Standard Display Function Research Articles

A Compensation Method for Full-Field-of-View Energy Nonuniformity in Dark-and-Weak-Target Simulators.

Dark-and-weak-target simulators are used as ground-based calibration devices to test and calibrate the performance metrics of star sensors. However, these simulators are affected by full-field-of-view energy nonuniformity. This problem impacts the quality of output images and the calibration accuracy of sensors and inhibits further improvements in navigational accuracy. In the study reported in this paper, we sought to analyze the factors which affect full-field-of-view energy uniformity in dark-and-weak-target simulators. These include uneven irradiation in backlight sources, the leakage of light from LCD display panels, and the vignetting of collimating optical systems. We then established an energy transfer model of a dark-and-weak-target simulator based on the propagation of a point light source and proposed a self-adaptive compensation algorithm based on pixel-by-pixel fitting. This algorithm used a sensor to capture the output image of a dark-and-weak-target simulator and iteratively calculated the response error matrix of the simulator. Finally, we validated the feasibility and effectiveness of the compensation algorithm by acquiring images using a self-built test system. The results showed that, after compensating an output image of the dark-and-weak-target simulator, the grayscale standard display function (SDF) of the acquired sensor image was reduced by about 50% overall, so the acquisition image was more accurately compensated, and the desired level of grayscale distribution was obtained. This study provides a reference for improving the quality of output images from dark-and-weak-target simulators, so that the working environments of star sensors may be more realistically simulated, and their detection performance improved.

Display Performance of X-ray Image Output from DICOM-embedded Printer to Paper-based Hard Copy Print: Comparison with X-ray Image on LCD

We have been using a paper-based hard copy print (paper print) system of X-ray images, in which digital imaging and communications in medicine (DICOM) data can be directly output on papers from medical imaging systems or from a picture archiving and communication system (PACS) server, and they are utilized as patient referral materials or for preoperative planning. The purpose of this study was to compare the display performance of X-ray images on the printed paper and that on the liquid crystal display (LCD). We measured contrast response to verify consistency of image appearance on both display systems. The contrast resolution was assessed by a CDRAD phantom. The spatial resolution was assessed by an X-ray test chart. The contrast response of the paper printer was not concordant with the grayscale standard display function (GSDF). The difference between the measured contrast response and the ideal GSDF on the paper was large in the high-density area. The low-contrast resolution on the paper was inferior to that on the LCD. The spatial resolving power on the paper was superior to that on the LCD. The display performance of the paper printer for X-ray images was clarified. X-ray images printed on the paper should be used carefully taking account of their characteristics of display performance.

Studies on the Effectiveness of High-luminance Monitors in Mammography Softcopy Interpretation

Recently, monitors with maximum luminance exceeding 2000 cd/m2 (high-luminance monitor) have been used for diagnostic mammography. In this study, we examined the visibility of high-luminance monitors by converting luminance meter measurements into the just noticeable difference (JND) Index. The ambient light was also examined at the same time. The high-luminance monitor is a 21.3-inch IPS monochrome monitor with a maximum luminance of 3000 cd/m2. Experiments were conducted with a minimum luminance of 0.6 cd/m2 and a maximum luminance of 500, 850, and 1200 cd/m2. The luminance ratio was set to 1 : 2000 and the maximum luminance was changed to 500, 1000, and 2000 cd/m2. The ambient light was varied to 8.7, 36.1, 61.3, and 129.6 lx. The Japan Radiological Society recommended luminance values for each stage of phantom and Grayscale Standard Display Function curves were measured. The JND increased as the maximum luminance was increased for both the case with the same minimum luminance and the case with the same luminance ratio, and visibility was improved. In both the case of the same minimum luminance and the case of the same luminance ratio, the JND was found to increase as the maximum luminance was increased. The results suggest that high-luminance monitors may improve visibility and allow for higher ambient light settings. Furthermore, the degree of eye fatigue needs to be verified.

Diagnostic Accuracy of Caries and Periapical Lesions on a Monitor with and without DICOM-GSDF Calibration Under Different Ambient Light Conditions.

