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White Paper Top Ten Issues and Best Practices Improving Medical Imaging Display Per formance By David So re n s e n Director of Engineering/Prod Development/Sourcing Ca nvy s - Vis ual Technolog y S olu ti ons Today, LCD-based displays are more stable than ever, and many issues and artifacts relating specifically to CRT monitors have been resolved. The useful life of these displays is longer resulting in longer warranties from the manufacturers. However, the relative stability of the displays gives rise to some false premises and confidences ... White Paper Im provin g M e d ica l I m a g i n g D i s p l a y Pe r forma nce T op T en Issues a n d Best Pr a ct ice s Objective world class health care facilities, large The objective of this paper is to cite common issues, clarify misconceptions and to offer solutions, via best practices, to those who are tasked with maintaining display quality and conformance in medical imaging environments. The experts at Canvys believe that the medical diagnostic community should strive to maintain the highest quality of diagnostic and clinical displays with the goal of promoting positive patient outcomes. If the information in this paper helps solve one or two current issues the reader is experiencing, we believe our goal will have been accomplished. first-hand experiences, formal education and training along with their “view from the trenches” - crawling under, around and behind desks and dismantling and cleaning workstations - has revealed some interesting perspectives and that eye-opening most healthcare medical LCDs are not exposed to. experiences have provided These insight into display quality, wear and tear, set up, and calibration and maintenance procedures. the best practices to overcome them. an organization of display and supplied thousands of medical displays to healthcare providers and manufacturers of healthcare equipment throughout North America and Europe including products variety of manufacturers of displays, work stations, graphics cards, and software. — Dedicated field engineers and technical services team members support, maintain and — Their The outcome is a list of top ten issues and solutions technology experts, has installed a community hospitals. — Background from mid-sized hospitals and clinics, and small professionals on the viewing side of a — Canvys, multi-site institutions, teaching hospitals, calibrate displays from multiple manufacturers in all kinds of institutions: Diagnostic Displays For our purposes, we define medical imaging LCDs as those displays that are used to view medical images in a diagnostic or clinical environment. These diagnostic displays are typically arranged in PACS (Picture Archiving Communication System) workstation connected directly to configurations, medical imaging equipment for image quality control or are integrated into complete medical imaging systems. These displays can be located in A Division of Richardson Electronics | www.canvys.com | 888.735.7373 2 White Paper a variety of places within a healthcare facility including radiology reading rooms, operating rooms, cath labs, ICUs, etc. than ever, and many issues and artifacts relating specifically to CRT monitors have displays is warranties However, The useful life of these longer from the resulting the relative in longer manufacturers. stability Below are the top 10 issues affecting Medical Imaging LCDs and best practices to Today, LCD-based displays are more stable been resolved. The List of the displays gives rise to some false premises and confidences such as: address them. Most issues are surprisingly simple and are a result of limited resources (impacted by the current challenging economy) or purely inexperience and/or lack of basic knowledge about medical imaging displays. The issues listed can be commonly found at small practices as well as world class multi facility institutions. The items on the list primarily relate to the set up or maintenance of the display, work- “We can just hook them up and start using them...” Yes it is possible, but generally one should follow set up procedures to insure proper calibration. station, graphics cards, drivers and proper calibration of displays. #10 (Workstation) Incorrect setup of display resolution and/or color bit depth. “These are LCD monitors; they don’t For best image quality, the display need any maintenance...” resolution called out by the operating The maintenance is not as demanding as system on the workstation should match CRT displays, but there is maintenance to the native resolution of the display. be done. • 1600 x 1200, then the display resolution “If they go bad we can just throw them should be set up to 1600 x 1200—peri- out and purchase new ones...” Medical imaging displays allowed to bad” “go should rather not they od. be need If the native resolution of the display is • Displays are tolerant to accepting other calibration and maintenance in order to non-native resolutions, but if this is insure the best patient care possible. Poorly done interpolation is required