Introduction to grayscale calibration and related aspects of medical imaging grade liquid crystal displays

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

PURPOSE

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).

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Tablets as an Option for Telemedicine-Evaluation of Diagnostic Performance and Efficiency in Intracranial Arterial Aneurysm Detection

Purpose: To evaluate a commercially available mobile device for the highly specialized task of detection of intracranial arterial aneurysm in telemedicine. Methods: Six radiologists with three different levels of experience retrospectively interpreted 60 computed tomography (CT) angiographies for the presence of intracranial arterial aneurysm, among them 30 cases with confirmed positive findings. Each radiologist reviewed the angiography datasets twice: once on a dedicated medical-grade workstation and on a commercially available mobile consumer-grade tablet with an interval of 3 months. Diagnostic performance, reading efficiency and subjective scorings including diagnostic confidence were analyzed and compared. Results: Diagnostic performance was comparable on both devices regardless of readers’ experience, and no significant differences in sensitivity (66–87.5%) and specificity (79.4–87%) were found. Results obtained with tablets and medical workstations were also comparable in terms of subjective assessment across all reader groups. Conclusions: There was no significant difference between tablet and workstation readings of angiography datasets for the presence of intracranial arterial aneurysm. Sensitivity, specificity, efficiency and subjective scorings were similar with the two devices for all three reader groups. While medical workstations are 10 times more expensive, tablets allow higher mobility especially for radiologists on call.

Evaluation of diagnostic accuracy of intracranial aneurysm detection using medical-grade versus commercial consumer-grade displays and different image reconstructions against the background of process optimization for telemedicine

BACKGROUND

Process optimization in computed tomography (CT) and telemedicine.

PURPOSE

To compare image quality and objective diagnostic accuracy of medical-grade and consumer-grade digital displays/computer terminals for detection of intracranial aneurysms.

MATERIAL AND METHODS

Four radiologists with different levels of experience retrospectively read a total of 60 patients including 30 cases of proven therapy-naïve intracranial aneurysm detectable on a medical-grade grayscale calibrated display. They had 5 min per case reading the first 20 datasets using only axial slices, the next 20 patients using axial slices and multiplanar reconstructions (MPRs), and the last 20 patients using axial slices, MPRs, and maximum intensity projections (MIPs). Three months after the first reading session on a medical-grade display, they read all datasets again under the same standardized conditions but on a consumer-grade display. Diagnostic performance, subjective diagnostic confidence, and reading speed were analyzed and compared. Readers rated image quality on a five-point Likert scale.

RESULTS

Diagnostic accuracy did not differ significantly with areas under the curve of 0.717-0.809 for all readers on both display devices. Sensitivity and specificity did not increase significantly when adding MPRs and/or MIPs. Reading speed was similar with both devices. There were no significant differences in subjective image quality scores, and overall inter-reader variability of all subjective parameters correlated positively between the two devices (P <0.001-0.011).

CONCLUSION

Diagnostic accuracy and readers' diagnostic confidence in detecting and ruling out intracranial aneurysm were similar on commercial-grade and medical-grade displays. Additional reconstructions did not increase sensitivity/specificity or reduce the time needed for diagnosis.

Accuracy and Reliability of the Recommendation for IV Thrombolysis in Acute Ischemic Stroke Based on Interpretation of Head CT on a Smartphone or a Laptop

OBJECTIVE. The objective of this study was to assess the accuracy and reliability of IV thrombolysis recommendations made after interpretation of head CT images of patients with symptoms of acute stroke displayed on smartphone or laptop reading systems compared with those made after interpretation of images displayed on a medical workstation monitor. MATERIALS AND METHODS. This retrospective study was institutional review board-approved, and the requirement for informed consent was waived. We used a factorial design including 2256 interpretations (188 patients, four neuroradiologists, and three reading systems). To evaluate the reliability, we calculated the intraobserver and interobserver agreements using the intraclass correlation coefficient (ICC) and the following interpretation variables: hemorrhagic lesions, intraaxial neoplasm, stroke dating (acute, subacute, and chronic), hyperdense arteries, and infarct size assessment. Accuracy equivalence tests were performed for the IV thrombolysis recommendation; for this variable, sensitivity, specificity, and ROC curves were evaluated. RESULTS. Good or very good interobserver and intraobserver agreements were obtained after interpretation of each variable. The IV thrombolysis recommendation showed very good interobserver agreements (ICC ≥ 0.85) and very good intraobserver agreements (ICC ≥ 0.81). For the IV thrombolysis recommendation, the AUC values (0.83-0.84) and sensitivities (0.94-0.95) were equivalent among all the reading systems at a 5% equivalent threshold. CONCLUSION. Our study found that mobile devices are reliable and accurate to help stroke teams to decide whether to administer IV thrombolysis in patients with acute stroke.

