CEP08007: March 2009 Glossary 125 tube current modulation variation of tube current according to the relative attenuation of the object voice recognition (VR) a process which takes the spoken word as its input and produces text as the output. It can be used in an imaging department to aid in the production of clinical reports volume rendered image (VR) method for displaying 3D image data that assigns colours and degrees of transparency to different CT number ranges. Good for displaying overlapping structure WEEE Waste electrical and electronic equipment web browser application used to display 'thin data' (aka thin client), typically based on web protocols such as HTML. Can be used to display patient records or images in clinical environments workstation a computer running applications software. There are several types, the main ones being: a) diagnostic or reporting workstation: used for viewing images for primary diagnosis and/or production of clinical reports. A reporting workstation will commonly have multiple diagnostic (high quality) display monitors, usually 2 or 4 screens, capable of meeting specific guidelines for resolution, contrast and brightness. These may be for CT reporting only, or shared for reporting all radiology images b) PACS workstation: is able to retrieve and display image data from the PACS. These vary from simple review workstations on the wards, to diagnostic workstations with specialist reporting tools and RIS integration c) review workstation: used for checking that acquired images are of the required quality and that all necessary views have been performed. Often at least one display on the CT control console will act as a review (work)station. 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Guidance Notes for the Protection of Persons Against Ionising Radiations Arising from Medical and Dental Use London; HPA http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1195733 842609?p=11589450665166 [cited November 2008] [136] Medical Electrical Installation Guidance Notes”. (MEIGaN) and Annex, “Healthcare interpretation of IEE Guidance Note 7 (Chapter 10) September 2007. http://www.mhra.gov.uk/home/groups/commsic/documents/websiteresources/con2018069.pdf [cited November 2008] CEP08007: March 2009 References 141 [137] IEC 60364-7-710 Electrical installations of buildings Part 7-710: Requirements for special installations or locations Medical locations. http://webstore.iec.ch/webstore/webstore.nsf/artnum/029477 [cited November 2008] CEP08007: March 2009 Appendix 1: Supplier contact details 142 GE Healthcare Siemens Healthcare 352 Buckingham Avenue Slough Berks SL1 4ER Faraday House Sir William Siemens Square Frimley Camberley Surrey GU16 8QD tel: 01753 874000 website: www.gehealthcare.com tel: 01276 696000 website: www.siemens.co.uk/medical Philips Medical Systems The Observatory Castlefield Road Reigate Surrey RH2 0FY tel: 01737 230400 website: www.medical.philips.com/uk/ CEP08007: March 2009 Toshiba Medical Systems Boundary Court Gatwick Road Crawley West Sussex RH10 9AX tel: 01293 653700 website: www.toshiba-medical.co.uk Appendix 2: EU procurement procedure 143 EU procurement procedure Lease options National frameworks are in place for operating leases to help the NHS procure leases more cost efficiently and effectively. The framework came into place on 1st April 2007 and runs for two years. Further details are available from the PASA website [94]. EU procedures The Public Sector Directive (2004/18/EC) has been transposed into UK law. This has been achieved by means of the following statutory instruments: • the Public Contracts Regulations SI 2006 No.5 (the regulations) [95] • the Utilities Contracts Regulations SI 2006 No. 6 (not relevant to this guide). The regulations apply to contracts worth more than £90,319 (from January 1st 2008) [73] over their whole life, and specify the procedures to be followed for public sector contracting, including adherence to strict timetables, requirements for advertising, invitation to tender and the award of contract. Organisations undertaking a procurement exercise covered by the regulations must give all suppliers an equal opportunity to express an interest in tendering for the contract by placing a contract notice in the Official Journal of the European Union (OJEU). At all stages of the procurement process, the purchaser must be demonstrably fair, as any decision made can be challenged by the unsuccessful suppliers. Establishing a procurement strategy To achieve a successful outcome, decisions need to be made on: • • • • • • • • whether an existing contract/agreement can be used the need to consider sustainable development issues whether EU directives apply the type and form of contract sourcing potential suppliers duration of contract and opportunity to review/extend payment schedules how to minimise any risks with the chosen strategy, including supplier appraisal and evaluation/clarification of suppliers’ bids. CEP08007: March 2009 Appendix 2: EU procurement procedure 144 Preparing a business case A business case should be drafted and approved before conducting any procurement exercise. Further guidance on preparing business cases is available from the Office of Government Commerce [96] and an illustrative example is provided in the NHS PASA Operational Purchasing Procedures Manual, Procedure 1-01 [77]. The EU tendering exercise EU procurements usually take between 4 and 6 months to complete. This needs to be taken into account in the planning stages. The length of the exercise depends on the chosen procedure (open or restricted). Further information is available from the Department of Health [79]. The procurement panel A multidisciplinary team should be selected to guide the purchase. Representatives from clinical, user, technical, medical physics, estates and financial areas should be considered. Identifying potential suppliers Criteria for supplier selection must be established. A supplier pre-qualification questionnaire may be employed, as an initial screen to exclude unsuitable suppliers, which asks for details such as skills and experience of the service engineers. Evaluation criteria Performance specifications should be derived from local operational requirements, and agreed by the procurement panel. They will form the basis for assessing the adequacy of suppliers’ technical specifications, provided in response to the technical specification questionnaire. It is important to have agreed on the performance specifications of the product as they will be used in the adjudication against company specifications. Requests for features which are supplier-specific are not permitted under the regulations. Very specific features which are not supported by operational requirements are also not allowed. Award of contract Following award of the contract to the successful supplier; unsuccessful suppliers may need to be debriefed. This is at the supplier’s request. CEP08007: March 2009 Appendix 2: EU procurement procedure 145 Buyers must be aware of the ‘Alcatel’ procedure (see the Trust Operational Purchasing Procedures Manual, Procedure No.T-08, section 6 - ‘Mandatory Standstill Period’ [97]). For more information on procurement please refer to the Department of Health website [98]. CEP08007: March 2009 Appendix 3: Supporting sustainable purchasing 146 The UK Government Sustainable Development Strategy established the Sustainable Procurement Task force (SPTF) to bring about a change in public procurement. The SPTF’s National Action Plan on Sustainable Procurement sets out how this can be achieved. More information can be found on the UK Government Sustainable Development website [99]. Good procurement practice is about making decisions on the whole-life costs including social and environmental implications. Although the costs and benefits of sustainable procurement