to fill in or performing displays may result in misdiag- toss away the extra pixels and can nosis or comprised medical care. Further- cause less than optimal image quality. more improper disposal has environmental impacts that could be costly in some states. • Similarly, the color bit depth (8 bit, 24 bit, properly 32 bit, called capabilities of etc.) needs out to the graphics A Division of Richardson Electronics | www.canvys.com | 888.735.7373 to match be the card. 3 White Paper The wrong setting can limit the number of gray scales negatively impact displayed or performance. If Windows OS is being used you can find these settings easily under never matched at the new location. can Best Practices: a) For Display Properties/Settings. gray resolution of the to calibrate the c) Record and mark displays with their color coordinates to aid in future move- mended settings and make this a check point at the time of initial setup. b) Alternatively, contract the display ment. d) Provide the color coordinate target to the manufacturer or integrator to perform the initial setup of the display, workstation, and graphics cards. have not changed manufacture when obtaining replacement units. e) Be aware of new generation grayscale display c) Perform a periodic audit to ensure that settings software color point. native display and the manufacturer’s recom- the displays: b) For color medical displays: utilize color calibration the medical buy them in color matched pairs. Best Practices: a) Know scale technology that will enable tweaking of the color point in the field. and consider hiding the Display Properties d) Pay particular attention to any new or rogue workstations that get introduced. e) Utilize analyze a network these tool settings to on view and deployed workstations from a remote site. management controls to prolong LCD panel life. Use of DPMS (Display Power Management System) prolongs LCD panel life and reduces energy consumption. • #9 (Displays) Poor color match. The target luminance setting needed by medical imaging applications is generally higher than that of general When two or more displays are used office applications. The useful life of the side-by-side it is best if their colors and display more specifically their white points are (the ability to achieve the desired target luminance) is primarily a similar. • #8 (Workstation) Not enabling power Settings tab. function of the hours on the backlight. When this issue is seen in the field, either the displays were never properly color matched (common with commercial displays), or perhaps one of the displays was subsequently moved and • Reduced target luminance levels (due to aging ratios, digital backlights) affects driving decreases calibration levels A Division of Richardson Electronics | www.canvys.com | 888.735.7373 contrast and limits which may 4 White Paper ultimately violate guidelines governing • specific imaging procedures. • Implementation of a screen saver will usually prevent image retention, and even if a persistent image develops, it is Properly implemented power manage- usually not permanent and will go away ment controls shut down the monitor if exercised with a proper screen saver. backlight after periods of inactivity and thus extend the useful of the display. Best Practices: a) Setup Best Practices: a) Setup all new workstations organizational-acceptable with default from disabling with an moving image, screen saver to kick in. b) Perform periodic audits of workstations to ensure screen saver settings are the monitor will shut down. users workstations agreed upon time with an appropriate, set- ting for medical imaging displays for the b) Prevent new acceptable default setting for a specific an amount of time of non-use after which all maintained. power management settings by policy or by #6 (Graphics card) Poorly performing user controls. c) Perform periodic audits of workstations (old) graphics cards and drivers. to ensure power management settings Graphics cards and driver technologies are maintained. change rapidly. Older graphics cards may cause performance issues as other parts #7 (Workstation)Not enabling a screen of the system change, evolve, and saver to minimize image burn-in/ improve. retention. • More video RAM on the card may be LCDs can suffer from “image retention” or needed “image persistence” where the LCD systems change and a faster GPU may crystals develop memory when a static boost performance. image is displayed in one place for too long. • Task • as software or operating The graphics driver needs to be setup correctly upon initial install using the bars, icons, and other recommended driver (not a Windows static default driver). images are at risk of retaining a faint image. If the faint image is in an area • Newer drivers may be required to of the screen where medical images are support viewed, it can negatively impact image processing using the latest DirectX or quality. OpenGL new software, commands, or perform support A Division of Richardson Electronics | www.canvys.com | 888.735.7373 3D new 5 White Paper operating systems (XP to