MRI characteristics associated with high-grade myxoid liposarcoma.

AIM: To identify magnetic resonance imaging (MRI) features differentiating high-grade (>5% round-cell component) from low-grade myxoid liposarcomas (LPS) (≤5% round-cell component). MATERIALS AND METHODS: Informed consent was waived. Patients with myxoid LPS and MRI before biopsy, neoadjuvant therapy, and surgery were included retrospectively. High-grade components were recorded from histological specimens by a pathologist (24 years of experience). Images were evaluated by a senior radiologist (>12 years of experience) for tumour size, location, tissue layer, and MRI features (signal intensity, heterogeneity, margin, and perilesional characteristics). Descriptive statistics, Fisher's exact test to identify associations with a round-cell component, and multivariate logistic regression to identify independent predictors of high-grade tumours were used. RESULTS: Thirty-one patients (16 women [mean 51.1 years; range 19-79 years] and 15 men [mean 45.5 years; range 18-95 years]) with myxoid LPS (23 low-grade, eight high-grade) were included. All high-grade lesions had lipid signal, a peritumoural capsule and peritumoural contrast enhancement, and more commonly exhibited heterogeneous signal; however, the average size of ≥10 cm was the strongest independent indicator of high-grade status (odds ratio [OR], 14.6; 95% confidence interval [CI]: 1.6, 131). CONCLUSION: Size ≥10 cm is most strongly associated with high-grade myxoid LPS (round-cell component >5%). Other features possibly differentiating high-grade from low-grade status include lesion margin, lipid signal, and perilesional characteristics.

Predictive role of imaging in sentinel lymph node dissection for melanoma.

A retrospective study of 67 patients with metastatic melanoma was performed to evaluate if imaging from lymphoscintigraphy could predict a higher miss rate if only the most radioactive node were removed. Following protocol for sentinel node biopsy, the surgeon resected all lymph nodes containing radioactivity > 10% of the most radioactive node. A correlation was performed between the radioactive counts of the lymph nodes and the presence of metastases. The percentage of cases in which the most radioactive node was negative for metastasis on pathology was calculated. Two nuclear medicine physicians read the images from lymphoscintigraphy specifically to determine if the first lymph node visualized became less intense than other nodes on later images. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. In 13 of 67 (19%) patients, the most radioactive lymph node was negative for metastasis while a less radioactive node contained metastatic disease. Consensus reading by the nuclear medicine physicians determined that in 9 cases, the first lymph node visualized became less intense than another lymph node on later images. Of the 9 cases, 4 were true positive and 5 were false positive when correlated with intraoperative count rate and pathology. Of the cases where the most radioactive node was not positive on histopathology (n = 13), the consensus reading by the nuclear medicine physicians reported 4 of them (31%). Imaging by lymphoscintigram had a sensitivity 31%, specificity 91%, positive predictive value 44%, and negative predictive value 85% for predicting whether the most radioactive lymph node at surgery would be negative for metastasis at pathology. We conclude that in patients with melanoma, lymphoscintigraphy has high specificity and negative predictive value but modest sensitivity and positive predictive value for detecting when the sentinel node will not be the most radioactive lymph node during sentinel lymph node dissection. These findings support that dynamic imaging by lymphoscintigraphy has a role in surgical planning but that the imaging protocol could benefit from further optimization.

Bayesian estimation of cerebral perfusion using reduced-contrast-dose dynamic susceptibility contrast perfusion at 3T.