are hard to quantify, it is important to encourage manufacturers, suppliers and contractors to develop environmentally and socially preferable goods and services at a competitive price. This section provides some practical guidance on how this and other sustainability issues can be incorporated into procurement decision making processes. Selection criteria The following criteria should be applied to all purchases of equipment. Equipment should not be purchased or contracted for if it does not satisfy criteria that are required by a trust’s local policies. Primary (mandatory) criteria • The supplier must provide full details demonstrating compliance with the UK WEEE regulations (2006) [27] including producer registration, compliance scheme details, and correct product marking. Secondary (discretional) criteria These criteria are not mandatory, but may be considered as part of the procurement process: • does the equipment meet the standards required under UK Restriction of Hazardous Substances regulations (2005) [28]? (These are currently voluntary for medical equipment). • what energy efficiency features have been incorporated into the product design to reduce energy consumption? For example, standby modes for computer or X-ray hardware, efficiency improvements during exposure etc. • does the supplier have systems for reducing their environmental impact? For example do they use recycled materials in packaging and providing documentation electronically? CEP08007: March 2009 Appendix 3: Supporting sustainable purchasing 147 Energy consumption One of the most significant aspects of sustainable procurement for all diagnostic image systems is the consumption of electricity of the system. Scanners are heavy power users. The impact of this on the energy requirements of the department should be considered. The energy demand of the CT scanners varies according to the number and type of procedure performed. Changes in the scanner and related changes in the clinical workload may affect this. The energy consumption of a system should be included in the whole-life cost of the equipment if practical (see chapter on Economic considerations). It is also important to include other power consumption related to the operation of the scanner, such as chillers, air conditioning. The following model allows a method to estimate the energy cost of the scanner system. Other models are equally valid if used consistently. Energy cost model Electricity is usually charged per kilowatt-hour (kWh). A kWh unit cost must be established to enable whole life energy consumption figures to be converted into a cost and therefore factored into the whole life cost of the equipment. However, energy prices can fluctuate and may increase at a rate greater than overall inflation in the future, so care should be taken when establishing a cost per kWh and in interpreting the results of any cost calculations. Some of the important factors to consider are listed below, along with an example of a possible formula. This formula is provided as a guide only, and it is recommended that purchasers seek additional advice from local experts or NHS PASA. The radiography department or local medical physics department are likely to have details of workloads and types of procedures from radiation dose audits which may provide useful data. • the baseline energy consumption per hour for whole scanning system whilst powered up but not exposing: Eidle (kWh) • the total additional energy consumption for each procedure type above baseline consumption: E1, E2 etc. (kWh) • as a first approximation, this can be taken as the maximum power of the scanner and an average scan time • number of each type of procedure per year: N1, N2 etc • the fraction of time the system is powered up but not exposing: fidle • the baseline energy consumption per hour whilst on standby (on in out of hours mode): Estandby (kWh) • the fraction of time the equipment is ‘on standby’: fstandby CEP08007: March 2009 Appendix 3: Supporting sustainable purchasing 148 • the fraction of time the equipment is powered down: foff • the price (£) per kWh paid: P • the total number of hours in a year (taken to be 8766): H (hours). The total cost per annum, C, can then be calculated using: C = P × {( N1 E1 + N 2 E2 + ... + N m Em ) + f idle H × Eidle + f standby H × Estandby } Using recent energy cost data from your organisation will be the most accurate approach but if this is not available there are national surveys that can provide average market costs [100]. Note that energy tariffs can change by time of day and week, so some consideration of differing kWh unit costs can be factored into the calculations. CEP08007: March 2009 Appendix 4: Preparing a specification 149 Preparing a specification The following guidance is intended to supplement local procurement procedures for CT scanners. The clinical needs of the department for provision of CT services need to be determined as part of the business case, and for preparing a statement of operational requirements for inclusion in the invitation to tender. A four-step model is suggested for determining the operational requirements, and an example statement of operational requirements is included for guidance purposes. All NHS trusts and every department have individual requirements, and the following should not restrict the stating of particular needs. You may wish to change the format, or make additions. It may be used to guide local discussion, check that existing processes address procurement requirements, and to help optimise the choice of CT for your particular needs. They are taken from a number of sources and have been adapted for this report. In all cases, you are advised to check with the relevant local experts in the purchasing office, estates department, and medical physics department to ensure that all existing legal and operational requirements are addressed. Where local expertise is not available, professional bodies such as NHS PASA, RCR and IPEM should be consulted. Preparing a statement of operational requirements The following is one model that may aid in building up a picture of your clinical needs. This will then work towards the writing of the statement of operational requirements for the tender. This statement may be in the form of an output based specification (OBS) or a (summary) statement of needs (SoN). Further detail may be identified during this process, and this can be included as a technical specification or detailed statement of need (DSoN) as appropriate. The suggested steps are: • survey: take stock of current services and equipment • ‘wish list’: draw up ideas and needs for the intended services and any other issues that have been highlighted • match: compare the equipment is available against the wish list • write: produce statement of operational requirements. CEP08007: March 2009 Appendix 4: Preparing a specification 150 Step 1 Table 21 gives a set of questions to aid an initial survey of your current service provision. This is based on text originally issued as part of the NHS PASA Capital Investment Programme for CT Scanners in 2002 [81]. Table 21. Survey of current departmental services Questions Comments and hints Current CT scans In what areas do you currently use CT scans as a stage in the diagnostic pathways? Other diagnostic procedures Especially consider areas which currently use other modalities in the clinical diagnosis, but that may be equally undertaken by a CT scan? Modalities Information systems What is the current provision of imaging modalities, and are there any changes planned? What workstations and clinical applications software do you already have in the department (or requirements for such? What digital systems do you have in your department? Which of these interact with the scanner (or ideally would)? What is the patient throughput? Either