Biomedical subjects
A D Vellet
Publications and source records attributed to A D Vellet.
Gadolinium-enhanced dynamic MRI of the fractured carpal scaphoid: preliminary results.
The aim of the present report was to evaluate the vascularity of fracture fragments of the fractured carpal scaphoid in the acute (< 4 weeks) and chronic (> 3 months) phases using a gadolinium-enhanced dynamic MRI sequence. Eight patients with acute scaphoid fractures, six patients with chronic scaphoid fractures, and three control patients without fractures were evaluated using a T1-weighted fast spoiled gradient recalled acquisition (fSPGR) sequence with gadolinium-DTPA enhancement (0.1 mmol/kg bodyweight). Signal intensity over time plots were obtained using region of interest measurements from both fracture fragments. Enhancement factors (EF) were then calculated from the plots. No enhancement of the scaphoid was seen in control subjects (EF: distal scaphoid pole 1.04 +/- 0.01, proximal pole 1.07 +/- 0.08). In acute fracture patients, enhancement of the distal pole was greater than that of the proximal in all cases but one in which the two poles enhanced in a similar fashion (EF: distal 1.99 +/- 0.77, proximal 1.43 +/- 0.99). In chronic fracture patients the enhancement pattern was reversed, as the proximal pole enhanced to a greater degree than the distal with the exception of one case where both poles enhanced equally (EF: distal 1.74 +/- 0.52, proximal 2.64 +/- 0.50). Using a two-tailed non-parametric Mann-Whitney U-test, the difference in enhancement of the proximal poles between the acute and chronic groups was found to be highly significant (P < 0.003). Dynamic contrast-enhanced (fSPGR) MRI demonstrates significant differences in the enhancement patterns of the scaphoid when chronic and acute fractures are compared.
Diagnostic equivalence of conventional and fast spin echo magnetic resonance imaging of the anterior cruciate ligament of the knee.
Many techniques and pulse sequences have been devised for the assessment of the anterior cruclate ligament. The present study compares fast spin echo (FSE) imaging to conventional spin echo imaging at a field strength of 1.5 T in an effort to determine if these sequences are diagnostically equivalent. Where available, arthroscopy was also done. A total of 52 patients were imaged using both FSE and conventional spin echo sequences. Eight volunteers were used as controls. Arthroscopy was performed on 10 patients. The anterior cruciate ligament was assessed in a blinded fashion by three radiologists. The Kappa statistic was then used to determine the percentage agreement between FSE and conventional spin echo imaging. Fast spin echo sequencing demonstrated a sensitivity of 100%, a specificity of 94.8% and an accuracy of 96.3% when compared to arthroscopy. Conventional spin echo imaging and arthroscopy had a sensitivity of 100%, specificity of 84.6% and an accuracy of 88.9%. The remaining 34 patients who did not undergo arthroscopy were followed clinically because clinical and imaging findings were not suggestive of ACL tears. These demonstrated 72% agreement between FSE and conventional spin echo imaging using the Kappa statistic, with regards to calling ACL normal or having only a low-grade partial tear. Fast spin echo imaging produces images of the anterior cruciate ligament that have similar diagnostic accuracy to conventional spin echo images (P < 0.05) within a much shorter scan time. These results however, require further validation in a larger group, preferably with arthroscopic correlation.
Prostatic cryosurgery: use of MR imaging in evaluation of success and technical modifications.
PURPOSE: To evaluate the usefulness of contrast material-enhanced magnetic resonance (MR) imaging in objective assessment of prostatic cryosurgery and the role of MR imaging in the modification of prostatic cryosurgical technique. MATERIALS AND METHODS: Thirty-eight consecutive patients with localized (T1-3, N0, M0) prostatic adenocarcinoma treated with prostatic cryosurgery underwent MR imaging without contrast enhancement before cryosurgery and unenhanced and gadolinium-enhanced MR imaging within 1-3 weeks after cryosurgery. The first 20 patients also underwent MR imaging at 3 months after cryosurgery. MR imaging findings were correlated with those from transrectal ultrasound-directed prostatic staging biopsy. RESULTS: Cryonecrotic prostate was identified as avascular regions characterized by absolute signal void on contrast-enhanced images. With progressive modification of cryosurgical technique, complete cryoablation of the prostate was achieved in the latter nine of the 38 patients. When cryoablation was considered complete according to MR imaging criteria, findings invariably correlated with those at biopsy, with no residual prostate tissue or tumor. CONCLUSION: Gadolinium-enhanced MR imaging of the prostate after cryosurgery provides a highly accurate means of monitoring success. Objective MR imaging findings allow modifications to the technology and technique, resulting in optimal therapeutic results with prostatic cryosurgery.
Intraosseous lipoma of the distal femur: MRI appearance.
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The frequency of venous thrombosis in cemented and non-cemented hip arthroplasty.