Comparing medical grade to commercial grade display in a radiation oncology environment

Electronic displays are used in every modern day medical clinic. They are used to view images that are needed to diagnose, treat, and follow-up on patients with a variety of conditions. The type of electronic display used varies from department to department. Currently, a type of displays called medical grade displays are used to evaluate and diagnose disease and conditions. Alternatively, commercial or entry level professional displays are used for almost everything else. In the field of radiation oncology medical images are often used to plan the treatment course for each patient. These images are always viewed using a commercial grade display. An experiment was completed to examine the role a medical grade display might have in a radiation oncology setting. Our study had certified dosimetrists and radiation oncologists view medical images on both a medical grade and commercial grade display and rank their preference on a scale. The observers assessed the images in different categories (Contrast, resolution, and sharpness) and also commented on their preference. Results indicated that the medical grade display performed better than the commercial grade display in every image quality category.

Will Digital Pathology be as Disruptive as Genomics?

Digital pathology is the science of performing traditional pathological assessment in a digital environment. A digital transition is long overdue since histochemical analysis such as hematoxylin and eosin staining has remained unchanged in over 100 years. Importantly, the digitization of whole slide images further lends itself to advances in computational pathology and artificial intelligence to transform qualitative assessment into quantitative assessment. The impact of this transition from a computational infrastructure perspective is reminiscent of a similar transition in the field of genomics. In this article, I describe some of the similarities between genomics and digital pathology as well as highlight some key lessons learned to prevent the same mistakes and delays that slowed the genomics revolution.

Comparison of a Medical-Grade Monitor vs Commercial Off-the-Shelf Display for Mitotic Figure Enumeration and Small Object (Helicobacter pylori) Detection

OBJECTIVES

To examine the performance of a commercial off-the-shelf (COTS) monitor vs a medical-grade (MG) monitor for small object enumeration in standardized digital pathology images.

METHODS

Pathologists reviewed 35 melanoma or 35 gastric biopsy images using the MG and COTS displays, with a 2-week washout period. Mitotic figure or Helicobacter pylori burden enumerations were compared with reference values reported by an expert subspecialist pathologist using a light microscope. Subjective evaluations of image color, brightness, and overall quality were also obtained.

RESULTS

There was substantial agreement between the mitotic counts obtained by the evaluating pathologists between monitors and the reference mitotic figure or H pylori burden assessments. Six of the nine evaluating pathologists subjectively evaluated the monitors as substantially similar.

CONCLUSIONS

These findings are consistent with previous studies demonstrating that color calibration has limited impact on diagnostic accuracy and suggest that noncalibrated displays could be considered for fine assessment tasks.

Comparison of medical-grade and calibrated consumer-grade displays for diagnosis of subtle bone fissures

OBJECTIVE

To compare the diagnostic accuracy of medical-grade and calibrated consumer-grade digital displays for the detection of subtle bone fissures.

METHODS

Three experienced radiologists assessed 96 digital radiographs, 40 without and 56 with subtle bone fissures, for the presence or absence of fissures in various bones using one consumer-grade and two medical-grade displays calibrated according to the DICOM-Grayscale Standard Display Function. The reference standard was consensus reading. Subjective image quality was also assessed by the three readers. Statistical analysis was performed using receiver operating characteristic analysis and by calculating the sensitivity, specificity, and Youden's J for each combination of reader and display. Cohen's unweighted kappa was calculated to assess inter-rater agreement. Subjective image quality was compared using the Wilcoxon signed-rank test.

RESULTS

No significant differences were found for the assessment of subjective image quality. Diagnostic performance was similar across all readers and displays, with Youden's J ranging from 0.443 to 0.661. The differences were influenced more by the reader than by the display used for the assessment.