To evaluate the diagnostic accuracy of caries and periapical lesions on a monitor with and without DICOM part 14: grayscale standard display function (DICOM-GSDF) calibration under different ambient light conditions. Forty digital bitewing radiographs were selected, with or without radiographic images of carious lesions and forty digital periapical radiographs with or without periapical lesions were selected from archives of the Radiology Department at the University Hospital of the Federal University of Sergipe. The gold standard radiographic images were determined through consensus between two radiologists with more than 15 and 30 years of experience. The selected radiographs were evaluated on a LG LED monitor with and without DICOM-GSDF calibration under different ambient light conditions: Lx1 (low ambient lighting), Lx2 (moderate ambient lighting) and Lx3 (high ambient lighting). Kappa (Kw) values determined that evaluator 1 showed almost perfect agreement for all devices, while evaluator 2 presented a substantial agreement for all devices. Monitors with and without DICOM-GSDF calibration have similar accuracy values. The three ambient light conditions analyzed have similar accuracy and can be used for caries lesions diagnosis (p > 0.05); however, the best diagnostic accuracy of periapical lesions was found in Lx 2. The displays with and without DICOM-GSDF calibration studied in this research have similar accuracy and can be used to evaluate digital radiographs without changing the diagnostic capacity. The different ambient lighting conditions did not influence the evaluation of caries lesions. The best diagnostic accuracy of periapical lesions was found in moderate ambient lighting.

IMPROVING IMAGE QUALITY BY INCREASING THE AMOUNT OF LIGHT IN THE READING ROOM.

Many standards and guidelines related to the use of medical displays require viewers to be in dark rooms. The purpose of this theoretical study was to examine the validity of some commonly used requirements in terms of image contrast and contrast stability in rooms with fluctuating illuminance. By using the grayscale standard display function (Dicom part 14), contrast was calculated for several combinations of display minimum and maximum luminance as well as the possible range of illuminance fluctuations that will not exceed given contrast tolerance levels. The results show that some requirements are only valid in dark viewing rooms, which are also usually recommended or enforced. However, image contrast, contrast stability, ergonomics and fatigue would improve by using brighter displays in brighter rooms. With a better set of requirements, it would also be possible for displays in brighter rooms, like dentist departments and operating rooms, to conform to the requirements.

Impact of calibration methods for color medical displays on interpreting brain SPECT images.

Color images are visualized on medical monitors that are adjusted by a grayscale standard display function (GSDF) or γ2.2. Although the GSDF is visually displayed as a linear graded grayscale, it does not specify how color medical images should be presented. On the other hand, the usual gamma setting for color images is γ2.2, but it has not been standardized. The color standard display function (CSDF) has recently been proposed as a standardized gamma setting for color medical monitors. However, the influence of various gamma settings on image characteristics should be determined. The present study aimed to identify differences in color-scale characteristics on nuclear medicine images displayed on medical monitors adjusted by CSDF, GSDF, and γ2.2. Transverse normal (n=1) and abnormal (n=5) brain perfusion images were generated using a mathematical digital phantom. Transverse phantom and clinical brain images are shown using the clinically applied eight-color scale. Five nuclear medicine experts visually assessed phantom and clinical images using a defect severity scale that ranged from zero (no defect) to four (defect). Receiver operating characteristic curves were created and areas under the curves (AUCs) were analyzed. Defect scores for the clinical study were evaluated in the nine segments on basal ganglia slice, and defect scores were summed for each patient. The average defect score for color A significantly differed in multiple comparison tests, but not in post hoc tests. The ranges of AUC for CSDF, GSDF, and γ2.2 were 0.86-0.94, 0.82-0.94, and 0.88-0.97, respectively. The AUCs of CSDF in all color scales did not significantly differ from other gamma settings. The summed defect scores of CSDF were similar to those of other gamma settings. Nuclear medicine images were equally valid when adjusted by CSDF even at various gamma settings. Nuclear medicine images can be evaluated equally using any gamma setting. Nonetheless, the color gamma setting for medical monitors should be standardized.

A Neural Network Processing Method Based on Self-Assembly Equipment for Optical Image Display Standardization

Optical image is a kind of important data for communication because it is a two or three -dimensions data set to express communication information such as geographical signal, medical signal, remote sensing signal, etc. Thus, how to express the optical image properly is critical for the communication analytics. A new display method for optical image is described which is derived from the concept-Grayscale Standard Display Function (GSDF) which has been defined in DICOM, a medical image standard. The method analysis GSDF based on neural network processing which is different to DICOM. And the training data are from a self-assembly Equipment in NIM which is a traceable optical display equipment. Thus, the method has common usage for all optical image display, exceeding medical image. Furthermore, it is suitable for standardization because of the traceability.