BACKGROUND AND PURPOSE: DSC perfusion has been increasingly used in conjunction with other contrast-enhanced MR applications and therefore there is need for contrast-dose reduction when feasible. The purpose of this study was to establish the feasibility of reduced-contrast-dose brain DSC perfusion by using a probabilistic Bayesian method and to compare the results with the commonly used singular value decomposition technique. MATERIALS AND METHODS: Half-dose (0.05-mmol/kg) and full-dose (0.1-mmol/kg) DSC perfusion studies were prospectively performed in 20 patients (12 men; 34-70 years of age) by using a 3T MR imaging scanner and a gradient-EPI sequence (TR/TE, 1450/22 ms; flip angle, 90°). All DSC scans were processed with block circulant singular value decomposition and Bayesian probabilistic methods. SNR analysis was performed in both half-dose and full-dose groups. The CBF, CBV, and MTT maps from both full-dose and half-dose scans were evaluated qualitatively and quantitatively in both WM and GM on coregistered perfusion maps. Statistical analysis was performed by using a t test, regression, and Bland-Altman analysis. RESULTS: The SNR was significantly (P < .0001) lower in the half-dose group with 32% and 40% reduction in GM and WM, respectively. In the half-dose group, the image-quality scores were significantly higher in Bayesian-derived CBV (P = .02) and MTT (P = .004) maps in comparison with block circulant singular value decomposition. Quantitative values of CBF, CBV, and MTT in Bayesian-processed data were comparable and without a statistically significant difference between the half-dose and full-dose groups. The block circulant singular value decomposition-derived half-dose perfusion values were significantly different from those of the full-dose group both in GM (CBF, P < .001; CBV, P = .02; MTT, P = .02) and WM (CBF, P < .001; CBV, P = .003; MTT, P = .01). CONCLUSIONS: Reduced-contrast-dose (0.05-mmol/kg) DSC perfusion of the brain is feasible at 3T by using the Bayesian probabilistic method with quantitative results comparable with those of the full-dose protocol.

Telepathology overview: from concept to implementation.

Telepathology is the practice of pathology at a distance by using video imaging and telecommunications. Significant progress has been made in telepathology. To date, 12 classes of telepathology systems have been engineered. Rapid and ultrarapid virtual slide processors may further expand the range of telepathology applications. Next-generation digital imaging light microscopes, such as miniaturized microscope arrays (MMA), may make virtual slide processing a routine laboratory tool. Diagnostic accuracy of telepathology is comparable with that of conventional light microscopy for most diagnoses. Current telepathology applications include intraoperative frozen sections services, routine surgical pathology services, second opinions, and subspecialty consultations. Three telepathology practice models are discussed: the subspecialty practice (SSP) model; the case triage practice (CTP) model; and the virtual group practice (VGP) model. Human factors influence performance with telepathology. Experience with 500 telepathology cases from multiple organs significantly reduces the video viewing time per case (P < .01). Many technology innovations can be represented as S-curves. After long incubation periods, technology use and/or efficiency may accelerate. Telepathology appears to be following an S-curve for a technical innovation.

Dynamic-robotic telepathology: Department of Veterans Affairs feasibility study.

In this retrospective study, we assess the accuracy, confidence levels, and viewing times of two generalist pathologists using both dynamic-robotic telepathology and conventional light microscopy (LM) to render diagnoses on a test set of 100 consecutive routine surgical pathology cases. The objective is to determine whether telepathology will allow a pathology group practice at a diagnostic hub to provide routine diagnostic services to a remote hospital without an on-site pathologist. For TP, glass slides were placed on the motorized stage of the robotic microscope of a telepathology system by a senior laboratory technologist in Iron Mountain, MI. Real-time control of the motorized microscope was then transferred to a pathologist in Milwaukee, WI, who viewed images of the glass slides on a video monitor. The telepathologists deferred rendering a diagnosis in 1.5% of cases. Clinically important concordance between the individual diagnoses rendered by telepathology and the "truth" diagnoses established by rereview of glass slides was 98.5%. In the telepathology mode, there were five incorrect diagnoses out of a total of 197 diagnoses. In four cases in which the telepathology diagnosis was incorrect, the pathologist's diagnosis by LM was identical to that rendered by telepathology. These represent errors of interpretation and cannot be ascribed to telepathology. The certainty of the pathologists with respect to their diagnoses was evaluated over time. Results for the first 50 cases served as baseline data. For the second 50 cases, confidence in rendering a diagnosis in the telepathology mode was essentially identical to that of making a diagnosis in the LM viewing mode. Viewing times in the telepathology mode also improved with more experience using the telepathology system. These results support the concept that an off-site pathologist using dynamic-robotic telepathology can substitute for an on-site pathologist as a service provider.

