Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Mar 1996
Randomized Controlled Trial Comparative Study Clinical TrialProspective comparison of helical CT and MR imaging in clinically suspected acute pulmonary embolism.
The purpose of this study is to compare sensitivity and specificity of helical CT and MR imaging for detecting acute pulmonary embolism(PE). Patients who were suspected clinically of having PE were randomly assigned to undergo either helical contrast-enhanced CT or gradient-echo MR (if one modality was contraindicated, the patient was assigned to the other.) Patients were considered to have PE if they had: 1) high-probability V-Q scan and low clinical probability of PE; 2) pulmonary angiogram positive for PE. Patients were considered not to have PE if they had either:1)normal V-Q scan; 2) low probability V-Q scan and low clinical probability of PE; or 3) pulmonary angiogram negative for PE. ⋯ Experience with vascular MR and enhanced CT influenced diagnostic accuracy. For the two vascular MR experts, average sensitivity and specificity of MR were 71% and 97%, and of CT 73% and 97%. In this pilot study, when CT and MR were interpreted with comparable expertise, they had similar accuracy for detecting pulmonary embolism.
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J Magn Reson Imaging · Mar 1996
Malignant lesions of the liver with high signal intensity on T1-weighted MR images.
Our purpose was to identify the histologic types of malignant liver lesions with high signal intensity (SI) on T1-weighted images and to describe the MR imaging features. Thirteen patients with malignant liver lesions high in SI on T1-weighted images were studied with a 1.5-T MR imager using pre- and serial postcontrast spoiled gradient-echo (SGE) sequences (all patients), T2-weighted fat-suppressed spin-echo sequences (all patients), precontrast T1-weighted fat-suppressed spin-echo sequences (five studies in five patients), and precontrast out-of-phase SGE sequences (seven studies in six patients). Images were reviewed retrospectively to determine number of lesions; lesion size; SI of lesions on T1-weighted, T2-weighted, and fat-attenuated T1-weighted images; distribution of high SI in lesions on T1-weighted images; and tumor enhancement pattern. ⋯ In one patient with melanoma metastases and one patient with multiple myeloma nodules, appreciably more lesions were detected on out-of phase SGE images. Causes of hyperintensity were considered to be either fat, melanin central hemorrhage, or high protein content, all of which may be seen in a variety of tumors. Fat-attenuation techniques are helpful in the detection of these lesions.
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J Magn Reson Imaging · Jan 1996
Clinical TrialMR imaging of silicone breast implants: evaluation of prospective and retrospective interpretations and interobserver agreement.
MR imaging was used to evaluate the integrity of silicone breast implants in 54 women with 108 implants. MR images were interpreted by relatively inexperienced readers who tried to reproduce the experiences reported in the literature. The study examines the interobserver agreement using different diagnostic signs and the influence of experience on interpretation errors. ⋯ The sensitivities of the individual signs were less than the overall retrospective sensitivity. With experience, the sensitivity improved from 87% to 93% and the specificity improved from 78% to 92%. This study helps substantiate the use of diagnostic signs used by other authors to detect silicone loss from breast implants by MR imaging; however, questions remain as to the clinical role of MR imaging in evaluating implants for silicone loss.
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J Magn Reson Imaging · Nov 1995
Phase-contrast echo-planar MR imaging: real-time quantification of flow and velocity patterns in the thoracic vessels induced by Valsalva's maneuver.
Although the clinical manifestations of Valsalva's maneuver are well known, the associated hemodynamic changes in the great vessels have not been extensively studied and documented. In each of six healthy subjects, we evaluated three "quasi-steady-state" phases of Valsalva's maneuver: (1) during normal respiration, (2) during late strain, and (3) 4 seconds after strain release. ⋯ MR velocity measurements agreed with echocardiographic data and supplied additional information on flow and morphology. EPI showed a reduction in venous return during Valsalva's maneuver by simultaneously assessing flow, velocity, and vessel morphology; this technique appears to be useful in the analysis of flow dynamics of the great vessels.
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J Magn Reson Imaging · Sep 1994
Ex vivo evaluation of ferromagnetism, heating, and artifacts produced by heart valve prostheses exposed to a 1.5-T MR system.
Ex vivo testing techniques were used to determine the ferromagnetic qualities of, presence of heating in, and artifacts produced by 13 different heart valve prostheses exposed to a 1.5-T (64-MHz) magnetic resonance (MR) system. None of the heart valve prostheses showed a measurable deflection in the 1.5-T static magnetic field. ⋯ The largest temperature changes measured during a "worst case" MR imaging sequence (estimated average specific absorption rate, 2.5 W/kg; estimated spatial peak specific absorption rate, 7.6 W/kg) were +0.2 degree C with the implant imaged "in air" and +0.3 degrees C with the implant imaged in normal saline. Therefore, MR procedures performed with a 1.5-T (64-MHz) MR system may be performed safely in patients with any of the 13 different heart valve prostheses evaluated in this study.