Practical application of AAPM Report 270 in display quality assurance: A report of Task Group 270.

Published in January 2019, AAPM Report 270 provides an update to the recommendations of the AAPM's "TG18" report. Report 270 provides new definitions of display types, updated testing patterns, and revised performance standards for the modern, flat-panel displays used as part of medical image acquisition and review. The focus of the AAPM report is on consistent image quality and appearance, and how to establish a quality assurance program to achieve those two goals. This work highlights some of the key takeaways of AAPM Report 270 and makes comparisons with existing recommendations from other references. It also provides guidance for establishing a display quality assurance program for different-sized institutions. Finally, it describes future challenges for display quality assurance and what work remains.

Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice.

OBJECTIVE: Patient shielding is standard practice in diagnostic imaging, despite growing evidence that it provides negligible or no benefit and carries a substantial risk of increasing patient dose and compromising the diagnostic efficacy of an image. The historical rationale for patient shielding is described, and the folly of its continued use is discussed. CONCLUSION: Although change is difficult, it is incumbent on radiologic technologists, medical physicists, and radiologists to abandon the practice of patient shielding in radiology.

AAPM medical physics practice guideline 10.a.: Scope of practice for clinical medical physics.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline (MPPG) represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiation requires specific training, skills, and techniques as described in each document. As the review of the previous version of AAPM Professional Policy (PP)-17 (Scope of Practice) progressed, the writing group focused on one of the main goals: to have this document accepted by regulatory and accrediting bodies. After much discussion, it was decided that this goal would be better served through a MPPG. To further advance this goal, the text was updated to reflect the rationale and processes by which the activities in the scope of practice were identified and categorized. Lastly, the AAPM Professional Council believes that this document has benefitted from public comment which is part of the MPPG process but not the AAPM Professional Policy approval process. The following terms are used in the AAPM's MPPGs: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Performance characteristics and quality assurance considerations for displays used in interventional radiology and cardiac catheterization facilities.

PURPOSE: While the performance of displays used for the acquisition and primary interpretation of medical images has been well-characterized, notably absent are publications evaluating and discussing the performance of displays used in Interventional Radiology (IR) suites and Cardiac Catheterization (CC) laboratories. The purpose of this work was to evaluate the performance of these displays and to consider the challenges in implementation of display quality assurance practices in this environment. METHODS: Ten large format displays used in IR and CC suites were evaluated. A visual inspection of available test patterns was performed followed by a quantitative evaluation of several performance characteristics including luminance ratio, luminance response function, and luminance uniformity. Additionally, the local ambient lighting conditions were evaluated. RESULTS: Luminance ratios ranged from 243.0 to 1182.1 with a mean value of 500.1 ± 289.2. The maximum deviation between the luminance response function and the DICOM Grayscale Standard Display Function ranged from 11.2% to 38.3% with a mean value of 26.2% ± 10.9%. When evaluating luminance uniformity, the mean maximum luminance deviation was 13.2% ± 3.5%. The mean value of luminance deviation from the median was 7.8% ± 1.0%. Measured values of background illuminance ranged from 29.1 to 310.0 lux with a mean value of 107.6 lux ± 80.4 lux. While no mura or bad pixels were observed during visual inspection, damage including scrapes and scratches as well as smudges was common to most of the displays. CONCLUSION: This work provides much needed data for the characterization of the performance of the large format displays used in IR and CC laboratory suites. These data may be used as a point of comparison when implementing a display QA program.

Is lead shielding of patients necessary during fluoroscopic procedures? A study based on kyphoplasty.

OBJECTIVE: To determine the benefits, risks, and limitations associated with wrapping a patient with lead shielding during fluoroscopy-guided kyphoplasty procedures as a way to reduce operator radiation exposure. MATERIALS AND METHODS: An anthropomorphic phantom was used to mimic a patient undergoing a kyphoplasty procedure under fluoroscopic guidance. Radiation measurements of the air kerma rate (AKR) were made at several locations and under various experimental conditions. First, AKR was measured at various angles along the horizontal plane of the phantom and at varying distances from the phantom, both with and without a lead apron wrapped around the lower portion of the phantom (referred to here as phantom shielding). Second, the effect of an operator's apron was simulated by suspending a lead apron between the phantom and the measurement device. AKR was measured for the four shielding conditions-phantom shielding only, operator apron only, both phantom shielding and operator apron, and no shielding. Third, AKR measurements were made at various heights and with varying C-arm angle. RESULTS: At all locations, the phantom shielding provided no substantial protection beyond that provided by an operator's own lead apron. Phantom shielding did not reduce AKR at a height comparable to that of an operator's head. CONCLUSIONS: Previous reports of using patient shielding to reduce operator exposure fail to consider the role of an operator's own lead apron in radiation protection. For an operator wearing appropriate personal lead apparel, patient shielding provides no substantial reduction in operator dose.

The effects of patient positioning when interpreting CT dose metrics: A phantom study.