We randomised 250 patients undergoing unilateral, elective hip arthroplasty for osteoarthritis to receive either a cemented or a non-cemented Mallory Head prosthesis. Aspirin was used as prophylaxis against thromboembolism during the first half of the study and adjusted-dose warfarin during the second half. Postoperatively, all patients were asked to have bilateral venography and 80% agreed. All were evaluated clinically for pulmonary embolism. There was no difference in the frequency of deep-venous thrombosis between the two groups (50% cemented nu 47% non-cemented, p = 0.73; 95% CI of the difference -13.6% to 19.3%). Three of the 64 patients (5%) in whom venography had demonstrated isolated distal thrombi developed pulmonary emboli.
MR imaging field strength: prospective evaluation of the diagnostic accuracy of MR for diagnosis of multiple sclerosis at 0.5 and 1.5 T.
PURPOSE: To compare the diagnostic efficacy of middle-field-strength and high-field-strength magnetic resonance (MR) imaging in diagnosis of multiple sclerosis. MATERIALS AND METHODS: One hundred thirty-two patients with suspected multiple sclerosis underwent MR imaging at 0.5 and 1.5 T. Imaging parameters were identical except for band width optimization at middle field strength. Images were interpreted by radiologists expert in MR imaging who were blinded to diagnosis and field strength. The diagnosis of multiple sclerosis was made by experienced neurologists, and indeterminate cases and patients without clinical evidence of multiple sclerosis were followed up for 6 months to 1 year. RESULTS: There was no difference in accuracy, sensitivity, or specificity between scanners in the diagnosis of multiple sclerosis or white matter disease. Equal numbers of lesions were detected at both field strengths in all parts of the brain. Image quality was always good or adequate at middle field strength. CONCLUSION: Higher field strength does not confer higher accuracy in the diagnosis of multiple sclerosis with current-generation MR imagers.
Anterior cruciate ligament tear: prospective evaluation of diagnostic accuracy of middle- and high-field-strength MR imaging at 1.5 and 0.5 T.
PURPOSE: To compare the diagnostic efficacy of current-generation middle- and high-field-strength magnetic resonance (MR) imagers in the diagnosis of anterior cruciate ligament (ACL) tears. MATERIALS AND METHODS: In 114 of 230 patients referred for knee imaging, MR imaging at 0.5 and 1.5 T was performed with identical sequences but with a slightly longer total imaging time and bandwidth optimization at 0.5 T. Radiologists were blinded to diagnosis and field strength. Sensitivity, specificity, and accuracy were determined, and ACL tear was confirmed by means of arthroscopy and pathology. RESULTS: There was no difference between the field strengths in accuracy, sensitivity, or specificity for the diagnosis of ACL tears in 86 patients with disrupted ACLs and 28 patients with intact ACLs. Accuracy for all ACL tears was 90% at 0.5 T and 91% at 1.5 T. Similarly, there were no differences in diagnosis of meniscal tears (79 with, 149 without) or posterior cruciate ligament tears (seven with, 107 without). CONCLUSION: Higher field strength does not confer higher accuracy in the diagnosis of ACL tears at MR imaging.
Patellar tendinitis: MR imaging features, with suggested pathogenesis and proposed classification.
PURPOSE: To characterize the magnetic resonance (MR) imaging features of patellar tendinitis. MATERIALS AND METHODS: Fifteen patients with a clinical diagnosis of patellar tendinitis underwent gadolinium-enhanced MR imaging of the knee. RESULTS: Grades of patellar abnormality, based on findings in the enthesial region at MR imaging, correlated with signs of increasing fibrovascular repair: grade 1 (n = 4), enhancing area adjacent to patellar apex, with marginal zone of intermediate signal intensity, and a patellar apical chondral-bone avulsion; grade 2 (n = 5), same signs as grade 1 damage but without avulsion; grade 3 (n = 6), homogeneous, nonenhancing area of intermediate signal intensity adjacent to the patellar apex seen on all images. Changes were most obvious posteriorly and involved the central and medial thirds of the tendon. Chronic injury to the medial retinaculum was a common associated finding. CONCLUSION: Patellar tendinitis demonstrates a consistent spectrum of changes at MR imaging that can aid understanding of the origin and treatment of damage.
Self-contained, inflatable penile prosthesis: magnetic resonance appearance.
The appearance of an inflatable penile prosthesis, visualized on a short tau inversion recovery sequence, is reported, in a patient who had magnetic resonance imaging for pelvic pain subsequent to radical cystoprostatectomy for bladder carcinoma. With suppression of adjacent fat signal, the prosthesis is well delineated from adjacent structures. The fluid-containing cylinders of the prosthesis are of very bright signal intensity, with the relief valve assembly of low signal intensity.
Musculoskeletal infection: findings on magnetic resonance imaging.