Quality Control of Display Devices for Medical Radiodiagnosis Employing the Standard TG18, GSDF and JND

Introduction: This work presents a study on the procedures for evaluating the quality of imaging display devices in radiology, considering the characteristic luminance curve obtained experimentally versus the Just Noticeable Difference (JND) and the lifetime of digital display devices. Materials & Methods: The evaluations were done using image patterns published by the American Association of Physicists in Medicine on Digital Imaging and Communication in Medicine (DICOM) and the Grayscale Standard Display Function (GSDF), viewed in DICOM software, with various shades of gray. A digital luximeter was used as the luminance meter. A correlation with the time of use of the devices was performed to classify the digital devices as primary (suitable for medical diagnosis) or secondary (suitable only for visualization of medical images). Results & Discussion: Among the monitors evaluated, those with a resolution between 2 and 5 megapixels were classified as primary for up to 50, 000 hours of use, and some above that time limit present behavior equivalent to secondary monitors. Monitoring the temporal evolution of the use of devices is important to avoid errors in medical diagnosis. Conclusion: The use of a calibrated digital luximeter with an illuminance unit conversion factor in luminance defined by this equipment was shown to be an alternative to replace a photometer when this latter is not available.

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

PurposeWhile 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.MethodsTen 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.ResultsLuminance 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.ConclusionThis 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.

DICOM Calibration of Commercial Off-The-Shelf (COTS) display devices for use in radiotherapy

In a modern, distributed radiotherapy environment image evaluation is becoming increasingly common at office desktop computers, many of which will be equipped with inexpensive Commercial Off-The-Shelf (COTS) display devices. To ensure consistency of image interpretation it is important to achieve consistency of display device performance. 15 displays (4 different models from 2 manufacturers) were characterised and the potential for their calibration against the DICOM Greyscale Standard Display Function (GSDF) explored. Each display’s luminance output was measured as a function of grey-level using a calibrated LXChroma photometer (IBA Dosimetry, Germany) with an automated sequence of greyscale images. A modification to the graphics card look-up table was calculated to adjust system performance to match the GSDF and the measurements were repeated. Prior to calibration there was considerable variation in performance across displays, including between those of the same model and manufacturer. The max luminance and max/min luminance ratio ranged from 94–401 cd/m2 (m = 213 cd/m2, sd = 95 cd/m2) and 85–1005 (m = 228, sd = 223) respectively. Initially, no display matched the GSDF to within the ‘secondary class’ limit of ±20% across all light levels, with the error being between 0.2 and 63.0%. Following calibration, all displays but one were within ±15% of the GSDF, with the outlier being +21% at a single measurement point. Care must be taken when deploying COTS displays because of initial variability in performance. However, performance can be successfully standardised through calibration against the GSDF. When appropriately calibrated, high quality yet relatively inexpensive COTS displays may offer a suitable alternative to traditional, expensive ‘medical grade’ display devices.

The assessment and characterization of the built-in internal photometer of primary diagnostic monitors.

The purpose of this work was to perform the initial evaluation of primary diagnostic monitor (PDM) characteristics following the implementation of New York City quality assurance (NYC QA) regulations on January 1, 2016, and compare the results of the QA measurements performed by an external photometer and the PDM manufacturer's built‐in photometer. TG‐18 and Society of Motion Picture and Television Engineers test patterns were used to evaluate monitor performance. Overall, 79 PDMs were included in the analysis. The verification of grayscale standard display function (GSDF) calibration, using a built‐in photometer, showed that only 2 out of 79 PDMs failed calibration. However, the same measurements performed by the external luminance meter showed that 15 out of 79 monitors had failed GSDF calibration. Measurements of the PDMs maximum luminance (Lmax), using an external photometer showed that 10 out of 53 PDMs calibrated for Lmax = 400 cd/m2 and 17 out of 26 PDMs calibrated for Lmax = 500 cd/m2 do not meet the manufacturer's recommended 10% tolerance limit for the target Lmax calibration. Two PDMs did not pass the Lmax ≥ 350 cd/m2 NYC QA regulations with Lmax = 331 cd/m2 and Lmax = 340 cd/m2. All tested PDMs exceeded the minimum luminance ratio (LR) of 250:1 as required by NYC QA regulations. Measurements taken of Lmax and LR performed by a built‐in photometer showed that none of the PDMs had failed the NYC QA regulations. All PDMs passed the luminance uniformity test with a maximum nonuniformity of 17% (according to NYC regulations it must be less than 30%). The luminance uniformity test could only be performed using an external photometer. The evaluation of 79 PDMs of various ages and models demonstrated up to 18% disagreement between luminance measurements performed by the manufacturer's built‐in photometer when compared with those performed by an externally calibrated luminance meter. These disagreements were larger for older PDMs.