PURPOSE: Review of dose metrics as part of the routine evaluation of CT protocols has become commonplace and is required by the Joint Commission and the American College of Radiology for accreditation. Most CT quality assurance programs include a review of CTDIvol and/or SSDE, both of which are affected by changes in mAs and kV. mAs, and sometimes kV, are largely determined by the Tube Current Modulation (TCM) functions of the scanner. TCM, in turn, relies on localizer scans to provide an accurate estimate of patient size. When patient size estimates are inaccurate, TCM and SSDE calculations are affected, leading to errors in both. It is important that those who are involved in reviewing CT dose indices recognize these effects to properly direct quality improvement initiatives. METHODS: An anthropomophic phantom was scanned on four clinical CT scanners using AP and PA localizers and the institution's routine abdomen protocol. Scans were repeated with the phantom at various heights relative to scanner isocenter. For each height, the projected phantom width, as shown by the localizer scans, was measured and normalized by the width of the helical scan. After each localizer scan, the TCM algorithm determined the mAs to be used for the helical scan. The scanner-reported average CTDIvol was recorded for each helical scan, and the SSDE was calculated from the projected phantom size and the scanner-reported CTDIvol at each phantom height. Last, the phantom was augmented with a lipid-gel bolus material to simulate different body mass distributions and investigate the effect of differing body habitus on projected phantom size. The results were considered in the context of optimizing dose in CT imaging, with particular attention paid to the effect on dose to breast tissue. RESULTS: Vertical mis-positioning of the phantom within the scanner led to errors in estimated phantom size of up to a factor of 1.5. These effects were more severe when localizers were acquired in the PA orientation compared with the AP orientation. Minification effects were more pronounced for AP localizers. As a consequence of inaccuracies in estimated phantom size, TCM resulted in changes in CTDIvol and SSDE of as much as a factor of 4.4 and 2.7, respectively. The effect was more pronounced when the TCM function used data from the PA, rather than the AP, localizer. CONCLUSIONS: Proper patient positioning plays a large role in the function of TCM, and hence CTDIvol and SSDE. In addition, body mass distribution may affect how patients ought to be positioned within the scanner. Understanding these effects is critical in optimizing CT scanning practices.

Imaging acquisition display performance: an evaluation and discussion of performance metrics and procedures.

When The Joint Commission updated its Requirements for Diagnostic Imaging Services for hospitals and ambulatory care facilities on July 1, 2015, among the new requirements was an annual performance evaluation for acquisition workstation displays. The purpose of this work was to evaluate a large cohort of acquisition displays used in a clinical environment and compare the results with existing performance standards provided by the American College of Radiology (ACR) and the American Association of Physicists in Medicine (AAPM). Measurements of the minimum luminance, maximum luminance, and luminance uniformity, were performed on 42 acquisition displays across multiple imaging modalities. The mean values, standard deviations, and ranges were calculated for these metrics. Additionally, visual evaluations of contrast, spatial resolution, and distortion were performed using either the Society of Motion Pictures and Television Engineers test pattern or the TG-18-QC test pattern. Finally, an evaluation of local nonuniformities was performed using either a uniform white display or the TG-18-UN80 test pattern. Displays tested were flat panel, liquid crystal displays that ranged from less than 1 to up to 10 years of use and had been built by a wide variety of manufacturers. The mean values for Lmin and Lmax for the displays tested were 0.28 ± 0.13 cd/m2 and 135.07 ± 33.35 cd/m2, respectively. The mean maximum luminance deviation for both ultrasound and non-ultrasound displays was 12.61% ± 4.85% and 14.47% ± 5.36%, respectively. Visual evaluation of display performance varied depending on several factors including brightness and contrast settings and the test pattern used for image quality assessment. This work provides a snapshot of the performance of 42 acquisition displays across several imaging modalities in clinical use at a large medical center. Comparison with existing performance standards reveals that changes in display technology and the move from cathode ray tube displays to flat panel displays may have rendered some of the tests inappropriate for modern use.

Characterization of Luminance and Color Properties of 6-MP Wide-Screen Displays.

Luminance and color performance are routinely evaluated as part of acceptance testing of displays used in diagnostic radiology. Previous work has indicated that as some diagnostic liquid crystal displays (LCDs) increase in backlight hours (BLH), the luminance measured with an external luminance meter exceeds the luminance reported by the manufacturer's built-in meter. The purposes of this work were as follows: first, to characterize several luminance and color performance characteristics for 23 Barco Coronis Fusion 6-MP MDCC 6230 color displays and, second, to provide initial data for a longitudinal study evaluating changes in luminance and color performance as BLH increase. Grayscale display conformance and maximum luminance were evaluated using a calibrated luminance meter and AAPM Task Group 18 test patterns, and agreement between target and measured luminance was calculated. Luminance uniformity was evaluated by calculating maximum luminance deviation. Color point and color uniformity were evaluated using a spectrophotometer, and the radial color distances between the corners and center of the display were calculated. Above 3 cd/m(2), there was good agreement between the target and measured luminance. At the maximum luminance, the mean difference was less than 1 %. The mean maximum luminance deviation for these displays was 10.40 ± 2.38 %. Color point was observed to be very consistent between displays with mean values of u' and v' of 0.187 ± 0.002 and 0.474 ± 0.004, respectively. Among all displays, maximum radial color distance had a mean value of 0.003 ± 0.001. These data provide a baseline for the acceptance of future displays as well as for longitudinal studies of luminance and color performance.