Michael G. Evanoff

Ambient Lighting: Effect of Illumination on Soft-Copy Viewing of Radiographs of the Wrist

OBJECTIVE The aim of the work was to establish optimum ambient light conditions for viewing radiologic images of the wrist on liquid crystal display monitors. MATERIALS AND METHODS Five ambient light levels were investigated: 480, 100, 40, 25, and 7 lux. Seventy-nine experienced radiologists were asked to examine 30 posteroanterior wrist images and decide whether a fracture was present. All images were displayed on liquid crystal display monitors. Receiver operating characteristic analysis was performed, and the numbers of false-positive and false-negative findings were recorded. RESULTS For all the radiologists, greater area under the receiver operating characteristic curve and lower numbers of false-positive and false-negative findings were recorded at 40 and 25 lux compared with 480 and 100 lux. At 7 lux, the results were generally similar to those at 480 and 100 lux. The experience and knowledge of radiologists specializing in imaging of musculoskeletal trauma appeared to compensate in part for inappropriate lighting levels. CONCLUSION Typical office lighting and current recommendations on ambient lighting can reduce diagnostic efficacy compared with lower levels of ambient lighting. If, however, no light other than that of the monitor is used, results are similar to those with excessive levels of lighting. Careful control of ambient lighting is therefore required to ensure that diagnostic accuracy is maximized, particularly for clinicians not expert in interpreting posteroanterior wrist images.

Diagnostic Efficacy of Handheld Devices for Emergency Radiologic Consultation

OBJECTIVE Orthopedic injury and intracranial hemorrhage are commonly encountered in emergency radiology, and accurate and timely diagnosis is important. The purpose of this study was to determine whether the diagnostic accuracy of handheld computing devices is comparable to that of monitors that might be used in emergency teleconsultation. SUBJECTS AND METHODS Two handheld devices, a Dell Axim personal digital assistant (PDA) and an Apple iPod Touch device, were studied. The diagnostic efficacy of each device was tested against that of secondary-class monitors (primary class being clinical workstation display) for each of two image types-posteroanterior wrist radiographs and slices from CT of the brain-yielding four separate observer performance studies. Participants read a bank of 30 wrist or brain images searching for a specific abnormality (distal radial fracture, fresh intracranial bleed) and rated their confidence in their decisions. A total of 168 readings by examining radiologists of the American Board of Radiology were gathered, and the results were subjected to receiver operating characteristics analysis. RESULTS In the PDA brain CT study, the scores of PDA readings were significantly higher than those of monitor readings for all observers (p < or = 0.01) and for radiologists who were not neuroradiology specialists (p < or = 0.05). No statistically significant differences between handheld device and monitor findings were found for the PDA wrist images or in the iPod Touch device studies, although some comparisons approached significance. CONCLUSION Handheld devices show promise in the field of emergency teleconsultation for detection of basic orthopedic injuries and intracranial hemorrhage. Further investigation is warranted.

Flexible Image Evaluation: iPad versus Secondary-class Monitors for Review of MR Spinal Emergency Cases, A Comparative Study

RATIONALE AND OBJECTIVES Studies have highlighted the potential of handheld viewing devices for rapid diagnosis and increased smartphone usage among physicians and radiologists is known as is the clinical applicability of hand-held devices for computed tomography (CT) spinal injury cases. Magnetic resonance (MR), however, is the accepted gold standard for spinal imaging, providing visualization of both ligament and spinal cord pathology. This study investigated the diagnostic accuracy of the iPad, the most probable alternative display device outside the radiology environment and financially viable alternative, when reviewing emergency spinal MR images, in comparison with secondary-class LCD devices in the case of the interpretation of CT and MR imaging examinations. MATERIALS AND METHODS In total 31 MR cases including both positives (n = 13) containing one of four possible presentations: spinal cord compression, cauda equine syndrome, spinal cord hemorrhage, or spinal cord edema and controls (n = 18) were reviewed. Ziltron iPad software facilitated the display of cases and the receiver operating characteristic (ROC) analysis. Thirteen American Board of Radiology board-certified radiologists reviewed all cases on both displays. Standardized viewing conditions were maintained. RESULTS Dorfman-Berbaum-Metz multireader-multicase (DBM MRMC) analysis was performed including random readers/random cases, fixed readers/random cases and random readers/fixed cases. No differences of statistical significance (P ≤ .05) could be found in terms of area under the curve, sensitivity and specificity between the iPad and secondary-class display. CONCLUSION The iPad performed with equal diagnostic accuracy when compared with the secondary-class LCD device after DBM MRMC analysis, demonstrating the iPad as an option to aid initial review of MR spinal emergency cases.