Diagnostic accuracy of an international static-imaging telepathology consultation service.

Static-image and dynamic- (real-time) image telepathology are competing technologies. Although some studies suggest that the diagnostic accuracy of the dynamic-image telepathology approaches the accuracy of light microscopy, few reports have documented the diagnostic accuracy of static-image telepathology as used in the setting of an actual surgical pathology consultation practice. We report the results of an analysis of 171 telepathology consultation cases submitted to the Arizona-International Telemedicine Network (AITN). Digital images were submitted by pathologists from six participating institutions in Arizona, Mexico, and China. Telepathologists could render a telepathology diagnosis (TP) or defer rendering a diagnosis to obtain additional video images, glass slides for detailed analysis, or to obtain tissue blocks for special studies such as immunohistochemistry. The telepathologists rendered diagnoses for 144 cases and deferred 27 cases. Two pathologists retrospectively evaluated-glass slides from each case and rendered a consensus glass slide (GS) "truth" diagnosis. There was 88.2% concordance between TP and GS diagnoses (127 of 144 diagnoses). Concordance of 96.5% was achieved for clinically important diagnoses (139 of 144 diagnoses). Telepathologists deferred making a diagnosis to obtain glass slides for conventional light microscopy in 14 cases (8.1%) and for results of immunohistochemistry studies in 13 cases (7.6%). Thus, correct diagnoses were rendered by static-image telepathology in 127 of 171 cases (74.3%) at the time of telepathology diagnostic sessions. Inappropriate field selection and sampling biases of referring pathologists, as well as a tendency of static-image telepathologists to underestimate the complexity of some cases, may reduce the value of consultations based on the viewing of static images.

Computer-displayed eye position as a visual aid to pulmonary nodule interpretation.

Approximately 30% of nodules are missed during the initial reading of chest radiographs. Eye-position recordings have shown that most nodules that are missed receive prolonged visual attention. A computer algorithm was developed that uses eye-position and gaze-duration times to identify locations on the chest image likely to contain missed nodules. These locations are highlighted on the displayed image to give visual feedback. The current study tested whether visual feedback was an effective aid to nodule detection. Six radiology residents searched 40 chest images for nodules while their eye-position and gaze-duration times were recorded. Half received displayed visual feedback and half were given a second view without feedback. Two months later the two groups returned and viewed the images in the opposite condition to counterbalance for possible practice effects. Performance of readers who were given feedback showed an average of 16% improvement as measured by the alternative free response operating characteristic (AFROC) curve area, A1. Performance of the same readers given a second look without feedback did not improve.

Searching for lung nodules. Visual dwell indicates locations of false-positive and false-negative decisions.

Eye position recordings made while radiologists searched chest images for lung nodules showed that regions falsely reported positive or suspicious received prolonged visual attention. Correlation of regional fixation dwell time with independent ratings of image features indicated that more than 90% of false-positive decisions were caused by some perturbation in the image that aroused the suspicion of the viewer. The remainder apparently arose from within the viewer. Most missed nodules (false-negative reports) also received prolonged visual attention, implying an active decision not to perceive a nodule. The data are interpreted to show that roughly one task-related decision is made during each second of scanning a radiograph. This departs from the central assumption of the traditional signal-detection model based upon one decision per image.

A perceptually based method for enhancing pulmonary nodule recognition.

