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.

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.

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.

Enhanced visualization processing: effect on workflow.

RATIONALE AND OBJECTIVES: Soft-copy viewing of digital radiographs allows for image processing to improve visualization of anatomy and lesions, but it can take more time than film-based viewing. Enhanced visualization processing (EVP) was developed to increase the latitude of an image without reducing the vital contrast, potentially reducing the need for the radiologist to manipulate images. This study examined the influence of processing radiographic images with EVP on workflow in a picture archiving and communications system (PACS). MATERIALS AND METHODS: Portable computed radiographic chest images were obtained and processed either with EVP or without. A security camera with a videocassette recorder was positioned above the PACS workstation. Four radiologists reviewed the images during their normal work schedule. The current diagnostic image was used to determine if the case contained EVP or non-EVP images. The videotapes of the sessions were reviewed to determine diagnostic viewing times and how zoom and/or window and level manipulation was used. RESULTS: Viewing time was significantly longer for the non-EVP than the EVP cases. The difference occurred with all readers. Window and level manipulation was used on 35% of the EVP and 41% of the non-EVP images. Zoom was used on 64% of the EVP and 69% of the non-EVP images. Average time spent using zoom and window and level manipulation was significantly shorter with the EVP than with the non-EVP images. CONCLUSION: EVP of chest images displayed on PACS monitors significantly improved workflow as measured by viewing time. EVP decreased use of window and level manipulation and zooming and the amount of time each one was used.

Evaluation of a flat CRT monitor for use in radiology.

Medical radiographs based on familiar projection techniques are planar images traditionally displayed by placing on a flat surface viewbox. Presenting these planar images in digital form on a traditional monitor with a curved surface may cause distortions, possibly affecting diagnoses. This would be true especially if physical linear dimensions of the anatomy are important. Reflections from ambient lights behind the observer also could be a problem with curved displays. The goal of this study was to compare physical and psychophysical performance of a flat-surface display monitor with a traditional curved-surface monitor. Two display monitors with different types of front glass-panel surfaces were evaluated. The first monitor had a traditional curved surface, and the other had a flat surface. Physical measurements included dynamic range, display function, veiling glare, and spatial uniformity. An observer performance study used low-contrast, square-wave patterns to determine just-noticeable differences. Ambient lights were turned off in one condition and on in the other. Physical measurements showed that the display functions were nearly identical, but uniformity, veiling glare, and signal-to-noise-ratio were better for the curved monitor. Observer performance was better overall with the curved monitor, but the degradation in performance between lights off and lights on was greater for the curved than flat monitor. The greater degradation with the lights on could be attributed to more reflections off the curved than the flat monitor. A flat-surface display monitor may be useful for viewing clinical radiographs.

Usefulness of segmented trueFISP cardiac pulse sequence in evaluation of congenital and acquired adult cardiac abnormalities.

OBJECTIVE: The purpose of this study is to compare ultrashort TR, segmented trueFISP (fast imaging with steady-state precession) cine MR imaging with segmented FLASH (fast low-angle shot) cine MR imaging for the detection and characterization of congenital and acquired adult cardiac abnormalities. SUBJECTS AND METHODS: Twenty-five patients with known or clinically suspected cardiac abnormalities were imaged on a 1.5-T scanner. Valve plane movies were obtained in patients with suspected valve morphology or function abnormalities or whose horizontal long-axis images showed jets. For each patient, three radiologists independently compared corresponding matched cine FLASH and trueFISP movies for image quality in evaluating anatomy and function of the great vessels and heart. Image quality was rated on a five-point scale, and data were analyzed using both a Wilcoxon's signed rank test and a repeated-measures analysis of variance. RESULTS: Image quality ratings of trueFISP and FLASH showed a statistically significant difference (F = 58.67; df = 1, 72; p < 0.0001), with the average rating for the trueFISP images being significantly higher (mean rating, 4.1 +/- 0.92) than that for the FLASH images (mean, 3.0 +/- 1.0). However, valve architecture in the aortic valves appeared to be better visualized and was more easily measured in valve plane images with FLASH. No statistically significant differences among the ratings of the interpreters (F = 0.018; df = 2, 72; p = 0.9821) were evident, and, therefore, no suggestion of bias was indicated (F = 0.775; df = 1, 2; p = 0.4645). TrueFISP yielded the correct diagnosis prospectively in 13 (100%) of 13 patients, whereas FLASH yielded the correct diagnosis in 12 (92%) of 13 patients. CONCLUSION: TrueFISP images depict morphologic and functional abnormalities with greater clarity and provide greater diagnostic confidence than FLASH images-and in a fraction of the time. A specific exception is in the assessment of valve leaflet architecture and cross-sectional area calculation (i.e., bicuspid aortic valves); in these evaluations, FLASH maintains a complementary diagnostic imaging role.