The importance of color quality assurance of medical displays

Introduction Medical images are increasingly analyzed based on color by departments such as Nuclear Medicine, Dermatology, Plastic Surgery, Pathology and Gastroenterology to mark a tumor, to observe hematoma and to discriminate between benign and malignant tissues. Purpose The purpose of this research is to create awareness concerning the importance of color quality assurance and to develop and test a method to review color displays analog to the Grayscale Standard Display Function. Materials and methods In our hospital several displays (diagnostic, medical review, professional and consumer display) were measured with a luminance-colorimeter (Iba: LXchroma). Since standardized color test patterns don’t exist, test patterns were developed according to the DICOM standard analog to the TG-18LN steps for each primary (RGB) and secondary color (CMY). The chromaticity coordinate and luminance of each color-contraststep was measured. The metric distance within the perceptive color space CIE1976 (CIEDE2000) between the steps for each color was calculated. A distance of ⩾2.3 corresponds to a just noticeable difference (JND), which was empirically determined using MacAddams-ellipses. Results Results show that the measured displays poorly visualize the provided contrast steps. Furthermore, the available color space of the display could be restricted due to the small luminance range. Conclusion Medical displays should be included in a color quality assurance program to prevent possible misdiagnosis, although there are no practical guidelines or standard criteria available yet. The color contrast behavior of a medical display could be reviewed using the CIEDE2000 metric, but display manufactures should focus on calibration possibilities to optimize the CIEDE2000 metric to the empirical JNDs. Disclosure Nothing to disclose.

Method for Adapting the Grayscale Standard Display Function to the Aging Eye.

Perceptual linearity of grayscale images based on a contrast sensitivity model is a widely recognized and used standard for medical imaging visualization. This approach ensures consistency across devices and provides perception of luminance variations in direct relationship to changes in image values. We analyze the effect of aging of the human eye on the precept of linearity and demonstrate that not only the number of just-noticeable differences diminishes for older subjects but also linearity across the range of luminance values is significantly affected. While loss of JNDs is inevitable for a fixed luminance range, our findings suggest possible corrective approaches for maintaining linearity.

Color standard display function: A proposed extension of DICOM GSDF.

Color images are being used more in medical imaging for a broad range of modalities and applications. While in the past, color was mostly used for annotations, today color is also widely being used for diagnostic purposes. Surprisingly enough, there is no agreed upon standard yet that describes how color medical images need to be visualized and how calibration and quality assurance of color medical displays need to be performed. This paper proposes color standard display function (CSDF) which is an extension of the DICOM GSDF standard toward color. CSDF defines how color medical displays need to be calibrated and how QA can be performed to obtain perceptually linear behavior not only for grayscale but also for color. The proposed CSDF algorithm uses DICOM GSDF calibration as a starting point and subsequently uses a color visual difference metric to redistribute colors in order to obtain perceptual linearity not only for the grayscale behavior but also for the color behavior. A clear calibration and quality assurance algorithm is defined and is validated on a wide range of different display systems. A detailed description of the proposed CSDF calibration and quality assurance algorithms is provided. These algorithms have been tested extensively on three types of display systems: consumer displays, professional displays, and medical grade displays. Test results are reported both for the calibration algorithm as well as for the quantitative and visual quality assurance methods. The tests confirm that the described algorithm generates consistent results and is able to increase perceptual linearity for color and grayscale visualization. Moreover the proposed algorithms are working well on a wide range of display systems. CSDF has been proposed as an extension of the DICOM GSDF standard toward color. Calibration and QA algorithms for CSDF have been described in detail. The proposed algorithms have been tested on several types of display systems and the results confirm that CSDF largely increases the perceptual linearity of visualized colors, while at the same time remaining compliant with DICOM GSDF.