RATIONALE AND OBJECTIVES: Feedback of chest areas receiving prolonged gaze durations significantly increases nodule detection performance. Why feedback circling enhances performance when other cueing methods produce equivocal results was assessed. METHODS: Chest and noise images with nodule targets were used to determine: what type of cue is most effective; whether circling influences the way the eye samples the target; whether circling limits processing of distracting information outside its boundary. RESULTS: Circling improves performance more than cues with less complete boundaries and increases the accuracy and frequency with which nodules are fixated. Outside distractors were detected less often with than without the circle present. CONCLUSIONS: Circling isolates the abnormal region from the rest of the image, making disembedding and integration of nodule features more likely and insulates this region from distractors. The facilitative effects of circling are generalizable to other images in which low contrast targets are embedded in noisy backgrounds.

Receiver operating characteristic evaluation of computer display of adult portable chest radiographs.

RATIONALE AND OBJECTIVES: The suitability of using an image console monitor for interpretation of adult portable chest radiographs was evaluated with receiver operating characteristic (ROC) analysis and subjective techniques. METHODS: Radiologists read 80 chest images, once on a display monitor and once on computed radiography film, for the presence or absence of pneumothorax or atelectasis. Judgments of correct or incorrect positions of tubes and lines were reported, and total viewing time was recorded. RESULTS: A statistically significant difference was found in favor of monitor reading for detection of pneumothoraces. Atelectasis detection also was higher with monitor reading, but the difference did not reach statistical significance. Tube/line judgments were equivalent for both modes. Total viewing time was approximately 1 minute longer per image with the monitor. CONCLUSIONS: Viewing computed radiography images on a workstation monitor does not seem to affect diagnostic accuracy compared with film viewing. Preset image defaults tailored to the individual radiologist could decrease total viewing time to acceptable levels.

Comparison of eye position versus computer identified microcalcification clusters on mammograms.

The purpose of this study was to compare identifications of microcalcification clusters on mammograms by a computerized detection scheme and by human observers having their eye position recorded. Eighty digitized mammograms (half with a subtle microcalcification cluster) were analyzed by a computerized detection scheme and then were read from laser-printed films by six mammographers while eye position was recorded. The computer had 83% true positives with a false-positive rate of 0.5 per image. The true positives of the radiologists ranged from 78% to 90%, with false-positive rates ranging from 0.03 to 0.20. Locations of true and false positives identified by computer and by the human were compared. All but 5% of the true clusters were identified by either the computer, human, or by both. Here 10% of the clusters were detected by only the computer, and 11% were missed by the computer but detected by at least one radiologist. False positives were of three types: identified by computer only, by the human reader only, or by both. Eye-position data indicated significant differences in dwell time between both true-positive and false-positive locations reported by the radiologist versus the computer detections. A follow-up analysis indicated that microcalcification clusters and false positives were judged to have more identifiable characteristics of true calcifications and were associated with longer gaze durations than those with fewer microcalcification characteristics. In general, the computer was able to detect clusters judged to have few or no features that the radiologists were not able to detect. Comparison of computer versus human identification of microcalcification clusters may be useful for improving computerized detection schemes to serve as clinical aids to mammographers, and for understanding what image features lead to false-positive decisions for both the computer and the human reader.

Clinical assessment of dry laser-processed film versus traditional wet-processed film with computed tomography, magnetic resonance imaging, and ultrasound.

RATIONALE AND OBJECTIVES: To compare image quality and diagnostic performance (by using receiver operating characteristic techniques) for laser imaging film from two systems: a traditional wet system that uses chemical processing and a new dry system that is wet-chemistry-free. METHODS: For three separate studies (computed tomography, magnetic resonance imaging, and ultrasound), identical images for 40 cases were printed on both the wet and dry imaging systems. Ten radiologists participated in each study, giving a decision confidence rating for lesion present or absent and evaluating image quality. RESULTS: In all three studies, there were no statistically significant differences in diagnostic performance when reading images that had been wet processed versus those that had been dry processed. Image quality was comparable for wet-and dry-processed films for all three modalities. CONCLUSION: Dry laser processing produces high-quality radiologic films that are comparable to those currently produced by using wet laser processing. Dry-processed film represents a useful alternative to wet-processed film.

Visual scanning patterns of radiologists searching mammograms.

