Guidelines for Assuring Softcopy Image Quality

Transcription

1 Guidelines for Assuring Softcopy Image Quality What s inside? Quality Control Guidelines Softcopy QA testing and frequencies Danny Deroo Product and R&D Manager QA Products

2 ABSTRACT To ensure diagnostic confidence on softcopy medical display systems, regulatory bodies in the U.S. and in Europe have defined quality guidelines for medical imaging. The AAPM TG18, DIN and EUREF guidelines outline acceptance testing, which checks whether the display solution meets the requirements, as well as frequent quality control, a periodic checkup to see if the system maintains its constancy. Copyright 2006 BARCO n.v., Kortrijk, Belgium All rights reserved. No part of this publication may be reproduced in any form or by any means without written permission from Barco. Page 2 of 8

3 TABLE OF CONTENTS Quality Control Guidelines 4 AAPM TG18 4 DIN EUREF 6 Frequency of Testing 7 Documentation 7 Improved Softcopy QA Workflow 7 Tests and Frequencies on Barco Medical Displays 8 Page 3 of 8

4 QUALITY CONTROL GUIDELINES To learn more about how the various requirements can be met, please consult the respective guidelines. Meanwhile, this article will provide a brief overview of each guideline. AAPM TG18 - Description: The American Association of Physicists in Medicine Task Group 18 (AAPM TG18) provides standard guidelines to practicing medical physicists, engineers, researchers and radiologists for the performance evaluation of electronic display devices intended for medical use. It outlines both acceptance testing and quality control. Acceptance testing is required before the first use of a diagnostic imaging device, and each time after it has been repaired or replaced. Quality control specifies periodic, recurring check-ups during the use of medical devices. - Applicability: The AAPM TG18 guidelines are applicable to display devices used to display monochromatic medical images. Display devices for medical imaging are characterized as either primary or secondary. Primary display systems are those used for the interpretation of medical images. They are typically used in radiology and in certain medical specialties such as orthopedics. Secondary systems are those used for viewing medical images for purposes other than for providing a medical interpretation. - Tests, personnel and frequency: AAPM TG18 involves the use of an extended list of technical test patterns, next to four anatomical images. In addition, AAPM TG18 prescribes that these quality control procedures should be performed by individuals with appropriate technical and clinical competencies. The overall visual assessment of a display system should be performed daily by the display user. Monthly/quarterly tests include the assessment of geometric distortions, reflection, etc. Designated personnel under the supervision of a medical physicist will ensure that these individuals develop and maintain familiarity with the tests. The annual quality control tests, such as the assessment of noise and veiling glare, are to be performed by a medical physicist. Additional links: To download the AAPM online report, please visit For more information on the AAPM plug-in, please visit Page 4 of 8

5 DIN Description: This German standard describes the performance of an acceptance test to determine the quality of image display devices. DIN describes the parameters and tools to be used for acceptance testing. If the acceptance test has shown that the image display device satisfies the requirements, the reference values shall be determined for the following constancy tests. - Applicability: Compliance to this standard is mandated by law for German, Swiss and Austrian medical facilities. This standard applies for the display of monochrome images on image display devices that can display image information in the form of grayscale values on display screens (e.g. CRT monitors and flat screens). According to the intended purpose, the DIN standard classifies display devices into performance classes. Performance class 1 includes all imaging devices for the diagnosis of digital images and for which a high spatial and contrast resolution are required, whereas performance class 2 includes all image display devices for the diagnosis or viewing which are not classified in the first class. - Tests, personnel and frequency: DIN outlines a set of technical test images and one or several clinical test images that are typical for the intended application. The acceptance test is to be performed by the manufacturer or expert after the installation or modifications that can influence the image quality and determine the reference values for the constancy tests. Constancy tests include testing grayscale reproduction (daily), geometrical image properties, image stability and image artifacts (quarterly) and veil luminance and maximum contrast, and should be performed by the user. Additional links: For more information on the DIN plug-in, please visit Page 5 of 8