The effect of time in use on the display performance of the iPad

The aim of this study was to evaluate changes to the luminance, luminance uniformity and conformance to the digital imaging and communication in medicine greyscale standard display function (GSDF) as a function of time in use for the iPad. Luminance measurements of the American Association of Physicists in Medicine (AAPM) Group 18 task group (TG18) luminance uniformity and luminance test patterns (TG18-UNL and TG18-LN8) were performed using a calibrated near-range luminance meter. Nine sets of measurements were taken, where the time in use of the iPad ranged from 0 to 2500 h. The maximum luminance (Lmax) of the display decreased (367-338 cdm(-2)) as a function of time. The minimum luminance remained constant. The maximum non-uniformity coefficient was 11%. Luminance uniformity decreased slightly as a function of time in use. The conformance of the iPad deviated from the GSDF curve at commencement of use. Deviation did not increase as a function of time in use. This study has demonstrated that the iPad display exhibits luminance degradation typical of liquid crystal displays. The Lmax of the iPad fell below the American College of Radiology-AAPM-Society of Imaging Informatics in Medicine recommendations for primary displays (>350 cdm(-2)) at approximately 1000 h in use. The Lmax recommendation for secondary displays (>250 cdm(-2)) was exceeded during the entire study. The maximum non-uniformity coefficient did not exceed the recommendations for either primary or secondary displays. The deviation from the GSDF exceeded the recommendations of the TG18 for use as either a primary or secondary display. The brightness, uniformity and contrast response are reasonably stable over the useful lifetime of the device; however, the device fails to meet the contrast response standard for either a primary or secondary display.

Effect of display type and room illuminance in chest radiographs.

To compare diagnostic accuracy in the detection of subtle chest lesions on digital chest radiographs using medical-grade displays, consumer-grade displays, and tablet devices under bright and dim ambient light. Five experienced radiologists independently assessed 50 chest radiographs (32 with subtle pulmonary findings and 18 without apparent findings) under bright (510lx) and dim (16lx) ambient lighting. Computed tomography was used as the reference standard for interstitial and nodular lesions and follow-up chest radiograph for pneumothorax. Diagnostic accuracy and sensitivity were calculated for assessments carried out in all displays and compared using the McNemar test. The level of significance was set to p < 0.05. Significant differences in sensitivity between the assessments under bright and dim lighting were found among consumer-grade displays in interstitial opacities with, and in pneumothorax without, Digital Imaging and Communication in Medicine-Grayscale Standard Display Function (DICOM-GSDF) calibration. Compared to 6 megapixel (MP) display under bright lighting, sensitivity in pneumothorax was lower in the tablet device and the consumer-grade display. Sensitivity in interstitial opacities was lower in the DICOM-GSDF calibrated consumer-grade display. A consumer-grade display with or without DICOM-GSDF calibration or a tablet device is not suitable for reading digital chest radiographs in bright lighting. No significant differences were observed between five displays in dim light. • Ambient lighting affects performance of consumer-grade displays (with or without DICOM-GSDF calibration). • Bright light decreases detection of pneumothorax on non-medical displays. • Bright light decreases detection of interstitial opacities on DICOM-GSDF-calibrated, consumer-grade displays. • Dim light is sufficient to detect subtle chest lesions from all displays.

WE-D-204-04: Color Standard Display Function (CSDF): A Proposed Extension of DICOM GSDF

Purpose: Use of color images in medical imaging has increased significantly. As of today there is no agreed upon standard on how color information needs to be visualized on medical color displays, resulting into large variability of color appearance and it making consistency and quality assurance a challenge. This paper presents a proposed extension of DICOM GSDF towards color. Methods: An extension of the GSDF (Greyscale Standard Display Function) to color is proposed: “CSDF” (color standard display function). CSDF is based on deltaE2000 and offers a perceptually linear color behavior. CSDF uses GSDF as its neutral grey behavior and as such allows for simultaneous presentation of color and greyscale medical images. Results: Compared to the presentation given at the 2015 AAPM annual meeting, the algorithm has been improved, QA metrics have been added, and more elaborate validation has been done.Extensive tests were performed on a variety of displays with different characteristics. For each display, color behavior was characterized, the calibration was executed and a QA/compliance test was performed before and after calibration to quantify the effect of the calibration. Results confirm that CSDF significantly improves perceptual color linearity and that the algorithm is stable and reproducible. Furthermore, CSDF calibration was applied to a variety of medical color images. Results indicate that because of the improved perceptual linearity, CSDF can increase perceived contrast of clinically relevant features in a variety of color medical images. Conclusion: There is a need for an extension of GSDF towards color visualization in order to guarantee consistency and quality. During the 2014 AAPM annual meeting a first proposal for a CSDF (color standard display function) was made. Now an improved and much more validated version of the proposed CSDF will be presented, as well as QA metrics that can be used for measuring calibration quality. Tom Kimpe, Johan Rostang, Gert Van Hoey and Albert Xthona are employees of Barco Healthcare