Fluctuations in service loads in an established telemedicine program.

The goal of this investigation was to determine if there were identifiable patterns in the volume and types of teleconsults provided by an established telemedicine program over an extended period of time. Data from over 3 years of providing telemedicine consults within a university-based telemedicine programs were analyzed to identify trends and points of significant change in service provision. Teleconsult volume over a 40-month period was best fit by a logarithmic transformation of the regression curve that is characteristic of slow but steady growth. Consults have been provided in 53 subspecialties, with an average of 12 different subspecialties each month. Number of subspecialties per month was best fit by a sixth-order polynomial. Teleconsult volume has varied on a monthly basis, but overall volume has increased over time. This program has maintained its initial goal of being a multispecialty provider. Analyzing telemedicine consult data over extended periods of time is especially useful for long-term program evaluation and development of a successful business plan.

Gaze dwell times on acute trauma injuries missed because of satisfaction of search.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether satisfaction of search (SOS) errors in patients with multiple traumas are caused by faulty visual scanning, faulty recognition, or faulty decision making. MATERIALS AND METHODS: A series of radiographs were obtained in patients with multiple traumas. Radiologists interpreted each series under two experimental conditions: when the first radiograph in the series included a fracture, and when it did not. In the first experiment, the initial radiographs showed nondisplaced fractures of the extremities (minor fractures); in the second experiment, the initial radiographs showed abnormalities of greater clinical importance (major fractures). Each series also included a radiograph with a subtle (test) fracture and a normal radiograph on which detection accuracy was measured. In each experiment, gaze dwell time was recorded as 10 radiologists reviewed images from 10 simulated cases of multiple trauma. RESULTS: An SOS effect could be demonstrated only in the second experiment. Analysis of dwell times showed that search on subsequent radiographs was shortened when the initial radiograph contained a fracture; however, the errors were not based on faulty scanning. CONCLUSION: The SOS effect in musculoskeletal trauma is not caused by faulty scanning. Demonstration of an SOS effect on test fractures with major but not minor additional fractures suggests that detection of other fractures is inversely related to the severity of the detected fracture.

The solitary pulmonary nodule on chest radiography: can we really tell if the nodule is calcified?

OBJECTIVE: This study was designed to assess the ability of radiologists to accurately detect calcification within a solitary pulmonary nodule with chest radiography. MATERIALS AND METHODS: Thirty-five solitary pulmonary nodules that were examined by both posteroanterior and lateral chest radiography and on thin-section CT were retrospectively identified. Fourteen radiologists blinded to the results of CT assessed the nodules for the presence or absence of calcification using chest radiographs alone. The radiologists then assigned one of six values on the basis of their confidence in that assessment. The accuracy and confidence values for each nodule were analyzed on the basis of the presence or absence of calcification as seen on CT. Receiver operating characteristic (ROC) curves were generated. RESULTS: The positive predictive value of a "definitely calcified" assessment was 0.93. Combining all levels of radiologists' confidence, the sensitivity of the chest radiograph in the detection of calcium was 0.50 and the specificity was 0.87. There was no difference in the confidence levels reported between the calcified and noncalcified nodules, and there was no correlation of nodule size with accuracy or confidence level. CONCLUSION: The ability of radiologists to detect calcium in a solitary pulmonary nodule by chest radiography was low, as defined by the ROC data. Of the "definitely calcified" nodules, up to 7% may not be calcified and may be potentially malignant. Without documentation of long-term stability, a low threshold for recommending CT may be appropriate.

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.

Role of faulty decision making in the satisfaction of search effect in chest radiography.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether defective pattern recognition or defective decision making is more to blame for satisfaction of search (SOS) errors in chest radiography. MATERIALS AND METHODS: Fifty-eight chest radiographs-half of which demonstrated diverse, native abnormalities-were read by 20 observers. The radiographs were read twice, once with and once without the addition of a simulated pulmonary nodule. Observers provided a verbal account of their focus of attention, indicating suspicious features and regions considered during their inspection of the radiograph. Observers also provided a separate account of the abnormalities they would include in a radiologic report. RESULTS: When the authors considered only those reports that did not refer to the simulated nodules, they found no reduction in the area under the proper receiver operating characteristic (ROC) curves in cases that contained nodules. A smaller SOS effect, however, was demonstrated with analysis of events in which the native abnormality was missed in one condition but not the other. Verbal protocols suggested that the SOS errors were mainly caused by recognition failure rather than faulty decision making. CONCLUSION: Describing their focus of attention may have prompted observers to inspect the radiographs in a more deliberate, systematic way, thus reducing the SOS effect. More residual SOS errors were caused by defective pattern recognition than by faulty decision making.

