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Biomedical subjects

F L Thaete

Publications and source records attributed to F L Thaete.

29 records · Page 2Linked to original sources
PubMed1994

Sequential viewing of abdominal CT images at varying rates.

PURPOSE: To evaluate radiologists' ability to detect abdominal masses during sequential viewing of series of computed tomographic (CT) scans at varying rates. MATERIALS AND METHODS: Receiver operating characteristic (ROC) analysis was used to assess the ability of five experienced radiologists to determine the presence or absence of subtle abdominal masses in 29 cases (15 positive, 14 negative) while viewing CT scans sequentially at different rates (0.5, 1, 2, 4, 7, and 21 images per second) and also at reader-selectable rates. RESULTS: Even at extremely fast viewing rates (21 images per second), radiologists performed significantly better (P < .05) than would be expected by chance alone (average area Az under the ROC curve = 0.73 vs 0.5). As the viewing rate decreased, their performance increased. The reader-selectable mode was better than any fixed-rate cine mode (average Az = 0.93). CONCLUSION: Fixed-rate sequential viewing of CT images for the primary diagnosis of subtle abdominal masses should be restricted to no more than one or two images per second, but the reader-selectable viewing mode is preferable to any fixed-rate cine mode.

Humans↗
PubMed1994

Digital radiography and conventional imaging of the chest: a comparison of observer performance.

OBJECTIVE: The purpose of this study was to compare observer performance in interpreting high-quality, digitally acquired computed radiographs of the chest displayed on either laser-printed radiographs or a workstation with observer performance in interpreting conventional chest radiographs. SUBJECTS AND METHODS: We performed a receiver-operating-characteristic study in which the presence or absence of five abnormalities was determined by nine experienced radiologists on 310 posteroanterior radiographs of the chest displayed in three forms: conventional radiographs, laser-printed films of digital radiographs, and digital radiographs on a high-resolution workstation. RESULTS: The results of our study suggest that observer performance with laser-printed films of digital radiographs obtained with high-resolution (4K x 5K), high-contrast sensitivity (12 bits) and appropriate exposure is comparable to observer performance with conventional radiographs. Observer performance with digital radiographs displayed on the workstation was found to be significantly lower for abnormalities that contained high-frequency and low-contrast information (e.g., interstitial disease and pneumothorax). CONCLUSION: Computed radiography technology can produce image quality that is adequate for interpreting posteroanterior radiographs of the chest. Observer performance is not as good when radiographs displayed on workstations are used to diagnose specific abnormalities.

Humans↗
PubMed1993

Requirements for PACS: users' perspective.

The applications for which picture archiving and communication systems (PACS) will be used must dictate the technological requirements. Technology-driven integrated PACS have been implemented and tested in a variety of clinical environments. PACS do not generate new revenues, albeit they may affect the bottom line of health care delivery systems through increased efficiency of radiology and, perhaps more important, of the other physicians who use radiologic services. User performance expectations require that trade-offs are evaluated and compromises are made when PACS are designed using currently available technology. In this report, functional requirements for clinical PACS are discussed. These include reliability, speed, ease of use, connectivity, and upgradability. The advantages and disadvantages of specific choices are presented from a utility perspective of an end user.

Computer Communication Networks↗
PubMed1993

Blood flow in the portal vein: velocity quantitation with phase-contrast MR angiography.

Quantitative phase-contrast magnetic resonance (MR) angiography of the portal vein was prospectively evaluated in 79 fasting patients and 23 healthy volunteers. Images were obtained during a 12-second breath-hold acquisition in the coronal (n = 102) and axial (n = 11) planes. Pathologic correlation was available in 55 of 79 patients and included findings of cholangiocarcinoma, cirrhosis, hepatocellular carcinoma, hepatitis, and metastatic disease. Forty-one patients had correlative Doppler ultrasound (US) findings. MR and US findings correlated as to flow direction in all cases. In nine patients, Doppler US velocity measurements were available and closely correlated with MR findings. A comparison of axial and coronal portal venous phase-contrast measurements in 11 patients revealed no substantial difference with regard to the plane used. Quantitative phase-contrast MR angiography is a simple and rapid technique for the assessment of portal venous patency, flow direction, and flow velocity and, combined with high-resolution conventional MR imaging, may obviate the current use of both computed tomographic and US examinations.

Blood Flow Velocity↗
PubMed1993

Contrast examination of the small bowel in patients with small-bowel transplants: findings in 16 patients.

OBJECTIVE: The purpose of this study was to describe the findings on contrast examinations of the gastrointestinal tract in patients with small-intestinal transplants. SUBJECTS AND METHODS: Sixteen consecutive adult transplant recipients received a total of 17 allografts: eight isolated small-bowel, six small-bowel and liver, and three multivisceral (stomach, duodenum, pancreas, small-bowel, liver). Grafts included the entire mesenteric small bowel. Gastrointestinal contrast studies were done in asymptomatic patients according to protocol and in patients having clinical indications for examination. Median time from transplantation to examination was 78 days (range, 5-768 days). Seventy-five gastrointestinal contrast examinations were performed: 53 upper gastrointestinal and small-intestinal series, 12 upper gastrointestinal series, eight enteroclyses, and two water-soluble contrast enemas. Radiographs were analyzed for postsurgical anatomy, integrity of anastomoses, allograft radiologic appearance, small-bowel transit time, and rate of gastric emptying. RESULTS: Usual postsurgical anatomy included native-to-donor duodenojejunal, jejunojejunal, and gastrogastric anastomoses and donor-to-native ileocolonic and ileoileal anastomoses. No anastomotic complications were found. Leaks at native duodenal and colonic stumps resulted in a duodenocutaneous fistula and an abscess, respectively. Moderate to marked thickening of mucosal folds consistent with edema was present in nine allografts (53%) and 11 (17%) of 66 upper gastrointestinal and small-intestinal examinations, primarily in the early postoperative period. Chronic loss of allograft mucosal folds developed in four grafts in three patients; pathologic diagnoses included acute and chronic rejection and enteric infection; a jejunocutaneous fistula developed in one such patient. Transit times of barium through the small intestine ranged from 0.2 to 17.8 hr (median, 2 hr). Self-limited delayed gastric emptying was present in 14 patients (88%) and 32 (60%) of 54 upper gastrointestinal and small-intestinal examinations. CONCLUSION: Gastrointestinal contrast examinations in recipients of small-bowel transplants are useful for assessing graft anatomy, enteric anastomoses, and gastrointestinal motor function. Most intestinal grafts showed normal caliber and mucosal pattern and exhibited active peristalsis. Abnormal findings included self-limited postoperative edema of graft mucosal folds, chronic loss of the mucosal folds due to rejection and/or enteric infection, delayed gastric emptying that improved with time, leaks from native duodenal and colon stumps, and a jejunocutaneous fistula in a failing graft. Small-intestinal transit times were similar to those observed in patients not receiving transplants, although there was wide variation.