A reduced contrast volume acquisition regimen based on cardiovascular dynamics improves visualisation of head and neck vasculature with carotid MDCT angiography

PURPOSE To investigate enhancement of head and neck arteries during carotid computed tomography angiography using a reduced volume contrast regimen and craniocaudal scan acquisition. MATERIALS AND METHODS Two hundred and two patients underwent carotid angiography using a 64 channel computed tomography scanner. Patients were allocated to one of two acquisition/contrast regimens: regimen A, the departments standard protocol, consisting of a caudocranial scan direction with 100mL of contrast intravenously; regimen B, involving a craniocaudal scan direction and approximately 50 mL of contrast using a timing dictated by patient hemodynamics. Attenuation profiles of cranial arteries and veins in 6 anatomical segments were assessed and arteriovenous contrast ratios (AVCR) calculated. Receiver operating characteristic (ROC) analysis was performed using DBM methodology. RESULTS Arterial attenuation was up to 54% (p<0.01) higher following regimen B compared with A. Attenuation in the veins were significantly lower in regimen B than in regimen A with a maximum reduction of up to 93% (p<0.0001). With regimen B, there were significant (p<0.0001) improvements in AVCR at a variety of anatomical sites. The ROC analysis demonstrated a significantly higher Az score for the novel regimen compared with regimen A (p<0.002) with inter-neuroradiologist agreement increasing from poor to moderate. CONCLUSION Significant improvements in visualisation of head and neck arterial vasculature can be achieved with a CT acquisition regimen using low contrast volume and injection timing based on patient specific contrast formula and craniocaudal scan direction.

Variations in performance of LCDs are still evident after DICOM gray-scale standard display calibration.

OBJECTIVE Quality assurance in medical imaging is directly beneficial to image quality. Diagnostic images are frequently displayed on secondary-class displays that have minimal or no regular quality assurance programs, and treatment decisions are being made from these display types. The purpose of this study is to identify the impact of calibration on physical and psychophysical performance of liquid crystal displays (LCDs) and the extent of potential variance across various types of LCDs. MATERIALS AND METHODS Three display types were evaluated from Hewlett Packard, Viewsonic, and NEC, which totalled 36 LCDs. These displays were calibrated to the DICOM gray scale standard display function using a VeriLum photometer and associated software under the same ambient room conditions. The American Association of Physicists in Medicine Task Group 18 test patterns were used to measure minimum and maximum luminance, contrast ratios, luminance response, veiling glare (physical and psychophysical), psychophysical noise, spatial resolution, and display uniformity. RESULTS Improvements after calibration were noted in all display types for luminance response and psychophysical evaluations of veiling glare. Minimum luminance, contrast ratios, and display uniformity improvements were noted in two separate display types. The only significant reduction in performance was noted for physical evaluations of veiling glare. CONCLUSION The data presented show that calibration has a significant impact on the brightness and contrast of displays, and other display parameters are influenced by this. The amount of variation in performance that was still evident after calibration is of concern.