Emergency department coverage by academic departments of radiology.

RATIONALE AND OBJECTIVES: The purpose of this study was to survey academic radiology departments to determine how emergency radiology coverage is handled and whether there are any prerequisites for those individuals providing this coverage. MATERIALS AND METHODS: The authors developed a simple two-page survey and sent it to a total of 608 program directors, chiefs of diagnostic radiology, chairpersons, and chief residents at academic departments of radiology. RESULTS: Of the 608 surveys sent, 278 (46%) were returned. More than half of the departments have an emergency radiology section that provides "wet read" coverage during the day, and most academic departments cover the emergency department during the night and on weekends. Nighttime and weekend coverage is handled mostly by residents. Most departments give time off for lunch, with few other prerequisites for faculty who provide emergency coverage. Sixty percent of the departments have teleradiology capability, and many use it for emergency department coverage. CONCLUSION: These results can serve as the basis for discussion and comparison with other institutions regarding a variety of aspects of emergency department coverage.

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.

The importance of perception research in medical imaging.

The goal of this paper is to provide the reader with an introduction to the importance of perception research in medical imaging. It is well known that radiologists' performance is not perfect: they make both false positive and false negative decisions, both of which can impact on patient care and treatment. Some of these errors can be attributed to technical difficulties such as underexposing a plain film X-ray image. Such technical explanations cannot, however, account for all the errors that are made; missed lesions are often found in retrospect. These errors can be attributed to perceptual and/or cognitive factors. The study of why these perceptual and cognitive errors occur and what steps can be taken to ameliorate them is a relatively small but growing area in the field of medical imaging. Understanding the capabilities of the human visual system with respect to medical imaging is becoming even more important as we make the transition from the traditional film-based display to soft-copy monitor viewing of medical images. If we understand what the human visual system is capable of, we can tailor the display of medical information to take advantage of these perceptual capacities.

Patterns of use and satisfaction with a university-based teleradiology system.

The Radiology Department at the University of Arizona has been operating a teleradiology program for almost 2 years. The goal of this project was to characterize the types of cases reviewed, to assess radiologists' satisfaction with the program, and to examine case turnaround times. On average, about 50 teleradiology cases are interpreted each month. Computed tomography (CT) cases are the most common type of case, constituting 65% of the total case volume. Average turnaround time (to generate a "wet read" once a case is received) is about 1.3 hours. Image quality was rated as generally good to excellent, and the user interface as generally good. Radiologists' confidence in their diagnostic decisions is about the same as reading films in the clinical environment. The most common reason for not being able to read teleradiology images is poor image quality, followed by lack of clinical history and not enough images.

Evaluation of an experimental low-attenuation gastrointestinal contrast agent for CT imaging of intestinal ischemia in an animal model.

RATIONALE AND OBJECTIVES: The authors evaluated the use of MRX-320, a low-attenuation, expansile oral contrast agent, for the demonstration of intestinal ischemia in an animal model. MATERIALS AND METHODS: Nine dogs were given either MRX-320, water, or diatrizoate as an oral contrast agent through a jejunostomy tube. Two dogs received no oral contrast agent. Helical computed tomography (CT) was performed before the intravenous injection of 2.5 mL/kg iohexol at 4 mL/sec, during the arterial phase, and during the portal venous phase. Mesenteric ischemia was surgically induced, and the imaging protocol was repeated. Three readers rated the randomly assigned images for quality and demonstration of ischemia. Attenuation values for the intestinal lumen and wall were recorded. RESULTS: Examinations performed with MRX-320 provided the best discrimination between ischemic and nonischemic conditions (P < .05), followed by examinations with no oral contrast medium, examinations with water, and examinations with diatrizoate. Images obtained with MRX-320 also scored significantly higher on measures of image quality than those obtained with water or no oral contrast medium (P < .05). On images obtained with MRX-320, the bowel lumen measured -836.5 HU (P < .05 compared with other techniques). Water provided the least uniformity of distention, and diatrizoate provided the least mucosal detail. CONCLUSION: The use of MRX-320 as an oral contrast agent with an intravenous bolus of iohexol at CT increased reader confidence for the diagnosis of intestinal ischemia and improved subjective measures of image quality.