patients per hour, per day or annually. Workload What are the numbers in each (major) area? Are you currently meeting any targets that apply? Working hours Are the current hours limited by staff, by patients, by other factors? What ‘out of hours’ use is made of the scanner? How do patients move through the department? Patient pathways How do these compare for in-patient and out-patients? Are there any problem areas and bottlenecks? CEP08007: March 2009 Appendix 4: Preparing a specification Questions 151 Comments and hints What are the current image / data route through the department? Data flow Are there any plans to change these for new reporting methods? Are there any problem areas and bottlenecks? Experience Training What clinical, operational and technical experience of CT do your staff have? What is the current arrangement for training? Is it effective? What are the current service and maintenance arrangements? Technical support Are there any restrictions on clinical service due to current arrangements? Are QA and other testing programmes in place and working well? Describe the essential issues and design features , for example: Scanning suite location available area access for beds etc infection control surveys radiation protection issues power provision air conditioning Step 2 The next step is to produce a ‘wish list’ for the clinical service that will be in place with the new CT scanner. This may be based on issues with the current service, or planned developments of the service. This will normally be developed in consultation with clinical directors, service managers, and such, but it is also useful to consult the daily users to highlight any bottlenecks or issue resolutions that can be written into the wish list. Table 22 gives some ideas of items that should be considered when drawing up this list. It is beneficial if requirements can be defined as, CEP08007: March 2009 Appendix 4: Preparing a specification 152 • primary: these are the elements most likely to be considered essential • secondary: these are the elements that are very desirable, but may need to be compromised • optional: items that would be very nice to have, but there is no practical impact on the clinical service Table 22. Initial requirements Topic Items to consider In what areas do you anticipate the CT scanner will contribute to your current and future clinical diagnosis? Service provision Workload Working hours What kind of imaging will you expect to do? For example will it be used for general head imaging, musculo-skeletal imaging etc? Is there a need for specialist services such as cardiac angiography, stroke assessment, or radiotherapy planning? What patient throughput do you anticipate? And what numbers (or percentage of total) for each type of examination? Do not forget to include any planned increase due to service changes or those that you would need to meet any targets. What do you anticipate to be your days and hours of working? Will these remain as they are, or will they be adjusted with the introduction of new scanners and services? What will be the patient pathway through the department? Workflow What is the required data flow for the images? With what systems will the CT scanner need to interoperate? Data management CEP08007: March 2009 What digital storage facilities to you have/need? What appropriate hard copy facilities do you have/need? How are they to be connected to both existing and future equipment? Appendix 4: Preparing a specification Topic Items to consider Service redesign Are there other changes planned for the department that will affect the workflow in the department? How will these affect the workload and interoperability? 153 If necessary, revisit the previous questions How does the existing skills mix match that which will be required? Skills gap What staff training do you anticipate? How will this be delivered? Will it be a new room, or conversion of existing room? If new (or major refurbishment), what is the proposed location and design of suite? Scanner suite When will site be ready? How will the equipment be delivered to the site? What is the access to site for engineers during the installation? What other clinical areas are adjacent or near-by? From these, you should be able to identify the functions that the new system will need to accomplish in order to fulfil the expected clinical service. This step requires a number of iterative steps where the ‘wish list’ is refined according to practical consideration, financial constraints, relative clinical priorities, and such. At the end of this, a reasonable definition of the requirement should be possible. Step 3 In step 3 the ‘wish list’ should be compared with capabilities of equipment that is available for purchase. Reference to the relevant Comparative specification reports [84] - [88], as well as the Technical considerations and Market review chapters of this buyers’ guide will help in this. CEP08007: March 2009 Appendix 4: Preparing a specification 154 Step 4 Table 23 provides a guide to areas that should be described in a statement of operational requirements. This is not exclusive or exhaustive, and other information may be added as considered appropriate for the local requirements. Table 23. Statement of operational requirements Questions Information to provide Clinical workloads State the types of scans that you expect to undertake and some general figures on workloads, patients per day or similar. Specialist investigations State any investigations that may have specific technical requirements, such as cardiac scanning, or perfusion studies. State any requirements on the scanner usability, patient throughput. Scanner requirements State if the scanner must have a planned upgrade route during service. State any physical limits such as room size, floor loading, or power that restrict the scanner choice. Workstations Clinical applications software State how many scanner workstation will be required, and where these will be located. State if any workstations are required to be shared with other scanners or modalities. State all specialist applications required to meet clinical needs, such as cardiac angiography, 3D reconstructions, MIPs. State whether these are required at specific workstations or at remote access clients. Interoperability - clinical State any existing clinical equipment that the scanner must work with, such as contrast pumps or biopsy systems. Interoperability - technical State the RIS, PACS and other systems that will interact with the CT scanner (and workstation). CEP08007: March 2009 Appendix 4: Preparing a specification Questions 155 Information to provide State if local archiving is required. State if hard copy production is required at the scanner, or elsewhere, and if laser imagers are required, or state existing imagers (number of ports available). State if the system is required to create discs of patient data for transfer or legal use. Image and data handling State key data management and transfer functionality, such as: • images / data should be transmitted automatically to the PACS • images should be printable • to what hardware the system should be networked. You may wish to state explicitly the IHE profiles and / or DICOM functionality required, or refer to a DSoN. State any physical limitations imposed by the scanner suite, such as floor loading, space available. Scanner suite State essential features of the proposed location, such as the access, neighbouring rooms, nearby equipment, etc. State the date on which the scanner suite will become available for works and installation. State what levels of technical support are required. Support State what hours of service coverage are required. State if routine maintenance ‘out of hours’ is required. State whether a turnkey solution is required. Installation and building State any additional