WE-D-204-03: A Six-Year Longitudinal Evaluation of the DICOM GSDF Conformance Stability of LCD Monitors

Purpose: The calibration of monitors in radiology is critical to ensure a standardized reading environment. If left unchecked, monitors initially calibrated to follow the DICOM Grayscale Standard Display Function (GSDF) can fall out of calibration. This work presents a quantitative evaluation of the stability of a cohort of monitors with similar deployment times and clinical utilization. Methods: Fifty-four liquid crystal display (LCD) monitors (NEC L200ME) were deployed for clinical use in 2009. At that time, a subset of eight of these monitors were used to generate a look-up table (LUT) using the open-source software pacsDisplay. The software was used to load the LUT to the graphics card of the computer in order to make the monitors compliant with the GSDF. The luminance response of the monitors was evaluated twice over six years, once in 2011 and again in 2015. Results: As expected, the maximum luminance of the monitors decreased over time, with an average reduction from 2009 of 35% in 2011, and 53% in 2015. The luminance ratio (maximum luminance divided by the minimum) also decreased, with the all of the decrease occurring in the first two years (average 20%). There was an overall increase in relative error compared with the DICOM GSDF from measurement to measurement, indicating that deviation from the GSDF increases with monitor luminance reduction. Along with changes in luminance, several other issues were identified during the testing, including non-uniformities, bad pixels, and missing calibration software. Conclusion: From the initial installation of these monitors, most of the degradation occurred during the first two years, highlighting the importance of routine clinical testing of displays. Following such quality assurance, displays could be either re-calibrated or replaced depending on different thresholds. In addition, other issues not related to luminance could be identified and corrected.

SU‐E‐P‐29: Testing Display Monitors for GSDF Compliance ‐ a Practical Approach

Purpose:To develop a simple technique for testing display monitors for compliance with the DICOM Grayscale Standard Display Function (GSDF), in accordance with the recommendations of AAPM Task Group 18.Methods:We have developed a spreadsheet that can be used to compare both the luminance response and contrast response of a display to the GSDF, using luminance measurements of the SMPTE test pattern. The contrast response compares the slope of the GSDF j‐index as a function of pixel value to that of the GSDF function, and should lie within the range 0.85 to 1.15.Results:We present the results of measurements both of primary diagnostic displays and of ultrasound and acquisition workstations, all at a tertiary care hospital. The Barco displays in the radiographic reading rooms are GSDF compliant or nearly so, while those in the ultrasound reading rooms and at the acquisition workstations generally show significantly higher contrast at low luminance levels than they would if GSDF compliant, and lower contrast at high luminance levels.Conclusion:The spreadsheet that we developed allows a simple comparison of measured display contrast response to the GSDF. Although we used the SMPTE pattern, the same technique could be used with other grayscale patterns, such as TG18‐QC and TG18‐PQC.

WE‐D‐9A‐03: CSDF: A Color Extension of the Grayscale Standard Display Function

Purpose:Use of color images in medical imaging has increased significantly the last few years. As of today there is no agreed standard on how color information needs to be visualized on medical color displays, resulting into large variability of color appearance and it making consistency and quality assurance a challenge. This paper presents a proposal for an extension of DICOM GSDF towards color.Methods:Visualization needs for several color modalities (multimodality imaging, nuclear medicine, digital pathology, quantitative imaging applications…) have been studied. On this basis a proposal was made for desired color behavior of color medical display systems and its behavior and effect on color medical images was analyzed.Results:Several medical color modalities could benefit from perceptually linear color visualization for similar reasons as why GSDF was put in place for greyscale medical images. An extension of the GSDF (Greyscale Standard Display Function) to color is proposed: CSDF (color standard display function). CSDF is based on deltaE2000 and offers a perceptually linear color behavior. CSDF uses GSDF as its neutral grey behavior. A comparison between sRGB/GSDF and CSDF confirms that CSDF significantly improves perceptual color linearity. Furthermore, results also indicate that because of the improved perceptual linearity, CSDF has the potential to increase perceived contrast of clinically relevant color features.Conclusion:There is a need for an extension of GSDF towards color visualization in order to guarantee consistency and quality. A first proposal (CSDF) for such extension has been made. Behavior of a CSDF calibrated display has been characterized and compared with sRGB/GSDF behavior. First results indicate that CSDF could have a positive influence on perceived contrast of clinically relevant color features and could offer benefits for quantitative imaging applications.Authors are employees of Barco Healthcare