Biomedical subjects
Publications and source records attributed to A D Vellet.
Real-time sonography of the eye is a technique that is rapidly performed and readily available in most sonography departments. It is less expensive than CT and MR imaging and, if necessary, may be performed at the patient's bedside. This essay demonstrates a few of the large number of clinical entities that may be successfully examined with this technique.
Hepatic neoplasia can be accurately characterized with magnetic resonance imaging of architectural, signal and dynamic gradient-echo contrast-enhancing features. Architectural characteristics valuable in determining the nature of hepatic neoplasia include the outer and inner contours of the lesion; the presence of fibrous encapsulation; the presence, signal and enhancing characteristics of a central scar; the presence and distribution of hemorrhage or necrosis; the relation of the lesion to regional vasculature and bile ducts; and lesion multiplicity. The signal characteristics in spin-echo and gradient-echo pulse sequences of the adjacent hepatic parenchyma and the lesion itself provide further information. In certain instances hepatic neoplasia can be definitively characterized on dynamic gradient-echo pulse sequences obtained after administration of the contrast agent gadolinium.
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Although magnetic resonance imaging (MRI) has become the imaging technique of choice in Canada and elsewhere in the evaluation of knee disorders, magnetic resonance units are frequently unavailable, or access to them is greatly restricted. The authors have found that computed tomography (CT) can sometimes be successfully substituted for MRI as a noninvasive method for imaging a wide variety of knee disorders. This article reviews the CT appearance of normal knee anatomy and illustrates a wide variety of pathological conditions that can be successfully evaluated.
Through its ability to evaluate the individual components of the rotator cuff, the labral-capsular complex, the subacromial and subdeltoid spaces, and the glenoid, humerus, clavicle, and acromion, MRI provides a means of comprehensively evaluating the shoulder. Further advances in the use of intra-articular MRI contrast agents will undoubtedly enhance the role of MRI in the evaluation of subtle labralcapsular pathology. Although they are experimental, kinematic studies of the shoulder may provide valuable insight into the pathogenesis of disorders such as impingement syndrome. The ability of MRI to provide detailed pathologic information about individual components of the shoulder, particularly the rotator cuff, presents a challenge to shoulder surgeons. Patient symptomatology should be correlated with MRI findings and the clinical significance attached to different pathologies reevaluated. Through rigorous confirmation of MRI findings, dedicated therapeutic algorithms can be established based on detailed clinicopathologic data. Present and future surgical and nonsurgical management of the shoulder will undoubtedly be shaped by MRI.
In the past, magnetic resonance imaging (MRI) of the pancreas has suffered from many technical obstacles that have precluded success, particularly in the evaluation of adenocarcinoma. However, with the improved quality of pancreatic MRI and the use of intravenous gadolinium as a contrast agent, MRI is now proving useful in the evaluation of pancreatic adenocarcinoma. MRI's main role is in accurate preoperative staging when computed tomography and ultrasonography provide equivocal results.
A controlled, prospective study of 30 patients with suspected acute internal derangement of the knee was undertaken to evaluate the sensitivity, specificity, predictive value, and accuracy of nonorthogonal (oblique) sagittal magnetic resonance imaging (MRI) in the assessment of anterior cruciate ligament (ACL) injuries. Thirty patients with acute hemarthroses underwent MRI within 12 days of injury, followed by arthroscopy within 24 h of the MRI. A control population of 30 chondromalacia patients underwent similar evaluation. In the acute hemarthrosis patient population, the incidence at arthroscopy of acute complete ACL tears was 60% (18/30); of partial ACL tears, 13.3% (4/30); and of chronic tears, 10% (3/30). A normal ACL was found in 16.6% (5/30) of patients. In the MRI evaluation of patients with suspected ACL injury the following results were obtained for both acute and chronic complete disruption on orthogonal (sagittal) and nonorthogonal (oblique sagittal) imaging, respectively: sensitivity, 61 (16/26) versus 100%; specificity, 70 (21/34) versus 100%; positive predictive value, 61 (16/26) versus 100%; negative predictive value 70 (24/34) versus 100%; and accuracy, 66 (40/60) versus 100%. In the evaluation of partial ACL injury, four partial tears were correctly diagnosed on nonorthogonal MRI, with one false-positive diagnosis. Orthogonal imaging failed to correctly identify any of the partial ACL injuries. Two patients in the control population demonstrated evidence of chronic ACL tears. We believe that we have demonstrated the superiority of T2-weighted nonorthogonal sagittal over conventional orthogonal sagittal ACL MRI in the evaluation of ACL injury.
A case of a large exophytic renal angiomyolipoma is presented. Despite the features on excretory urography suggestive of an extrarenal mass, computed tomography provided information concerning the origin and pathological nature of the lesion.
Eye metastases in carcinoma of the cervix are very rare, although not an uncommon presentation of carcinomas in general. A patient with eye symptoms secondary to retro-ocular metastatic carcinoma of the cervix is presented.
Fibromyalgia is a syndrome manifested by chronic, diffuse musculoskeletal aching and soreness, palpable muscle tender points, and other symptoms. Standardized clinical diagnostic criteria have recently been developed. Skeletal muscle has been postulated as the end organ in this disease. Biochemical, histologic, electromyographic, and conventional radiographic studies have demonstrated no definitive abnormality. This study sought to establish whether magnetic resonance (MR) imaging could demonstrate any abnormality in these patients. Eighteen patients were entered in the study, 14 of whom were able to complete their examinations. T1-weighted, T2-weighted, gradient-echo, and STIR (short-tau inversion-recovery) sequences were performed in all patients, with selected patients examined with T1-weighted, gadopentetate dimeglumine-enhanced sequences. The trapezius and suboccipital regions were imaged in patients who, clinically, had active fibromyalgia. No abnormalities could be detected. The authors conclude that the conventional MR imaging used in this study was unable to depict any primary skeletal muscle abnormality in fibromyalgia.
Thirty shoulders in 20 volunteers (average age, 29 years; range, 17 to 49) with no shoulder symptoms or known abnormalities were scanned using magnetic resonance imaging. All scans were interpreted by one radiologist who was blinded to clinical data. Appearance of rotator cuff tendons on the images was graded. Grade 0 was normal, homogeneous low signal intensity structure. Grade 1 lesion was focal, linear, or diffuse intermediate signal through the tendon. Grade 2 lesion was high signal intensity within the tendon and less than full thickness. Grade 3 was high signal intensity through full thickness of the tendon. No supraspinatus or infraspinatus tendons were grade 0 (normal); all supraspinatus and infraspinatus tendons had grade 1 changes through the tendons; and 7 of 30 (23%) of the tendons had grade 2 changes. None of the 30 shoulders had grade 3 changes in the rotator cuff tendons. There is a wide array of abnormal magnetic resonance imaging signals in shoulders of young asymptomatic individuals, but they do not have full-thickness rotator cuff tears (grade 3 lesion). Nonenhanced magnetic resonance imaging may be of limited value in defining rotator cuff injury in a patient with shoulder pain unless a full-thickness rotator cuff tear is suspected clinically.