building works that are required. State what level of continuity of clinical service is required during building works and installation. CEP08007: March 2009 Appendix 4: Preparing a specification 156 Questions Information to provide Standards State all the international, national and local standards that apply to the scanner and the associated systems. Terms and conditions Specify any standard terms and conditions that apply. Specify other applicable terms and conditions. Note: if integration or interoperability with other systems, such as RIS or PACS, is required, you may wish to state details of these systems in an appendix or similar. These can include make/model, software version, installation date, contact details of suppliers. In the ideal case, a separate specification of the connections required to interact with these systems should be obtained to pass to the prospective tenderers. You may wish to provide a more detailed breakdown of the scanner workload in a table such as Table 24. Amend categories, or name specific investigations as required. Table 24. Clinical workload breakdown (CT scanner) Current workload (number or %) Anticipated future clinical workload Head and neck Chest Abdomen and pelvis Interventional Other (eg cardiac) … etc … It is recommended that the statement of operational requirements is produced as an output based specification, in terms of what is required for each area as listed in Table 23. Any specific technical detail of how these are obtained should be provided separately. This will then allow the manufacturers to initially offer their best solution to the stated need, and can then be modified during subsequent negotiation. It should be clear in the statement which aspects of the requirements are defined as essential and which are desirable and may be compromised in order to achieve a ‘best value’ procurement. The latter can be stated as a separate list of possible variations. CEP08007: March 2009 Appendix 4: Preparing a specification 157 Principles, standards, procedures, and guidelines There are a number of international and national regulations that apply to the equipment and installation of a MSCT scanner. All four major manufactures install units worldwide and in the UK and hence should be able to show compliance with all of the mandatory regulations. It is normal to ask for copies of relevant certificates as part of the tendering process. The following are lists of some of the regulations and other documentation that may be included in an operational requirements statement. Other requirements may be added according to local procedure. Ionising radiations For current regulations relating to ionising radiation, a local expert, such as the RPA or medical physics department should be consulted. • The Ionising Radiations Regulations 1999 (IRR 99) [21] • Approved code of practice and guidance for IRR 99 [101] • The Ionising Radiation (Medical Exposures) Regulations (IR(ME)R 2000, 2006) [22], [51] • HSE employers overview of the regulatory requirements for medical exposure to ionising radiation [102] • Medical and Dental Guidance Notes [103] • PM77 [104]. Further related guidance can be found on the HSE website [105], [106]. Building and electrical requirements For regulations relating to equipment installation, and electrical safety, the estates department and medical physics department should be consulted. • Health Building Note (HBN)6 [107], [108], [109] • Swedish regulations on radiation shielding (SSI FS 1991:1) [110] • Medical Electrical Installation Guidance Notes and annexes [111],[112] • IEE Wiring Regulations [113] • IEE Guidance Note 7, Special Locations [114] • IEC 60364-7-710 (Electrical installations of buildings – Requirements for special installations or locations – Medical Locations) [115] • British, and other, standards for medical electrical equipment o general safety and performance [116] CEP08007: March 2009 Appendix 4: Preparing a specification o o o o o 158 safety of computed tomography [117] electromagnetic compatibility [118] risk management [119] high voltage plugs and sockets [120] ingress protection [121]. Medical devices The latest information regarding CE marking, the medical device directive (MDD) and medical device regulations (MDR) can be found on the MHRA website [122]. General Health and safety As well as the specific requirements for ionising radiations and related equipment, there are general health and safety considerations, and those relating to manual handling. • • • • • • The Health and Safety at Work Act 1974 [123] Management of Health & Safety at Work Regulations [124] The Health and Safety (Display Screen Equipment) Regulations 1992 [125] Manual Handling Operation Regulations 1992 [126] Guidance on the Moving and Handling of loads in the Health Service [127] The Guide to the Handling of People [128]. There are many other notes and summaries of best practice when moving patients [129]. Contact the local Manual handling team within the trust to obtain the latest guidance and any local polices. A full list of health and safety legislation can be access at the HSE website [130]. Local H&S officers should be consulted to ensure that all local requirements are addressed. Other documentation Standard documentation also exists within related purchase areas, such as ICT systems and data networking [131][132]. Although these may not be applicable en masse to the MSCT specification, there will be guidance to good principle and practice that may be included. The local ICT department should always be consulted to identify any local networking or other such requirements. There are standard terms and conditions of contract that will apply to major capital purchases such as a MSCT scanner, for example CRACOE 2005 [133]. Others may be required by local procedures [134]. The local purchase officers, NHS PASA and NHS Supply Chain should be consulted to ensure compliance. CEP08007: March 2009 Appendix 4: Preparing a specification 159 Historical documentation The following is a list of deprecated documentation that may be useful. These are no longer routinely available from the publisher; copies may still exist within local departmental holdings. These documents should not be referenced in any specification. Even though these documents, or the regulations to which they refer, may have been superseded they still contain guidance that may be useful in the purchase process. • NHS ME Guidelines HSG(91)11 - Patient Dose Reduction - Purchasing Radiology Equipment [no longer available] • Guidance Notes for the Protection of Persons Against Ionising Radiations Arising from Medical and Dental Use [135] • TRS 89: National Health Service Procurement Directorate - Technical Requirements for the Supply and Installation of Equipment for Diagnostic Imaging and Radiotherapy (superceded by MEIGaN [136]). CEP08007: March 2009 Appendix 5: Example statement of operational requirements 160 Example statement of operational requirements This statement can be used in the absence of other pro formas, and has been produced in the form of an invitation to tender (ITT). You will need to complete the specific details according to your identified clinical and technical needs, as derived from a process similar to that outlined above. You may also wish to ask for current technical specifications, in a standard format, such as the ImPACT questionnaire*. This should aid in the comparison of performance claims and detailed specialist technical features. Before using this example, you should: • decide whether an OBS (see appendix 4) approach would suit your needs better • check with local purchasing officers that it complies with local requirements • confirm the operational requirements list • familiarise yourself with current applicable legal requirements and good practice guidance. *This standard questionnaire is widely used in NHS scanner purchases. The latest revision (version 15) has been used to produce the technical specification comparison reports ([84] - [89]). An electronic copy is available from ImPACT on application. CEP08007: March 2009 Appendix 5: Example statement of operational requirements 161 OPERATIONAL REQUIREMENTS FOR CT SCANNER(S) TO BE USED WITHIN THE CT SCANNING UNIT OF………… NHS TRUST Quotations are invited for the supply of ….. CT scanner(s) with the following specification, to be used within the CT scanning unit, in....