CONCLUSION

No significant differences were found between medical-grade and calibrated consumer-grade displays with regard to their diagnostic performance in assessing subtle bone fissures. Calibrated consumer-grade displays may be sufficient for most radiological examinations.

KEY POINTS

• Diagnostic performance of calibrated consumer-grade displays is comparable to medical-grade displays. • There is no significant difference with regard to subjective image quality. • Use of calibrated consumer-grade displays could cut display costs by 60-80%.

Numerical Evaluation of Image Contrast for Thicker and Thinner Objects among Current Intraoral Digital Imaging Systems

The purpose is to evaluate the performance of current intraoral digital detectors in detail using a precise phantom and new method. Two aluminum step wedges in 0.5 mm steps were exposed by two photostimulable phosphor plate (PSP) systems—one with automatic exposure compensation (AEC) and the other without AEC—and a CCD sensor. Images were obtained with 3 doses at 60 kV. The effect of metallic material also was evaluated. The contrast-to-noise ratio (CNR) for thinner steps and the low contrast value (LCV) for thicker steps were obtained. The CCD system was the best under all conditions (P < 0.001), although the Gray value was sensitive to the dose, and the Gray value-dose relation varied greatly. The PSP system with AEC was superior to that without AEC for the LCV (P < 0.001) but was inferior to it regarding the CNR (P < 0.001). CNR and LCV in the PSP system without AEC were not affected by the metallic plate. Intraoral digital imaging systems should be chosen according to their diagnostic purpose. PSP system with AEC may be the best for detecting molar proximal caries, whereas the PSP system without AEC may be better for evaluating small bone regeneration in periodontal disease. The CCD system provided the best performance.

Color standard display function: A proposed extension of DICOM GSDF

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

An Evaluation of Performance Characteristics of Primary Display Devices

The aim of this study was to complete a full evaluation of the new EIZO RX850 liquid crystal display and compare it to two currently used medical displays in Australia (EIZO GS510 and Barco MDCG 5121). The American Association of Physicists in Medicine (AAPM) Task Group 18 Quality Control test pattern was used to assess the performance of three high-resolution primary medical displays: EIZO RX850, EIZO GS510, and Barco MDCG 5121. A Konica Minolta spectroradiometer (CS-2000) was used to assess luminance response, non-uniformity, veiling glare, and color uniformity. Qualitative evaluation of noise was also performed. Seven breast lesions were displayed on each monitor and photographed with a calibrated 5.5-MP Olympus E-1 digital SLR camera. ImageJ software was used to sample pixel information from each lesion and surrounding background to calculate their conspicuity index on each of the displays. All monitor fulfilled all AAPM acceptance criteria. The performance characteristics for EIZO RX850, Barco MDCG 5121, and EIZO GS510 respectively were as follows: maximum luminance (490, 500.5, and 413 cd/m(2)), minimum luminance (0.724, 1.170, and 0.92 cd/m(2)), contrast ratio (675:1, 428:1, 449:1), just-noticeable difference index (635, 622, 609), non-uniformity (20, 5.92, and 8.5 %), veiling glare (GR = 2465.6, 720.4, 1249.8), and color uniformity (Δu'v' = +0.003, +0.002, +0.002). All monitors demonstrated low noise levels. The conspicuity index (χ) of the lesions was slightly higher in the EIZO RX850 display. All medical displays fulfilled AAPM performance criteria, and performance characteristics of EIZO RX850 are equal to or better than those of the Barco MDCG 5121 and EIZO GS510 displays.

Radiological interpretation of images displayed on tablet computers: a systematic review

OBJECTIVE

To review the published evidence and to determine if radiological diagnostic accuracy is compromised when images are displayed on a tablet computer and thereby inform practice on using tablet computers for radiological interpretation by on-call radiologists.

METHODS

We searched the PubMed and EMBASE databases for studies on the diagnostic accuracy or diagnostic reliability of images interpreted on tablet computers. Studies were screened for inclusion based on pre-determined inclusion and exclusion criteria. Studies were assessed for quality and risk of bias using Quality Appraisal of Diagnostic Reliability Studies or the revised Quality Assessment of Diagnostic Accuracy Studies tool. Treatment of studies was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

RESULTS

11 studies met the inclusion criteria. 10 of these studies tested the Apple iPad(®) (Apple, Cupertino, CA). The included studies reported high sensitivity (84-98%), specificity (74-100%) and accuracy rates (98-100%) for radiological diagnosis. There was no statistically significant difference in accuracy between a tablet computer and a digital imaging and communication in medicine-calibrated control display. There was a near complete consensus from authors on the non-inferiority of diagnostic accuracy of images displayed on a tablet computer. All of the included studies were judged to be at risk of bias.