RATIONALE AND OBJECTIVES: I examined whether the principles of search, detection, and decision making described for pulmonary nodule detection can be applied to lesion detection in mammographic images. METHODS: The eye position of six radiologists (three staff mammographers and three radiology residents) was recorded as they searched mammograms for masses and microcalcifications. RESULTS: True- and false-positive decisions were associated with prolonged gaze durations; false-negative decisions were associated with longer gaze durations than true-negatives. Readers with more experience tended to detect lesions earlier in the search than did readers with less experience, but those with less experience tended to spend more time overall searching the images and cover more image area than did those with more experience. CONCLUSION: Gaze duration is a useful predictor of missed lesions in mammography, making gaze duration a potential tool for perceptual feedback. Mammographic search for readers with different degrees of experience can be characterized by gaze durations, scan paths, and detection times.

The influence of a perceptually linearized display on observer performance and visual search.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether perceptual linearization of the tone scale affects the detection and visual search behaviors of radiologists searching mammograms for masses and microcalcifications. A perceptually linearized display is designed to match the capabilities of the human visual system more closely than a nonlinearized display. MATERIALS AND METHODS: Six radiologists viewed 50 pairs of mammograms, once on a perceptually linearized cathode-ray tube (CRT) monitor and once on a non-linearized CRT monitor. Eye position also was recorded as the observers searched the images for masses and microcalcifications. RESULTS: Observer performance was significantly (P = .003) better with the perceptually linearized display. Dwell times associated with true-negative decisions were significantly longer with use of the nonlinearized display. The number of fixation clusters generated during search was also greater with use of the nonlinearized display for the lesion-free images. CONCLUSION: A perceptually linearized display yields better detection performance and a more efficient visual search. Perceptually linearized displays should be used for reading radiographs displayed on CRT monitors.

Observer detection performance in radiology using a retransmission-free network communication protocol.

RATIONALE AND OBJECTIVES: We measured the effect of image data loss on diagnostic accuracy to test the possibility of using a retransmission-free network communication protocol for transferring radiologic images. METHODS: Mammograms transferred over a simulated network with 0%, 15%, and 25% transmission packet loss were presented randomly to 10 observers who typically read mammograms. Observers reported on the presence or absence of microcalcification clusters and the number of calcifications per cluster. RESULTS: Performance with 15% loss did not differ from performance with 0% loss. The 25% loss condition resulted in a significant decrease in performance. Accuracy of counting individual microcalcifications was high in all three loss conditions. CONCLUSION: Up to 15% packet loss can be tolerated without affecting diagnostic performance. These data suggest that in some radiologic applications retransmission-free communication protocols may be useful.

Perceptual skill, radiology expertise, and visual test performance with NINA and WALDO.

RATIONALE AND OBJECTIVES: The goal of this study was to determine if radiologists possess superior visual search and analysis skills compared with those of laypeople. MATERIALS AND METHODS: In two experiments, radiologists and laypeople searched one of two complex pictorial scenes for hidden targets. Eye position was recorded during the search. Two measures of performance were obtained: accuracy of detecting targets as measured by using alternative free response receiver operating characteristic analysis and visual search efficiency as measured by using eye position analysis. RESULTS: There were no statistically significant differences in detection performance between radiologists and laypeople for either of the search tasks. Radiologists took longer on average to search the images and to first fixate on the targets than did the laypeople. For both groups, true-positive and false-positive decisions were associated with longer dwell times than true-negative decisions. As with radiology search tasks, false-negative decisions were also associated with longer dwell times than true-negative decisions. CONCLUSION: Performance on two visual search and detection tasks indicate that radiologists do not possess superior visual skills compared with laypeople. Radiology expertise is more likely to be a combination of specific visual and cognitive skills derived from medical training and experience in detecting and determining the diagnostic importance of radiographic findings.

Differences in time to interpretation for evaluation of bone radiographs with monitor and film viewing.