……………… NHS Trust. Please supply information about the system by answering the stated requirements. The responses should take into account the users requirements as stated in the General specification and the Specific CT scanner requirements sections below. General specification 1) Two X-ray CT scanners are required which are capable of providing Xray CT images of the highest quality and at the highest currently achievable throughput. 2) The clinical services are for a wide range of patients, including those from the following specialities: • • • • • • oncology cardiology trauma paediatrics general anaesthetic cases a wide range of other specialties from a major teaching hospital. 3) The systems must have functions and facilities to allow the fast and safe patient handling and imaging to achieve a high throughput. 4) The study image handing must be excellent to allow the rapid and accurate assessment of the diagnostic images, and the rapid and reliable transfer of study data to the local PACS system. 5) The service will cover cardiac imaging, and we expect that the coronary imaging studies will be carried out on one system. 6) The systems must be reliable, and be maintainable with the minimum of down time for calibrations and routine servicing. CEP08007: March 2009 Appendix 5: Example statement of operational requirements 162 7) The device must conform to all appropriate UK or international standards (including part 2 and 3 standards where applicable) for the manufacture of medical devices, and be CE marked. (Please provide copies of certificates issued by your Notified Body which are applicable to the design and manufacture of this equipment). 8) Please specify the expected life cycle of this type of equipment. 9) Please specify the time required between placing an order and delivery of the equipment. 10) Please specify the estimated time required for installation and commissioning. 11) Please specify whether your company operates an out of hours telephone helpline available to users of the equipment to contact for advice. If so please state its hours of operation. Conformance requirements for X-ray generating equipment 12) All items included in the tenders must comply with current standards, regulations and guidance. Details of conformance should be listed. The following areas must be considered: • • • • ionising radiation; public, patients and staff medical equipment safety building requirements electrical safety 13) Confirmation must be given that equipment offered is CE-marked and conforms to regulations regarding medical devices. 14) All equipment supplied must be user friendly, with clear identification of all controls, which are to be marked with standard IEC symbols. Safe use of computers and display screen equipment should be considered. 15) During radiological examinations, movement of both the patient and equipment is often undertaken. Managers should be aware of Health and Safety legislation (Health and Safety at Work Act 1974) with regard to manual handling and their responsibility to provide equipment that minimises the risk of injury to staff. CEP08007: March 2009 Appendix 5: Example statement of operational requirements 163 16) Where the equipment contains critical components (eg monitors, image intensifiers, direct digital detectors) which have a limited life, the duration shall be specified in the quotation, and an indication of the cost of replacement given. 17) Where any parts of the solution are based on PCs or other computer equipment, the support and maintenance for this equipment shall be explicitly stated. 18) The equipment must be designed and constructed to facilitate effective cleaning and disinfection after use. Detailed instructions must be given in the operator's instructions, for cleaning and disinfection of all items of equipment that may come into contact with bodily fluids. The materials to be used should be specified. 19) For fixed installations, the installer is responsible for a critical examination of the X-ray unit. Although the installer must consult a radiation protection adviser (RPA), either appointed by the Trust or the installer, the RPA does not need to be present for the critical examination if this is unnecessary. Final acceptance will be subject to a satisfactory report by the RPA. 20) The equipment suppler shall perform tests and visits as are necessary to ensure that there is sufficient access to the proposed equipment site for the delivery of the units, and any installation works. 21) The equipment supplier shall perform such tests as are necessary to ensure that the proposed installation will function correctly from the mains supply which is available in the room in which it is to be installed. Specific CT scanner requirements The systems must be able to perform the following applications. Please provide information on the operation, performance and radiation dose characteristics of the system in performing these applications. 22) CT perfusion imaging studies. Please include information on how this is performed CEP08007: March 2009 Appendix 5: Example statement of operational requirements 164 23) CT angiography, for example for pulmonary studies, within a breath hold 24) Cardiac imaging as appropriate for imaging the coronary vessels, with a high temporal resolution, high spatial resolution with low motion blurring, and with as low a radiation dose as possible. Please state a. whether both prospective and retrospective ECG gating possible? b. the range of rotation times that can be used in ECG gated cardiac imaging c. the number of phases that may be used in gated cardiac imaging, and the corresponding acquisition arc for data collection d. provide information on the radiation dose delivered during different cardiac imaging procedures (eg CTDI as a function of the number of phases), with typical exposure factors recommended for a 70 kg male patient e. the system must have excellent facilities for data handling, data editing and display. 25) Virtual bronchoscopy and colonoscopy. Desirable features 26) The following features are regarded as highly desirable, please specify whether the system incorporates these or include cost if these are available as an option. i. xxxxxxx ii. yyyyyyy Consumables and accessories 27) Please include a comprehensive list of consumables and accessories designed for use with this device together with its cost. Please give an estimated cost of running the system per patient day. 28) As a minimum, the following accessories and the cost should be included within the tender: CEP08007: March 2009 Appendix 5: Example statement of operational requirements 165 a. two twin barrel injection pumps for angiographic, perfusion and coronary work b. an ECG monitor and leads for use in ECG gated cardiac imaging c. one / two workstations capable of handling the full range of applications on the system d. any other accessories that are required for the correct operation of the scanners. Cleaning of the device 29) The device must be able to be cleaned using materials and detergents commonly available within a hospital environment. 30) Please provide a list of approved detergents suitable for cleaning the casing of the device. 31) Please provide a copy of your recommended cleaning instructions, please specify techniques which are known to damage the casing and internal components of the device. 