CONCLUSION

Our findings suggest that the diagnostic accuracy of radiological interpretation is not compromised by using a tablet computer. This result is only relevant to the Apple iPad and to the modalities of CT, MRI and plain radiography.

ADVANCES IN KNOWLEDGE

The iPad may be appropriate for an on-call radiologist to use for radiological interpretation.

DICOM part 14: GSDF-calibrated medical grade monitor vs a DICOM part 14: GSDF-calibrated "commercial off-the-shelf" (COTS) monitor for viewing 8-bit dental images

OBJECTIVES

To investigate whether there is any difference in the presented image quality between a medical grade monitor and a "commercial off-the- shelf" (COTS) monitor when displaying an 8-bit dental image.

METHODS

The digital imaging and communications in medicine (DICOM) part 14: greyscale standard display function (GSDF) was verified for both monitors. A visual grading characteristics (VGC) curve was constructed to measure the difference in image quality between the two monitors by comparing radiological structures displayed on each monitor with a DICOM part 14: GSDF-calibrated laptop monitor as reference.

RESULTS

All of the monitors conformed to within the American Association of Physicists in Medicine Task Group 18 10% tolerance levels for the assessment of the DICOM part 14: GSDF. There was no difference in the preferred perceived visual sensation for the displayed image between the two tested monitors with the area under the VGC curve = 0.53 and 95% confidence interval = 0.47-0.59.

CONCLUSIONS

A DICOM part 14: GSDF COTS monitor is capable of displaying an image quality that is equally preferred to a DICOM part 14: GSDF medical grade monitor for an 8-bit image file.

Technical and radiological image quality comparison of different liquid crystal displays for radiology

BACKGROUND

To inform cost-effective decisions in purchasing new medical liquid crystal displays, we compared the image quality in displays made by three manufacturers.

METHODS

We recruited 19 radiologists and residents to compare the image quality of four liquid crystal displays, including 3-megapixel Barco(®), Eizo(®), and NEC(®) displays and a 6-megapixel Barco display. The evaluators were blinded to the manufacturers' names. Technical assessments were based on acceptance criteria and test patterns proposed by the American Association of Physicists in Medicine. Radiological assessments were performed on images from the American Association of Physicists in Medicine Task Group 18. They included X-ray images of the thorax, knee, and breast, a computed tomographic image of the thorax, and a magnetic resonance image of the brain. Image quality was scored on an analog scale (range 0-10). Statistical analysis was performed with repeated-measures analysis of variance.

RESULTS

The Barco 3-megapixel display passed all acceptance criteria. The Eizo and NEC displays passed the acceptance criteria, except for the darkest pixel value in the grayscale display function. The Barco 6-megapixel display failed criteria for the maximum luminance response and the veiling glare. Mean radiological assessment scores were 7.8±1.1 (Barco 3-megapixel), 7.8±1.2 (Eizo), 8.1±1.0 (NEC), and 8.1±1.0 (Barco 6-megapixel). No significant differences were found between displays.

CONCLUSION

According to the tested criteria, all the displays had comparable image quality; however, there was a three-fold difference in price between the most and least expensive displays.

Evaluation of low-cost telemammography screening configurations: a comparison with film-screen readings in vulnerable areas

The aim of this study was to evaluate the diagnostic accuracy for detecting breast cancer using different telemammography configurations, including combinations of both low-cost capture devices and consumer-grade color displays. At the same time, we compared each of these configurations to film-screen readings. This study used a treatment-by-reader-by-case factorial design. The sample included 70 mammograms with 34 malignant cases. The readers consisted of four radiologists who classified all of the cases according to the categories defined by the Breast Imaging Reporting and Data System (BI-RADS). The evaluated capture devices included a specialized film digitizer and a digital camera, and the evaluated displays included liquid crystal display (LCD) and light-emitting diode (LED) consumer-grade color displays. Receiver operating characteristic curves, diagnostic accuracy (measured as the area under these curves), accuracy of the composition classification, sensitivity, specificity, and the degree of agreement between readers in the detection of malignant cases were also evaluated. Comparisons of diagnostic accuracy between film-screen and the different combinations of digital configurations showed no significant differences for nodules, calcifications, and asymmetries. In addition, no differences were observed in terms of sensibility or specificity when the degree of malignancy using the film-screen method was compared to that provided with digital configurations. Similar results were observed for the classification of breast composition. Furthermore, all observed reader agreements of malignant detection between film-screen and digital configurations were substantial. These findings indicate that the evaluated digital devices showed comparable diagnostic accuracy to the reference treatment (film-screen).