RATIONALE AND OBJECTIVES: The authors evaluated how observers search hard-copy versus soft-copy images to determine why viewing times are longer for images displayed on a monitor. METHODS: Twenty-seven nonconsecutive bone-trauma computed radiographs were collected from the routine emergency practice. Eye positions of three bone radiologists and three orthopedic surgeons were recorded as they searched images on a view box and digital images at a workstation. RESULTS: Overall viewing time was longer for images displayed on a monitor. Time to first fixate a lesion and true-negative dwell times were significantly longer with the monitor than with the film. Absolute numbers of clusters and dwell times were greater for diagnostic image areas on the monitor than on the film. Twenty percent of the clusters for images viewed on the monitor were on the image-processing menu. CONCLUSION: The amount and type of information that is processed during search is different when images are viewed on a monitor rather than on film.

Observer performance comparison of digital radiograph systems for stereotactic breast needle biopsy.

RATIONALE AND OBJECTIVES: Two digital radiograph systems for stereotactic mammography, one using a lens to couple a Lanex Regular screen to a back-illuminated charge-coupled device (CCD) and one using a fiber-optic taper to couple a Min-R Regular-type screen to a front-illuminated CCD, were evaluated with respect to observer performance. METHODS: A contrast-detail phantom was imaged in a variety of equivalent exposure conditions on both systems. Six observers viewed images on a video monitor and recorded which objects were detected. RESULTS: Performance (percent correct detections) with the lens-coupled system using the Lanex Regular screen was significantly higher than with the fiber-optic-coupled system using the Min-R Regular-type screen. CONCLUSION: Differences in absorption efficiencies of phosphors used, as well as differences in design of the two cameras, can explain differences in observer detection performance.

Reduction of patient exposure in pediatric radiology.

RATIONALE AND OBJECTIVES: The authors determined whether presently used exposure levels in pediatric imaging can be reduced without loss of information or a decrease in diagnostic accuracy. MATERIALS AND METHODS: Multiple (stacked) image detectors and filters were used to obtain identical compute radiographic images at different exposure levels of neonates with either no active lung disease or hyaline membrane disease. Physical characteristics of the images were measured. A contrast-detail study and a receiver operating characteristic study were conducted to measure observer performance. RESULTS: Physical measurements and results of the contrast-detail study revealed that the dose-reduction images were essentially limited by x-ray quantum noise. Results of the receiver operating characteristic study indicated that diagnostic accuracy did not decrease significantly up to about 75% exposure reduction levels, although image quality rating data decreased with each exposure reduction. CONCLUSION: Decreasing exposure levels to about 75% of current levels may be acceptable in some clinical situations where dose is a concern, such as in pediatric imaging.

Comparison of conventional and computed radiography: assessment of image quality and reader performance in skeletal extremity trauma.

RATIONALE AND OBJECTIVES: Reader performance and image quality wee assessed for standard film, computed film, and computer monitor radiography viewing formats in the evaluation of skeletal extremity trauma. MATERIALS AND METHODS: Three radiologists and three orthopedic surgeons interpreted 27 skeletal radiographs obtained with equivalent technical parameters. Readers evaluated standard film, computed film, and computer monitor formats randomly for fracture and soft-tissue abnormalities. Sessions were videotaped, and eye motion was recorded. RESULTS: No statistically significant differences were found between image formats for true-positive or false-positive findings of trauma indicators. Findings were classified as false-negative based on eye position fixation times. Search errors (lesion not fixated) accounted for 21.7%, 20.6% and 17.1% of false-negative errors with the computer monitor, computed film, and standard film formats, respectively. Combined recognition errors and decision errors were 78.3%, 79.4%, and 82.9%, respectively. Viewing times were longest for the computer monitor images (P < .001). Image quality, contrast, and sharpness were rated highest for computed radiographs (P = .001). Radiologists had a higher true-positive decision rate than orthopedic surgeons (P = .03). CONCLUSION: No statistically significant differences were seen in reader performance among viewing formats. The computed film format received the highest quality rating, and workstation viewing times were longest.