Adult↗
PubMed1992

MR knee imaging: axial 3DFT GRASS pulse sequence versus spin-echo imaging for detecting meniscal tears.

The knees of 17 patients (34 menisci) referred for magnetic resonance (MR) imaging to evaluate knee pain were examined using thin axial three-dimensional Fourier transform (3DFT) gradient-refocused acquisition in a steady state (GRASS) images through the menisci, to determine if this method is sensitive and specific for detecting meniscal tears. Results were compared with spin-echo images with long TR and double-echo TE in both coronal and sagittal planes. Arthroscopy results, available in each case, were used as the "gold standard." Twelve meniscal tears were identified at arthroscopy. Axial 3DFT GRASS technique detected 10 of the 12 meniscal tears compared to 9 or 12 using spin-echo technique. With axial 3DFT GRASS technique one false-positive meniscal tear was reported, compared with two false-positive tears on spin-echo images. Axial 3DFT GRASS images were very useful in detecting peripheral tears, showing displaced meniscal fragments, and evaluating complex tears. In this small study, thin axial 3DFT GRASS images were comparable to spin-echo images for detecting meniscal tears, and were helpful in complicated cases in which they provided complementary information to that obtained from spin-echo images.

Adolescent↗
PubMed1991

Primary CT diagnosis of abdominal masses in a PACS environment.

Whether the display medium--film versus cathode ray tube (CRT)--affects observer performance during interpretation of computed tomographic (CT) images is an important research issue in these times of implementation and growth of picture archiving and communications systems in radiology. The authors performed a multiobserver receiver operating characteristic (ROC) study to determine the performance of radiologists who read abdominal CT studies displayed on film, as well as on a high-resolution workstation (video monitor) that made use of three different display modes. A total of 166 examinations were evaluated by eight radiologists, who recorded their ordinal confidence ratings of the demonstration of presence or absence of abdominal masses. ROC analysis showed small differences in the confidence ratings assigned by individual readers for the detection and interpretation tasks. Results for the group as a whole showed no significant reduction or improvement in observer performance when ratings for any one of the workstation display modes were analyzed. The results of this study demonstrate that current CRT display technology is adequate for enabling the primary detection of abdominal masses with CT examinations.

Abdominal Neoplasms↗
PubMed1990

Practical issues of experimental ROC analysis. Selection of controls.

Receiver operating characteristics (ROC) analysis has been used in many medical imaging applications during the past decade. With the recent expansion of the ROC methodology to multi-disease studies, several reports have begun to address both the theoretical and experimental design issues associated with such studies. While the appropriate selection, classification, and verification of actually positive cases is carefully addressed in the literature, similar considerations are rarely given to the selection of actually negative controls for these studies. In this paper, theoretical considerations and experimental data are provided to demonstrate the significance of this very issue.

Case-Control Studies↗
PubMedDate not supplied

Tibial meniscal dynamics using three-dimensional reconstruction of magnetic resonance images.

The human knee joint represents a complex biomechanical system of which the menisci are an integral component. At present, little data exists describing the meniscal kinematics of the intact knee. Accordingly, a three-dimensional reconstruction magnetic resonance image model was used to explore this issue. Five fresh cadaveric knees were examined by magnetic resonance imaging throughout a full range of motion at 10 degrees intervals. Computer three-dimensional images of the menisci were generated and evaluated for anteroposterior excursion and deformation. During flexion, the posterior excursion of the medial meniscus was 5.1 mm, while that of the lateral meniscus was 11.2 mm. The anterior horn segments were shown to be more mobile than the posterior horn segments bilaterally. Prior limitations of meniscal kinematic assessment may be overcome with advanced imaging techniques such as magnetic resonance imaging and three-dimensional reconstruction. The menisci are highly mobile and easily deformed structures within the intact, cadaveric knee. This imaging technique may prove useful in the elucidation of meniscal dynamics. In the future, similar techniques may be applied clinically to aid in the diagnosis of joint dysfunction.

Biomechanical Phenomena↗
PubMedDate not supplied

Rupture of the pectoralis major muscle in a collegiate football player. Use of magnetic resonance imaging in early diagnosis.

We have reported an unusual case of pectoralis major muscle rupture and repair. There were three interesting aspects of this case. First, the injury occurred in a football player with an unusual mechanism of injury. Second, MRI using special techniques was valuable in confirming the diagnosis acutely and in planning treatment. Finally, we reported on the use of suture anchors to secure the avulsed tendon. We recommend the early use of MRI for diagnosis and in planning treatment of suspected pectoralis major muscle ruptures.

Adult↗