Caudocranial scan direction and patient-specific injection protocols optimize ecg-gated and non-gated thoracic CTA

Objectives Caudocranial scan direction and contrast injection timing based on measured patient vessel dynamics can significantly improve artery opacification and reduce contrast dose in the assessment of acute aortic syndrome using gated and non–gated thoracic CTA. This study aimed to investigate enhancement of the thoracic aorta using caudocranial scan direction and a patient-specific contrast regimen. Methods Electrocardiogram–gated (n = 120) and non–gated (n = 200) thoracic computed tomography angiography was performed on patients with nontraumatic acute aortic syndrome. Patients were assigned to one of 2 acquisition/contrast regimens, namely, regimen A, craniocaudal scan direction with 120 mL contrast, and regimen B, caudocranial scan direction using a patient-specific contrast formula. Opacity of 9 arterial and venous segments was measured, arteriovenous contrast ratio calculated, and values compared using Mann-Whitney U statistics. Receiver operating characteristic analyses and visual grading characteristic assessed diagnostic efficacy and clinical image quality. Interobserver variations were investigated using &kgr; methods. Results Regimen B when compared to A, for both scanning/contrast techniques, demonstrated higher opacification in the aorta (P < 0.01) and lower opacification in the venous system (P < 0.0001). For protocol B, arteriovenous contrast ratio was significantly increased (P < 0.0001) and mean contrast volume reduced (P < 0.05) during gated [94 (10 mL)] and non–gated [78 (5 mL)] thoracic computed tomography angiography compared to A. Receiver operating characteristic analysis Az scores and interobserver agreement were significantly higher with regimen B than A (P < 0.05). Conclusions Caudocranial scan direction and injection timing based on patient-specific vessel dynamics can optimize artery opacification and diagnostic efficacy while reducing contrast volumes.

Number of mammography cases read per year is a strong predictor of sensitivity

Abstract. Early detection of breast cancers affects the 5-year recurrence rates and treatment options for diagnosed patients, and consequently, many countries have instituted nationwide screening programs. This study compared the performance of expert radiologists from Australia and the United States in detection of breast cancer. Forty-one radiologists, 21 from Australia and 20 from the United States, reviewed 30 mammographic cases containing two-view mammograms. Twenty cases had abnormal findings and 10 cases had normal findings. Radiologists were asked to locate malignancies and assign a level of confidence. A jackknife free-response receiver operating characteristic, figure of merit (JAFROC, FOM), inferred receiver operating characteristic, area under curve (ROC, AUC), specificity, sensitivity, and location sensitivity were calculated using Ziltron software and JAFROC v4.1. A Mann-Whitney U test was used to compare the performance of Australian and U.S. radiologists. The results showed that when experience and the number of mammograms read per year were taken into account, the Australian radiologists sampled showed significantly higher sensitivity and location sensitivity (p≤0.001). JAFROC (FOM) and inferred ROC (AUC) analysis showed no difference between the overall performance of the two countries. ROC (AUC) and location sensitivity were higher for the Australian radiologists who read the most cases per year.

The effect of JPEG2000 compression on detection of skull fractures.

RATIONAL AND OBJECTIVES To investigate the effect of the Joint Photographic Experts Group (JPEG2000) 30:1 and 60:1 lossy compression on the detection of cranial vault fractures when compared to JPEG2000 lossless compression. MATERIALS AND METHODS Fifty cranial computed tomography (CT) images were processed with three different level of JPEG2000 compression (lossless, 30:1 lossy, and 60:1 lossy) creating three sets of images. These were presented to five musculoskeletal specialists and five neuroradiologists. Each reader read at two of the three compression levels. Twenty-two cases contained a single fracture; the remaining 28 cases contained no fractures. Observers were asked to identify the presence or absence of a fracture, to locate its site, and rate their degree of confidence. Receiver operating characteristic (ROC), jackknife free-response receiver operating characteristic (JAFROC) and the Dorfman-Berbaum-Metz multiple reader multiple case (DBM-MRMC) analyses were used to explore differences between the lossless and lossy compressed images. RESULTS JPEG2000 lossless and 30:1 lossy compression demonstrated no significant difference in their performance with JAFROC and DBM-MRMC analysis (P < .416); however, JPEG2000 30:1 lossy compression demonstrated significantly better performance than 60:1 lossy compression (P < .016). A significant increase in misplaced confidence ratings was also seen with 60:1 (P < .037) over 30:1 lossy and lossless compression. CONCLUSION JPEG2000 60:1 compression degrades the detection of skull fractures significantly while increasing the confidence with which readers rate fractures compared with 30:1 lossy and lossless compression. JPEG2000 30:1 lossy compression does not significantly change performance when compared to JPEG2000 lossless for the detection of skull fractures on CT.