Vista to Windows 7, 32 bit to 64 bit, etc.). • • (Workstation) Poor airflow on vents Graphics cards companies continually fans are used. update their drivers, making improve- This issue can be “out of sight, out of ments and correcting bugs/issues. mind” as workstations are often Using a newer driver may solve an issue or result in better however, be careful performance; of updating positioned where they are not easily seen or cleaned. • For machines that have been deployed graphics drivers too quickly such for long periods of time, it is common to that they may be unsupported by have vent holes that are partially or the hardware or software in use on nearly completely covered up with dust the system. and lint. • Blocked vent holes limit air flow and can cause Best Practices: of both the CPU graphics card. If you are adding or upgrading workstations, it is a good overheating processor as well as the GPU chip on the a) Look for opportunities to upgrade your graphics boards. • Overheating is a potential reliability time to upgrade graphics boards. In problem that can cause loss of video, addition, if you have a major planned crashes, restarts, slow downs, or render upgrade in the workstation completely unusable. system, consider software, a or operating graphics board the graphics drivers on your deployed hardware and bring them all up to a pre-defined level. c) Communicate with your display vendor for recommended Overheating can also be a cause of poor video or video artifacts. upgrade as well. b) Audit #5 or dust/lint covering up vents where and supported updates to the graphics drivers. Best Practices: a) Schedule routine maintenance on the workstations that includes clearing and cleaning ventilation holes. b) Consider utilizing utilities that monitor GPU and CPU operating temperatures. A Division of Richardson Electronics | www.canvys.com | 888.735.7373 6 White Paper #4 (Calibration) Not taking advantage of d) Monitor the performance of the displays the functions/features available in utilizing software. outsourcing this to a third party. Quite often sites do not set-up or properly the available tools or by e) Refer to the Appendix in this paper for implement calibration and conformance recommended reference articles and software that is available from display governing standards regarding confor- vendors. mance and calibration of medical imaging displays. • Many medical grade displays come with software that not only can calibrate a • #3 display, but also include many other (Calibration) The displays are not functions and features that can provide calibrated and could or should be. feedback and help monitor, control, and There really is no excuse for using maintain deployed displays. non-calibrated displays in medical imaging Software can be set up to schedule applications. periodic conformance tests, recalibrate • Medical grade gray scale and color displays, keep white levels consistent displays across platforms, monitor temperatures calibrated and loading the calibration file (a look-up usage, and provide logs for objective evidence that the displays are typically and are have meant a to be provision for table) directly into the display. setup and performing properly. • Even most commercial color displays can be calibrated to the DICOM Gray Best Practices: a) Purchase your display hardware from a manufacturer who specializes in medical displays and offers software solutions Scale Display Function with the proper software and luminance sensor, by loading the look-up table to the graphic card or to an ICC profile. that help monitor and control performance. Best Practices: b) Consider having your display provider install the displays to ensure proper setup and implementation. c) Utilize support services for training and follow-up to ensure that the functions and features of the displays and the software are fully and properly used. a) Ensure that all displays used for diagnostic purposes are properly calibrated and that records are maintained to show calibration conformance to applicable (DICOM) standards b) It is highly recommended that displays used for clinical purposes A Division of Richardson Electronics | www.canvys.com | 888.735.7373 are also 7 White Paper calibrated to DICOM standards. (Why should a clinician substandard have images to when look it is • at Diagnostic displays need to be calibrated in order to compensate for not the necessary?) idiosyncrasies of the native luminance response of a liquid crystal display, which is particularly important c) Refer to the Appendix in this paper for recommended reference articles in and the lower level shades of gray. regarding (Failure to do so may result in the conformance and calibration of medical inability to discern a luminance differ- imaging displays. ence between pixels that have differing governing standards digital driving levels which could (worst #2 case) result in false diagnosis). (Display) Use of common commercial • color displays for diagnostic work. There needs to be enough native resolution over the face of the display to For most diagnostic work this should not properly be done – period. 