32) Ensure that the relevant decontamination/reprocessing section is completed in the June 2003 version of the Pre Purchase Questionnaire which must be submitted with your quotation. 33) The systems must be able to be powered by the mains supply, and the manufacturer must make inquiries to ensure that the supply meets the needs of the system. 34) Does the system need external water cooling? Please state all of the environmental requirements (temperature, humidity, power rating etc). Other features 35) Please specify all other features of the device not requested in this product specification and describe how this improves patient safety or benefits the patient. 36) Please specify the dimensions and weight of the device, include values for external power supply units. CEP08007: March 2009 Appendix 5: Example statement of operational requirements 166 37) Please provide details of the equipment's protection against fluid ingress, ie IPxy rating, as set out in standards such as lEC 60529. Maintenance 38) In order to ensure the equipment is maintained in proper working order the basic maintenance requirements are as follows: a. engineer call-out response time of XXXXX hours b. appropriate Annual preventative planned maintenance programme please describe the expected programme c. appropriate annual validation (calibration and additional parts/components) - please describe the annual procedure programme d. suppliers are required to specify the services they will provide at their cost. 39) Please provide a list of parts that are required to be replaced regularly as part of routine maintenance (eg X-ray tube). Please specify the interval and current cost of replacement parts. 40) Please specify the number of trained engineers competent with this type of equipment who serve the ………… territory. 41) Please indicate any cost reduction to annual service charges if Medical Physics engineers are trained in first line support, or in full maintenance procedures for the system. Training 42) In line with clinical governance issues around the use of equipment it is essential all staff using and supporting the use of the device are appropriately trained. 43) Training requirements are: a. user training for all staff within the trust who would be expected to use this device as part of their routine duties. This currently includes approximately xxx radiographers CEP08007: March 2009 Appendix 5: Example statement of operational requirements 167 b. ongoing regular applications training of trust staff c. further support and advice throughout the life of the device as required. Notes 44) Evaluation of the proposed systems will be possible during the tender evaluation phase, with the approval of the Procurement department. 45) The device supplied must be of sound construction, fit for the purpose, comply with all relevant safety and construction standards for medical equipment, and be CE marked. A PPQ form (June 2003 version) will need to be completed and presented prior to an order being confirmed; ideally this should be submitted at the same time as your tender. 46) Preference will be given to devices that are reliable, are easy to use, have the appropriate degree of flexibility and versatility, and are easy to keep clean and maintain. 47) The final choice of device will depend not only on meeting this specification but also on user preference. Trials of suitable equipment may be necessary before a final decision is made. Users will assess the various features of any equipment on trial. 48) The likely full cost of a standard procedure must be estimated, including the cost of kits of all disposable parts, fluids, etc. 49) All instructions for the use, cleaning and maintenance must be included with the quotation. The costs of any repair and maintenance contracts that are available should also be stated, together with the typical costs of major repairs if these are not included in standard maintenance contracts. 50) Any training provided, including any courses offered/recommended by the manufacturer/supplier should be stated together with any costs that may be incurred. 51) In presenting a quotation, the supplier must fully specify the device that will be provided, and clearly identify where this does not meet the requirements cited in this document. CEP08007: March 2009 Appendix 5: Example statement of operational requirements 168 52) The offered price, excluding VAT, should include any discounts or special offers available, but should however be detailed separately. The terms of the warranty must be stated. If applicable, ex-demonstration units available at this time can also be shown, with offer prices, and provided that the same guarantee terms and conditions apply as if the device(s) were new. 53) All enquires concerning this specification should be addressed to ………………………………………….. . 54) A copy of this operational requirement specification, and other related documents, are available electronically ain Microsoft Office Word format (version 2003) from ……………………………… to assist you in presenting your responses to our requirements. This will help us in matching your responses to our requirements when assessing and evaluating the tenders. 55) During the duration of the tender process you must not contact any member of Trust staff associated with this tender with the exception of staff in the Procurement department. Failure to comply with this requirement may exclude your submission during the assessment and evaluation stages. CEP08007: March 2009 Appendix 6: Site visits 169 Purpose of a site visit During the tendering phase of a purchase, the manufacturers will invite the trust to attend a site visit. Normally, the site chosen will be a leading user of that manufacturer’s equipment. For the manufacturer, it is a chance to show the scanner in operation. For the purchasers the site visit is an opportunity to validate in concrete examples the operational performance of the scanner in a clinical context similar to that where the purchased scanner will be used. A site visit is not a technical demonstration of all the facilities of the scanner. It is a chance to see the scanner operating in a clinical context. It may also be that the scanner you visit is not the same specification as that in the tender. It is important to liaise with the company representative to establish before the visit what capabilities of the scanner are included in tender. During the site visit the purchasing team should evaluate the objective and subjective elements of scanner performance, and gather the experience of existing operators of the scanner – both good and bad. This relates both to the technical performance of the scanner and the operational issues relating to its usage. It may be that as a result of a site visit, plans for clinical services, workflow design and such may need to be re-assessed. Each site visit should be consistent, factual and unbiased. A protocol should be drawn up to ensure that site visits focus on the issues of greatest importance to the department, and are demonstrably fair to suppliers. Questions asked should be related to the purchasing decision and must be reasonable. It is acceptable to request that the manufacturer’s representatives allow some time for private discussions between the staff of the host institution and the visitors. Suggested scope of site visit Although every purchasing exercise will have its own priorities, drivers and focuses, the areas to be covered can generally be divided into the categories listed below: • • • • • • • general scanning performance operational aspects clinical applications software image quality and dose installation reliability and servicing. CEP08007: March 2009 Appendix 6: Site visits 170 Some suggested questions and factors to observe for each category are provided at