Diagnostic accuracy of digitized chest X-rays using consumer-grade color displays for low-cost teleradiology services: a multireader-multicase comparison

INTRODUCTION

In teleradiology services and in hospitals, the extensive use of visualization displays requires affordable devices. The purpose of this study was to compare three differently priced displays (a medical-grade grayscale display and two consumer-grade color displays) for image visualization of digitized chest X-rays.

MATERIALS AND METHODS

The evaluated conditions were interstitial opacities, pneumothorax, and nodules using computed tomography as the gold standard. The comparison was accomplished in terms of receiver operating characteristic (ROC) curves, the diagnostic power measured as the area under ROC curves, accuracy in conditions classification, and main factors affecting accuracy, in a factorial study with 76 cases and six radiologists.

RESULTS

The ROC curves for all of the displays and pathologies had similar shapes and no differences in diagnostic power. The proportion of cases correctly classified for each display was greater than 71.9%. The correctness proportions of the three displays were different (p<0.05) only for interstitial opacities. The evaluation of the main factors affecting these proportions revealed that the display factor was not significant for either nodule size or pneumothorax size (p>0.05).

CONCLUSIONS

Although the image quality variables showed differences in the radiologists' perceptions of the image quality of the three displays, significant differences in the accuracy did not occur. The main effect on the variability of the proportions of correctly classified cases did not come from the display factor. This study confirms previous findings that medical-grade displays could be replaced by consumer-grade color displays with the same image quality.

Evaluation of three pneumothorax size quantification methods on digitized chest X-ray films using medical-grade grayscale and consumer-grade color displays

This study focused on the effects of pneumothorax size quantification in digital radiology environments when a quantification method is selected according to the radiologist's criteria. The objective of this study was to assess the effects of factors, including the radiologist (with different experience), displays (medical-grade and consumer-grade displays), or display calibration, on the Rhea, Collins, and Light quantification methods. This study used a factorial design with 76 cases, including 16 pneumothorax cases observed by six radiologists on three displays with and without the DICOM standard calibration. The gold standard was established by two radiologists by using computed tomography. Analysis of variance (ANOVA) was performed on the pneumothorax sizes. For the three quantifications methods, none of the evaluated factors were significant. We conclude that radiologists, displays, and calibration do not significantly affect the quantification of pneumothorax size in different digital radiology environments.

Medical imaging displays and their use in image interpretation

The adequate and repeatable performance of the image display system is a key element of information technology platforms in a modern radiology department. However, despite the wide availability of high-end computing platforms and advanced color and gray-scale monitors, the quality and properties of the final displayed medical image may often be inadequate for diagnostic purposes if the displays are not configured and maintained properly. In this article-an expanded version of the Radiological Society of North America educational module "Image Display"-the authors discuss fundamentals of image display hardware, quality control and quality assurance processes for optimal image interpretation settings, and parameters of the viewing environment that influence reader performance. Radiologists, medical physicists, and other allied professionals should strive to understand the role of display technology and proper usage for a quality radiology practice. The display settings and display quality control and quality assurance processes described in this article can help ensure high standards of perceived image quality and image interpretation accuracy.

Observer performance using virtual pathology slides: impact of LCD color reproduction accuracy

The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its "native" off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.

Prediction of human observer performance in a 2-alternative forced choice low-contrast detection task using channelized Hotelling observer: impact of radiation dose and reconstruction algorithms

PURPOSE

Efficient optimization of CT protocols demands a quantitative approach to predicting human observer performance on specific tasks at various scan and reconstruction settings. The goal of this work was to investigate how well a channelized Hotelling observer (CHO) can predict human observer performance on 2-alternative forced choice (2AFC) lesion-detection tasks at various dose levels and two different reconstruction algorithms: a filtered-backprojection (FBP) and an iterative reconstruction (IR) method.

