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NEWS BRIEF Somatom Definition Flash computed tomography scanner for cardiac and other imaging March 2010 The Somatom Definition Flash produced by Siemens Healthcare is a type of computed tomography (CT) scanner comprising of a pair of sources and detectors that move around the patient in complementary spirals. It captures information more rapidly and with lower radiation exposure than a conventional single source/ detector computed tomography scanner. The Somatom Definition Flash Scanner can be used to undertake imaging in those who cannot lie still for prolonged periods or who find it difficult to hold their breath. It also provides rapid and relatively low dose coronary artery imaging, cardiac stress perfusion scans and whole brain perfusion imaging. © Siemens Healthcare Background In conventional computed tomography a single X-ray source and detector move slowly down and around the patient to obtain overlapping images that are joined together and used in the diagnosis of a wide range of medical conditions. In 2009-10, 3.7 million computed tomography scans were performed in the National Health Service1. Current Practice This news brief is based on information available at the time of research and a limited literature search. It is not intended to be a definitive statement on the safety, efficacy or effectiveness of the health technology covered and should not be used for commercial purposes or commissioning without additional information. For a person to have a successful conventional computed tomography scan they may have to lie still for around 20 minutes and patients, such as children, who find this difficult may have to be sedated. Where moving structures such as the heart or chest are being scanned, patients will need to be able to reliably hold their breath for a short while. This can be difficult for some people, and drugs may have to given to slow down the heart. New Technology In contrast to the conventional single source computed tomography scanners the Somatom Definition Flash computed tomography scanner consists of a pair of X-ray sources and detectors. These are rotated around the patient in complementary spirals and the overlapping images overlaid to produce the final x-ray image of the patient. The company states that the scanner can produce an image more rapidly than conventional computed tomography techniques (4 seconds for a full body scan, under 1 second for a chest scan) and high quality images can be obtained with around half the radiation dose of conventional computed tomography2. By rapidly producing high quality scans with a significantly reduced radiation exposure, Siemens Healthcare believe that their Somatom Definition Flash scanner will extend the role of computed tomography to patient groups who are unsuitable for conventional computed tomography. With a rapid scan time those who find lying still difficult may be able to be scanned without sedation, drugs to slow the heart would be less likely to be needed and breath holding would no longer be mandatory 3. 1 With its rapid action Siemens Healthcare believe that their Somatom Definition Flash scanner could take the place of other more invasive diagnostic techniques such as coronary catheterisation and single photon emission computed tomography (SPECT), cardiac stress perfusion tests, whole brain perfusion imaging and full body scanning for trauma patients. The Somatom Definition Flash scanner was CE marked in December 2009. As of the first quarter of 2010 there were five scanners in clinical use in the United Kingdom with a further 6 installations planned. Clinical Studies and Research Questions The first clinical data for the Somatom Definition Flash scanner were presented at the European Congress of Radiology in March 20094. Several small studies of technical performance in chest and heart imaging have been conducted and are also ongoing. A study of 31 patients with acute chest pain compared the results from (a) a Somatom Definition Flash scanner scan, (b) a standard non-gated chest scan, and (c) a conventional retrospectively ECG gated ‘triple rule-out’ protocol. Reported radiation doses were (a) 4.08±0.81 milliSevert, (b)20.4±5.3 milliSeverts and (c) 4.40±0.83 milliSeverts respectively. Scan times were 0.7 seconds (±0.1) for the Somatom Definition Flash, and 15 seconds (±3) for conventional chest scans. The authors concluded that the Somatom Definition Flash scanner requires about one-fifth of the radiation dose of conventional ECG gated triple-rule-out protocols, matching that of a standard non-gated chest scan, but with a much shorter scan time (less than 1 second)5. In a conference abstract, a Somatom Definition Flash scanner was reported to produce a scan of the whole heart in around a quarter of a second with a radiation dose of approximately 0.95 milliSieverts6. A study evaluating radiation dosing performance reported that a Somatom Definition Flash scanner performed a stress perfusion test with a radiation exposure of less than 10 milliSieverts7. Potential Impact By performing more rapid scanning the Somatom Definition Flash scanner may reduce the need for drugs for sedation or slowing down the heart. As well as the potential health benefits to the individual patients this might also reduce the total time needed for scanning and recovery in hospital. The Somatom Definition Flash scanner may offer a less invasive alternative to cardiac catheterisation for diagnosing coronary artery disease which may be more acceptable to patients. It is also of benefit to the patient if radiation dosage during scanning can be reduced. Faster scanning times, as claimed by the company, may improve the experience for the patients and may increase the total number of scans that can be undertaken over a period of time. 2 References 1. Department of Health Publication Statistics Imaging and Radiodiagnostic Activity, 2009/10. http:// www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsStatistics/DH_117795 Accessed 3 December 2010. 2. Carrington C. SOMATOM Definition Flash: impressive performance. Somatom Sessions 6, May 2009. 3. Company correspondence, 21st May 2009. 4. Becker CR. SOMATOM Definition AS: one CT for all clinical needs. European Congress of Radiology. March 2009. Satellite Symposium SY17, presentation number E-50. 5. Sommer WH, Schenzle MD, Becker JC et al. Saving dose in triple-rule-out computed tomography examination using a high-pitch dual spiral technique. Investigative Radiology 2010;45(2):64-71. 6. Achenbach S, Marwan M, Ropers D et al. Sub-mSv coronary CT angiography using prospectively ECG-triggered high-pitch spiral acquisition. Fourth annual scientific meeting of the Society for Cardiovascular Computed Tomography (SCCT). July 2009. Abstract number 04. 7. Bamberg F, Nikolaou K, Becker A et al. Myocardial stress perfusion with a novel dual-source CT scanner - technical update and initial clinical experience. Imaging Decisions MRI 2009;13(2):49-51 (3). The National Institute for Health Research (NIHR) National Horizon Scanning Centre Research Programme is funded by the Department of Health. The views expressed in this publication are not necessarily those of the National Health Service, the NIHR or the Department of Health. The National Horizon Scanning Centre, University of Birmingham, United Kingdom [email protected] www.haps.bham.ac.uk/publichealth/horizon 3