the end of this section. The answers to the questions may be obtained by observation and/or interrogation. Organising the site visit Choosing the site Generally the site will be determined by the manufacturer, however, it should ideally be in the UK so that the scanner is observed in a clinical context similar to the one in which it is to be used. The site chosen should be undertaking scans in the major clinical areas of interest to the purchasing team. It may be necessary to visit a second site to observe particular features of the scanner. Who to involve Ideally the site visit team should include the key members of the purchasing team and whenever possible the same team members should visit every scanner being considered for purchase. However, not every department needs to be represented on the visit team, provided the questions that are included in the visit brief are sufficient to address their needs. The team may include: • • • • • lead radiologist superintendent radiographer business manager physicist other radiologists representing a range of clinical specialties of interest, eg cardiology, paediatrics, oncology, gastro-intestinal, pulmonary. One of the team members should be assigned the responsibility of organising the site visits. Their role will include: • • • • • liaising with the manufacturers to arrange dates and venues of site visits liaising with staff to ensure availability co-ordinating the visit brief assigning tasks to individual team members collating notes and scores from each site visit. Preparation • Prepare a visit brief – a list of key goals for the visit, ‘must ask’ questions and tests, additional questions, team responsibilities, scoring sheets and guides CEP08007: March 2009 Appendix 6: Site visits 171 • check for any known issues for that scanner – or even rumours that can be addressed at the time • establish the questions to be asked at the visit and scoring system to be used • each team member should have a set of questions they need to address and these should be covered on each site visit • ensure that specialist scans of interest, eg cardiac, will be performed on the day of the visit • ensure that appropriately qualified personnel, both from the manufacturer and the host institution will be available for discussions/questions during the site visit. What to do on a site visit The visit should start with introductions of the visiting purchase team and an outline of their goals for the day. Each team member should spend time with their counterparts at the visiting site and cover the questions in their brief. If possible make notes during the site visit or as soon as possible after. Clinical images obtained for standard-sized patients should be viewed for a range of examinations of interest. Note scan parameters and dose values for these images and request copies of this data on a disc for subsequent review. In addition it is particularly recommended that the radiographer on the team requests some ‘hands-on’ experience on the scanner. It is easy on such visits to be distracted by some additional features and information that “crops up”. One member of the team should ensure that all the mandatory questions and assessments are addressed. If necessary, any issues arising should be recorded and included in visit notes; these can then be followed up subsequently with the manufacturer’s representative. What to do following a site visit It is essential that a site visit is properly recorded. Notes and scores from the visit should be placed on record as soon after the event as possible. If it is necessary that other people attend the next site visit they may need to refer to these visit notes in order to ensure that a consistent approach is maintained. The notes and scores may be used to decide between tenders and so should be treated as important records; it may also be necessary to use them as part of the debriefing to the failed bidders. CEP08007: March 2009 Appendix 6: Site visits 172 Suggested questions and features to observe The following is a list of suggested questions and features to observe. It is not intended to be prescriptive nor exhaustive. General Ask about the general operation and installation of the scanner: do people like it is it ‘user-friendly?’ has it been reliable? what features and functions have they found most / least useful? what scans are carried out? if not all the scans you are considering are done at this centre, what are their reasons – are they related to the scanner at all? • were any unforeseen problems encountered during purchase or installation? • have any particular problems been encountered with the operation of the scanner? • • • • • • Scanning performance Observe some scans being set up. The radiographer in the team should also ask to operate the scanner so as to make ‘hands-on’ assessment of its user-friendliness and ergonomics. Note the following: • • • • • ease with which a patient can be placed and orientated on the scanner ease with which the scan is selected and planned how intuitive is the scanning software? how quickly the images are available from the ‘scan button’ being hit? the quality of the images and other information presented to the operator. As it will not be possible to observe the full range of clinical examinations further questions should be asked relating to the scanning performance: • have any problems been encountered with setting up of patients for any particular examinations? • how easily can an operator amend scan parameters? • can protocols be made ‘tamper-proof’? Operational Scanning workflow • Is the scanning workflow satisfactory? CEP08007: March 2009 Appendix 6: Site visits 173 did workflow require any modification to accommodate scanner? do users have any recommendations that could improve this? time taken for start-up satisfactory? time taken and frequency of routine calibrations satisfactory? time taken for daily qc satisfactory? scanner couch/gantry controls satisfactory? setting up patients satisfactory? image reconstruction time satisfactory? (if possible make an objective assessment of this by setting up a scan with a given number of reconstructed images and measuring the time taken from the start of the scan to the appearance of the final image, for at least two specific examinations, eg standard brain and standard abdomen scan.) • have there been any tube cooling issues? • • • • • • • • Reporting workflow • What are the reporting patterns, eg on console, on workstation, on PACS, remotely? • what standard post-processing, eg MPRS, can be integrated into protocols? • what are the post-processing patterns, ie where is it done and by whom? • is the post-processing and reporting workflow satisfactory? • do the users have any recommendations that could improve this? • are there any data transfer issues? • is speed of data transfer satisfactory? • were any changes required to the network or data servers due to the CT workload? Training • • • • Was training provided by manufacturer adequate? what areas required most training? what training model was used? Was everyone trained or was it cascaded? what level of on-going training is provided? Installation Assess the scanner suite in terms of whether the space is adequate and how it compares with the area available at your site: • is there any additional plant located outside the scanner suite? • were there been any issues with the availability of the scanner for delivery? • were there any problems during the purchase, eg additional items having to be purchased? CEP08007: March 2009 Appendix 6: Site visits 174 • were there any problems during the installation, eg unanticipated infrastructure requirements? Clinical applications software Assessment of the clinical applications software may be part of the site visit, but often the manufacturer will make a separate arrangement for this, as it