Magnetic resonance imaging (MRI) can provide considerable useful information in cases of musculoskeletal infection, in particular demonstrating the extent of involvement of soft tissues and medullary bone. Differentiation between infected tissue and abscess is also possible with MRI, especially if contrast agent is administered. MRI therefore serves as an adjunct to other imaging modalities, especially in complex cases. This review covers various manifestations of musculoskeletal infection as depicted with MRI.
The emerging role of magnetic resonance imaging in rheumatology.
The role of magnetic resonance imaging (MRI) in imaging the central nervous system and in orthopedic radiology is now well accepted. Numerous applications of this technique also exist in the field of rheumatology, and it is anticipated that MRI will play an important part in the evaluation of treatments for the arthritides. In addition, MRI allows noninvasive investigation of other rheumatologic problems, such as avascular necrosis, tendon disorders and myopathy. This review outlines the current applications of MRI in rheumatologic practice.
Adamantinoma of the tibia: plain-film, computed tomography and magnetic resonance imaging appearance.
The authors describe the computed tomography (CT) and magnetic resonance imaging (MRI) characteristics of adamantinoma of the tibia in a 29-year-old man. Adamantinoma is a rare, aggressive osteolytic lesion occurring primarily in the diaphyseal portion of long bones. Because of its rarity the MRI features have been infrequently reported. In this case MRI provided more accurate information about the extent and invasiveness of the tumour than either plain radiography or CT.
Imaging after arthroplasty.
Arthroplasty is now an important and frequently performed orthopedic procedure. This article focuses on the imaging of abnormalities frequently encountered in patients who have undergone arthroplasty. The emphasis is on plain film analysis, although arthrography, computed tomography and nuclear medicine are also discussed. Among the problems illustrated are loosening of the prosthesis, component fatigue or failure, and infection. The authors recommend techniques to optimize imaging. Although most of the entities illustrated involve hip arthroplasty, the principles are valid for arthroplasty at other sites.
MRI evaluation of the knee meniscus.
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Diagnosis of osteoid osteoma using STIR magnetic resonance imaging.
Two patients with osteoid osteomas were evaluated with magnetic resonance imaging at 1.5 T using both conventional spin-echo (SE) and short TI inversion-recovery (STIR) sequences. On plain films the classic findings of a radiolucent nidus with a dense surrounding reactive zone of sclerosis were absent. The diagnosis was suspected on observing the presence of marked marrow oedema in the involved bone. Conventional SE images were unimpressive in detecting the bone marrow changes. Increased signal intensity indicating bone marrow oedema was striking on the STIR images and facilitated diagnosis. In cases of suspected osteoid osteoma which do not demonstrate the classic radiologic features, adding the STIR sequence to conventional SE magnetic resonance sequences to enhance detection of bone marrow change is recommended.
Intracavitary aspergilloma: transthoracic percutaneous injection of amphotericin gelatin solution.
For aspergillomas in patients with fibrocavitary lung disease, surgery is often not recommended. Injection or lavage of the cavities with solutions of potassium iodide or antifungal agents has had varying success and requires repeated sessions because of nonretention of the therapeutic agent within the cavity. In three patients with four aspergillomas, the authors used fluoroscopic or computed tomographic (CT) guidance to inject amphotericin in gelatin as a liquid that solidifies within the cavity at body temperature. The patients were followed up with serial chest radiography or CT. The mixture was successfully instilled in every case. Three of the four aspergillomas completely resolved within 3 months or less, with no evidence of recurrence at follow-up of 6-18 months. The remaining aspergilloma decreased in size, but the patient needed pneumonectomy because of recurrent hemoptysis within 6 months of amphotericin injection. Transthoracic instillation of a liquid mixture of amphotericin and gelatin that solidifies rapidly at body temperature may be useful as a one-step treatment for aspergillomas.
Safety of outpatient peripheral angioplasty.
PURPOSE: The safety of performing peripheral percutaneous angioplasty on an outpatient basis was studied. MATERIALS AND METHODS: A retrospective cohort study was conducted of all peripheral angioplastic procedures performed at one institution during a 4-year period. The 350 procedures in 235 patients included 84 inpatient cases, 141 outpatient cases, and 125 1-day-care cases (ie, procedures performed in patients transferred from other hospitals). RESULTS: The rates of major complications were 8.3% +/- 3.0 (mean +/- standard error) (n = 7) for inpatients. 5.0% +/- 1.8 (n = 7) for outpatients, and 5.6% +/- 2.1 (n = 7) for 1-day-care patients. Furthermore, 95% confidence intervals for the difference between complication rates were -10.3% and 3.5% for outpatient versus inpatient cases and -9.9% and 4.4% for 1-day-care versus inpatient cases. CONCLUSION: The risk of a major complication resulting from peripheral angioplasty in appropriately selected outpatients is no greater than it is for patients admitted for overnight observation.