6 EUREF - Description: EUREF defined the requirements for an adequate screen-film imaging system in the 'European protocol for the quality control of the physical and technical aspects of mammography screening'. This protocol follows the advice of AAPM TG18 and of preliminary results of the ACRIN (American College of Radiology Imaging Network) trial for the evaluation of the display system. - Applicability: The EUREF guidelines are a work-in-progress and apply to displays used for mammography screening. For this type of application, EUREF recommends that diagnostic workstations with two large high-quality 5 megapixel monitors be used. On the acquisition unit it may be acceptable to use a display with lower specifications, depending on the tasks of the radiographer. The limiting values for the tests are often determined in function of the use of the display (primary class (diagnostic) or secondary class display device). - Tests, personnel and frequency: The tests are based on the work of AAPM TG18. The local staff can perform several measurements. The more elaborate measurements should be carried out by medical physicists, who are trained and experienced in diagnostic radiology and specifically trained in mammography QA. Geometrical distortion, contrast visibility and display artifacts should be checked daily. Ambient light, display resolution, luminance range, conformance to the DICOM GSDF and display uniformity should be evaluated at least every 6 months. For more information on this guideline, please visit Page 6 of 8

7 FREQUENCY OF TESTING Display systems need to be tested for performance on a regular basis. However, it is possible that hardware features and reproducible performance can alleviate the need for frequent testing. It is recommended that initial testing be performed more frequently and an assessment be made on the results. If stability is maintained, it can be considered to decrease the frequency of testing, based on validated results and in accordance with local regulations. DOCUMENTATION As described in the DIN guidelines, we suggest documenting the performance criteria of each display system. In this way, the properties and behavior of the display device - to the extent that these have an influence on the diagnostic image quality - can be monitored. IMPROVED SOFTCOPY QA WORKFLOW Although quality control is often considered a major technical challenge, a lot of tools are available today to make the workflow of radiology managers and administrators easier and less time consuming. To assist administrators in their efforts to make display systems comply with the most recent regulations, Barco has developed dedicated plug-ins to be incorporated into its MEDICAL softcopy QA software. With these plug-ins, the additional tasks can be performed intuitively and mostly intervention-free, thereby drastically reducing system administrators' workload and the total life cycle cost of softcopy display systems. Page 7 of 8

8 TESTS AND FREQUENCIES ON BARCO MEDICAL DISPLAYS Table 1 outlines the frequencies of softcopy QA tests on Barco s NIO and CORONIS diagnostic display systems. Frequencies are in function of available personnel and the selected display system. QA resources LOW (default) HIGH Motivation There are no people and time assigned for softcopy QA People have responsibility to do softcopy QA on a fixed timing MediCal Administrator or QAWeb is a must on these sites!!!! CORONIS with MediCal Pro Calibration timing: Only at installation, later when QA tells you to Only at installation, later when QA tells you to do so do so Intervention free QA Automatic I-Guard Check Measure Display White WEEKLY DAILY Calibration Settings Check Measure Quality Level MONTHLY WEEKLY Manual QA Visual Check (SMPTE) YEARLY MONTHLY CORONIS with QAWeb Calibration timing: Intervention free and automated Intervention free and automated Intervention free QA Asset Test Calibration Settings Test CONTINUOUS CONTINUOUS Ambient Light Test Display Test WEEKLY DAILY Compliance Test MONTHLY WEEKLY Manual QA Visual Check (SMPTE) YEARLY MONTHLY NIO with NioWatch (default) Calibration timing: Basic QA NIO with MediCal Pro Calibration timing: No recalibration required DICOM out-of-the box Not customizable Individual calibration at installation, later when QA tells you to do so Intervention free QA Measure Display White Calibration Settings Check TWICE A YEAR QUARTERLY Measure Quality Level TWICE A YEAR QUARTERLY Manual QA Visual Check (SMPTE) TWICE A YEAR MONTHLY NIO with QAWeb Individual recalibration with external sensor, once a year If requirements are high, they can buy MediCal Pro Individual calibration at installation, later when QA tells you to do so Calibration timing: Intervention free and automated Individual recalibration with external sensor, once a year Intervention free QA Asset Test Calibration Settings Test CONTINUOUS CONTINUOUS Display Test WEEKLY DAILY Manual QA Compliance Test TWICE A YEAR QUARTERLY Visual Check (SMPTE) TWICE A YEAR MONTHLY Table 1 Page 8 of 8