may require a full day for all interested parties to evaluate this. Ideally the manufacturer will bring the workstation to your hospital site. The assessment will generally start with a general demonstration of the software by the applications specialist. Opportunity should then be given for all interested parties to get some ‘hands-on’ experience. Each radiologist should select some clinical applications of interest and run through the same ones on every manufacturer’s system. Make a note of the following: • • • • • length of time taken to perform post-processing any desired features not available particular features liked image quality score user-friendliness score. Image quality and dose Ask to see some clinical examples of images that are similar to those that you will be acquiring in your clinical context. The images viewed must be for standard-sized patients, otherwise dose comparisons will not be valid. If you are contemplating an expansion of service into another area of scanning, try to view some images to assess the potential of the system for your future needs. For each set of images viewed tasks note the following: • scan parameters, particularly imaged slice thickness • window width and level used (if possible use similar settings to view images on each site visit) • image quality score • spatial resolution • contrast resolution • artefacts • associated radiation dose as given by CTDIVOL and DLP. CEP08007: March 2009 Appendix 6: Site visits 175 You may wish to perform a more objective assessment of image quality using CT performance phantoms. It is unlikely there will be sufficient time for this during the site visit, so the physicist on the team may wish to make separate arrangements. Reliability & servicing Have any clinical issues arisen as a result of scanner problems? have there been any problems with the availability of parts if required? what is the tube replacement option? what options were chosen for engineer support (and reasoning)? have engineer call-out times been satisfactory? has adequate support in terms of advice on any problems encountered been satisfactory? • is the servicing carried out as was specified in the service contract? • • • • • • Scoring metrics The site visit is one means of obtaining information for the evaluation process used for scanner selection. However, each aspect assessed in the site visit should also be scored. An example scoring scheme may be of the nature: 1) 2) 3) 4) unacceptable not ideal, but could be used clinically meets our basic requirements exceeds requirements. It is important to note that in such a scheme, a score of 3 or 4 is acceptable. A score of 2 indicates that it would be possible to use the scanner if this is a minor feature. CEP08007: March 2009 Appendix 7: Evaluation scoring 176 Evaluation scoring This scoring mechanism is a suggested method of determining your order of preference, and is not obligatory, but will help make the selection process more objective and help in the debriefing process to unsuccessful tenderers. You will need to establish the scoring and weighting system. Scoring should be on a scale (such as from 1 to 10) comparing each model to some base level of acceptability, and not against each other model. It is useful include a brief description of your scoring methodology, ideally with concrete benchmark examples for each score. You will need to determine the weighting given to each criterion; this will be dependent on your own local circumstances. The weightings should sum to 100. The total for each topic is achieved by multiplying the score by the weighting. These are then summed to give a total mark for the scanner being evaluated. Scoring criteria and weightings should be the same for all scanners Possible options are: • each department has its own weighting based on their perception of the relative importance of each topic • weightings are agreed as a whole by the evaluation team • weightings are agreed in advance and kept ‘secret’ from those undertaking scoring. There are many other options possible. Please consult with the local Procurement officer to ensure that local requirements are met. For each scanner system being evaluated, team member should consider the performance of the scanner in a number of topic areas. Table 25 below gives some examples and items that should be considered in each area. These can be modified or added to according to local needs. Team members should then score each topic according to the stated and agreed criteria. You should provide an explanation of your reasoning behind each score, ie the advantages and disadvantages each element that you evaluated. CEP08007: March 2009 Appendix 7: Evaluation scoring 177 Table 25. Clinical and technical evaluation score sheet template Company and model: Topic Items to consider Scanner Dimensions and weight Ancillary plant Gantry aperture Patient friendliness Generator power X-ray tube Rotation time Detector array Image quality Radiation dose CEP08007: March 2009 Sites and dates of assessment visits: Advantages Disadvantages Weight Score Total Appendix 7: Evaluation scoring Topic Items to consider Patient couch Patient handling Couch controls Dimensions Couch movement Patient comfort Positioning accessories Ease of cleaning Operator console Dimensions Ergonomics layout user-interface User friendliness scan set-up protocol set-up data management Software options included Diagnostic workstation User friendliness Functionality Connectivity Software options included CEP08007: March 2009 178 Advantages Disadvantages Weight Score Total Appendix 7: Evaluation scoring Topic Items to consider Workflow Reconstruction speed Ease of data transfer Speed of data transfer Post–processing options in protocols Integration with HIS/RIS/PACS Software Post processing options Applications available Applications included in package Licensing models Data storage Hard disc capacity Optical disc options Networking and connectivity Transfer of data Compatibility with existing modalities and HIS/RIS/PACS IHE and DICOM conformance Teleradiology links Support Maintenance Tube replacement Call out / remote support Cost of parts Routine servicing Training provision CEP08007: March 2009 179 Advantages Disadvantages Weight Score Total Appendix 7: Evaluation scoring Topic Items to consider Company Sales approach Reliability Research / product development Reference site opportunities Installation Works required Provision of replacement service Disruption of other services 180 Advantages This schema has been adapted from CIP documentation [81]. CEP08007: March 2009 Disadvantages Weight Score Total Author and report details Buyers’ guide: Multi-slice CT scanners The ImPACT Group St George’s Healthcare Trust (Medical Physics Department) Bence Jones Offices Perimeter Road Tooting London UK SW17 0QT Tel: +44 (0)20 8725 3366 www.impactscan.org About CEP The Centre for Evidence-based Purchasing (CEP) is part of the Policy and Innovation Directorate of the NHS Purchasing and Supply Agency. We underpin purchasing decisions by providing objective evidence to support the uptake of useful, safe and innovative products and related procedures in health and social care. We are here to help you make informed purchasing decisions by gathering evidence globally to support the use of innovative technologies, assess value and cost effectiveness of products, and develop nationally agreed protocols. CEP08007: March 2009 181 Sign up to our email alert service All our publications since 2002 are available in full colour to download from our website. To sign up to our email alert service and receive new publications straight to your mailbox contact: Centre for Evidence-based Purchasing Room 152C Skipton House 80 London Road SE1 6HL Tel: 020 7972 6080 Fax: 020 7975 5795 Email: [email protected] www.pasa.nhs.uk/cep © Crown Copyright 2009