Evaluation of Off-the-Shelf Displays for Use in the American Board of Radiology Maintenance of Certification Examination

PURPOSE To prospectively compare high-, mid-, and low-resolution off-the-shelf displays currently employed by commercial testing centers, in terms of visibility of lesion features needed to render a diagnostic decision when possible diagnoses are provided in a multiple-choice format during a maintenance of certification (MOC) examination. MATERIALS AND METHODS The Psychometrics Division of the American Board of Radiology (ABR) approved the studies (human subjects and HIPAA compliant). One study compared 1280 x 1024 displays with 1024 x 768 displays; the second, 1600 x 1200 with 1280 x 1024 displays. Images from nine subspecialties were used. In each study, observers viewed images twice-once on each display. Diagnoses were provided, and observers rated visibility of diagnostic features. RESULTS Of 7977 data pairs analyzed in study 1, the 1024 and 1280 displays received the same ratings for 5726 data pairs (72% of the time), with the 1024 display receiving a higher rating for 679 data pairs (9% of the time) and the 1280 receiving a higher rating for 1572 data pairs (19% of the time) (P < .0001). When rating differences existed, all subspecialties except nuclear medicine had significantly more high-visibility ratings with the 1280 display. Of 1090 data pairs analyzed in study 2, the 1280 and 1600 displays received the same ratings for 689 data pairs (63% of the time), with the 1280 receiving a higher rating for 162 data pairs (15% of the time) and the 1600 receiving a higher rating for 239 data pairs (22% of the time) (P = .0001). When rating differences existed, only cardiopulmonary and musculoskeletal images had significantly more high-visibility ratings with the 1600 display. CONCLUSION For the ABR MOC examinations, 1280 x 1024 displays should be used, compared to 1024 x 768 displays; 1600 x 1200 displays may be necessary for some images. Good-quality images must be used on the examinations, so digital rather than digitized film images should be used to ensure high-quality images.

Calibration of medium-resolution monochrome cathode ray tube displays for the purpose of board examinations.

This report discusses calibration and set-up procedures for medium-resolution monochrome cathode ray tubes (CRTs) taken in preparation of the oral portion of the board examination of the American Board of Radiology (ABR). The board examinations took place in more than 100 rooms of a hotel. There was one display-station (a computer and the associated CRT display) in each of the hotel rooms used for the examinations. The examinations covered the radiologic specialties cardiopulmonary, musculoskeletal, gastrointestinal, vascular, pediatric, and genitourinary. The software used for set-up and calibration was the VeriLUM 4.0 package from Image Smiths in Germantown, MD. The set-up included setting minimum luminance and maximum luminance, as well as positioning of the CRT in each examination room with respect to reflections of roomlights. The calibration for the grey scale rendition was done meeting the Digital Imaging and communication in Medicine (DICOM) 14 Standard Display Function. We describe these procedures, and present the calibration data in tables and graphs, listing initial values of minimum luminance, maximum luminance, and grey scale rendition (DICOM 14 standard display function). Changes of these parameters over the duration of the examination were observed and recorded on 11 monitors in a particular room. These changes strongly suggest that all calibrated CRTs be monitored over the duration of the examination. In addition, other CRT performance data affecting image quality such as spatial resolution should be included in set-up and image quality-control procedures.