5 mega-pixels for mammography). The • Commercial color displays can be used viewing angle needs to be wide enough for many clinical applications. that the gray levels and colors do not shift • with the image horizontal (typically or vertical On lower resolution modalities (ultra- movement sound or 3D reconstructed images) it is (be careful with TN type LCD panels). possible The luminance uniformity needs to be to undertake diagnostic imaging work. • show For the uniform higher resolution modalities quality of the enough does so not head that vary or the position image significantly commonly viewed by a radiologist, it is depending on image position on the inappropriate a screen. And it is helpful to minimize the violation of specifications, guidelines, noise, artifacts, and pixel defects that and laws to utilize a display with the can detract from an optimal image. and in some cases performance of a common commercial color display. Best Practices: • Diagnostic imaging displays need a minimum luminance and contrast ratio in order to have enough luminance range to assign to each digital driving level (and have enough “overhead” to have adequate life as the display ages). a) Establish and enforce a policy for the procurement of displays used in diagnostic imaging that requires them to meet minimum performance require- ments as well as all applicable specifications, guidelines, and laws. A Division of Richardson Electronics | www.canvys.com | 888.735.7373 8 White Paper b) Utilize your local medical physicist (if available) to approve the displays used in diagnostic work imaging to a) Provide easy access to approved cleaning materials for users. c) Utilize a display provider experienced in medical Best Practices: recommend b) Schedule routine cleaning by in-house or third party personnel. appropriate displays for your application d) Monitor and audit the displays used in diagnostic work to ensure no rogue displays or displays intended for other uses (navigation displays, 3D workstation displays, etc.) get used improperly. A ND NOW , AFFECTING THE DISPLAYS IS #1 THE IMAGE NUMBER QUALITY ONE ON ISSUE MEDICAL … (Display) Dirty Displays. This was by far the most common issue to be found negatively affecting medical imaging display performance. The incidence of this issue is widespread and is commonly found on displays used throughout healthcare facilities. • Dirt and dust, fingerprints, marks, food, coffee, and other sources of debris find their way on to displays and cut down on the image quality. • While it is often a function of other priorities, we have found some users are hesitant to clean an LCD because they are unsure of or don’t have access to proper cleaning materials. A Division of Richardson Electronics | www.canvys.com | 888.735.7373 9 White Paper David Sorensen was formerly the President/CEO and a principle of Image Systems Corporation. He is currently the Director of Engineering/Product Development/Sourcing for Canvys – Visual Technology Solutions and can be reached at [email protected]. Canvys is a division of Richardson Electronics, Ltd and is a provider of PACS, Surgical, and Custom display solutions for Healthcare as well as Teklink service and support. Appendix A lot of people still don’t “get” calibration with regard to medical imaging displays. “Why do we need to use a calibrated display?” “Can’t we see what we want to see on a standard display?” “Why can’t we just use a standard display out of the box?” “How does calibration work and is it really all that important?” A simple demonstration toggling the calibration on and off is often all it takes to show the difference in what can be seen in an image, especially in the low digital driving levels. It is amazing to see and hear about both clinical and diagnostic work being done on non-calibrated displays. One can view medical images on non-calibrated displays, but it is not ideal (and in some cases violates specifications, guidelines, and laws pertaining to particular areas of medical imaging). The following articles and standards will lend more insight into the critical importance of calibration of medical imaging displays and conformance to guidelines and standards. • ACR/NEMA DICOM Standard Part 3.14 Grayscale Standard Display Function • American Association of Physicists in Medicine, Task Group 18 Report (AAPM TG18) • NEMA XR23-2006 Quality Control Manual Template for Manufacturers of Hardcopy Output Devices Labeled for Final Interpretation in Full-Field Digital Mammography (FFDM) • DIN 6868-57 Deutsches Institute fur Normung-German Standard Institute. • IEC 61223-2-5 International Electrotechnical Commission • Paper: “Digital Mammography Image Quality: Image Display” - 2006 ACR by Siegel, Krupinski, Samei, Flynn et all with an excellent list of references • ACR Technical Standard for the Electronic Practice of Medical Imaging • FDA MQSA Guidelines A Division of Richardson Electronics | www.canvys.com | 888.735.7373 ©2009 Canvys | All brands and trademarks are the property of their respective owners. | EU4USv.2009/10/14 10