METHODS

A 35 × 26 cm(2) torso-shaped phantom filled with water was used to simulate an average-sized patient. Three rods with different diameters (small: 3 mm; medium: 5 mm; large: 9 mm) were placed in the center region of the phantom to simulate small, medium, and large lesions. The contrast relative to background was -15 HU at 120 kV. The phantom was scanned 100 times using automatic exposure control each at 60, 120, 240, 360, and 480 quality reference mAs on a 128-slice scanner. After removing the three rods, the water phantom was again scanned 100 times to provide signal-absent background images at the exact same locations. By extracting regions of interest around the three rods and on the signal-absent images, the authors generated 21 2AFC studies. Each 2AFC study had 100 trials, with each trial consisting of a signal-present image and a signal-absent image side-by-side in randomized order. In total, 2100 trials were presented to both the model and human observers. Four medical physicists acted as human observers. For the model observer, the authors used a CHO with Gabor channels, which involves six channel passbands, five orientations, and two phases, leading to a total of 60 channels. The performance predicted by the CHO was compared with that obtained by four medical physicists at each 2AFC study.

RESULTS

The human and model observers were highly correlated at each dose level for each lesion size for both FBP and IR. The Pearson's product-moment correlation coefficients were 0.986 [95% confidence interval (CI): 0.958-0.996] for FBP and 0.985 (95% CI: 0.863-0.998) for IR. Bland-Altman plots showed excellent agreement for all dose levels and lesions sizes with a mean absolute difference of 1.0% ± 1.1% for FBP and 2.1% ± 3.3% for IR.

CONCLUSIONS

Human observer performance on a 2AFC lesion detection task in CT with a uniform background can be accurately predicted by a CHO model observer at different radiation dose levels and for both FBP and IR methods.

ROCView: prototype software for data collection in jackknife alternative free-response receiver operating characteristic analysis

ROCView has been developed as an image display and response capture (IDRC) solution to image display and consistent recording of reader responses in relation to the free-response receiver operating characteristic paradigm. A web-based solution to IDRC for observer response studies allows observations to be completed from any location, assuming that display performance and viewing conditions are consistent with the study being completed. The simplistic functionality of the software allows observations to be completed without supervision. ROCView can display images from multiple modalities, in a randomised order if required. Following registration, observers are prompted to begin their image evaluation. All data are recorded via mouse clicks, one to localise (mark) and one to score confidence (rate) using either an ordinal or continuous rating scale. Up to nine "mark-rating" pairs can be made per image. Unmarked images are given a default score of zero. Upon completion of the study, both true-positive and false-positive reports can be downloaded and adapted for analysis. ROCView has the potential to be a useful tool in the assessment of modality performance difference for a range of imaging methods.

Optimizing the pathology workstation "cockpit": Challenges and solutions

The 21(st) century has brought numerous changes to the clinical reading (i.e., image or virtual pathology slide interpretation) environment of pathologists and it will continue to change even more dramatically as information and communication technologies (ICTs) become more widespread in the integrated healthcare enterprise. The extent to which these changes impact the practicing pathologist differ as a function of the technology under consideration, but digital "virtual slides" and the viewing of images on computer monitors instead of glass slides through a microscope clearly represents a significant change in the way that pathologists extract information from these images and render diagnostic decisions. One of the major challenges facing pathologists in this new era is how to best optimize the pathology workstation, the reading environment and the new and varied types of information available in order to ensure efficient and accurate processing of this information. Although workstations can be stand-alone units with images imported via external storage devices, this scenario is becoming less common as pathology departments connect to information highways within their hospitals and to external sites. Picture Archiving and Communications systems are no longer confined to radiology departments but are serving the entire integrated healthcare enterprise, including pathology. In radiology, the workstation is often referred to as the "cockpit" with a "digital dashboard" and the reading room as the "control room." Although pathology has yet to "go digital" to the extent that radiology has, lessons derived from radiology reading "cockpits" can be quite valuable in setting up the digital pathology reading room. In this article, we describe the concept of the digital dashboard and provide some recent examples of informatics-based applications that have been shown to improve the workflow and quality in digital reading environments.