[Emphysematous pyelonephritis: apropos of 4 cases]. / Pyélonéphrite emphysémateuse: à propos de quatre observations.

PURPOSE: The propose of this study was to describe the imaging findings in four patients with emphysematous pyelonephritis and to perform a review of the literature. MATERIAL AND METHODS: Four cases of emphysematous pyelonephritis are presented. US and CT examinations were available for all patients. RESULTS: Gas within the kidney may be diagnosed by plain film or rarely by ultrasound, but its location and its extent are best evaluated by CT. A review of the literature shows that emphysematous pyelonephritis is a rare and life-threatening infection typically occurring in diabetic patients. CONCLUSION: CT is useful for diagnosing emphysematous pyelonephritis, especially when symptoms fail to resolve promptly with medical therapy.

Regional heterogeneity of human myocardial infarcts demonstrated by contrast-enhanced MRI. Potential mechanisms.

BACKGROUND: Myocardial reperfusion is pivotal to the prognosis of patients with acute myocardial infarction. In these patients, coronary flow is generally assessed by angiography and tissue perfusion by tracer scintigraphy. This study was designed to examine whether magnetic resonance imaging (MRI) provides information on myocardial perfusion and damage beyond that supplied by angiography and thallium scintigraphy after acute myocardial infarction. METHODS AND RESULTS: Twenty-two patients with recent myocardial infarction had ECG, echocardiography, coronary angiography, and fast contrast-enhanced MRI. Twelve patients also had exercise thallium scintigraphy. Time-intensity curves obtained from infarcted and noninfarcted regions were correlated with coronary anatomy and left ventricular function. Two perfusion patterns were observed in infarcted regions by comparison with the normal myocardial pattern. All patients but 1 had persistent myocardial hyperenhancement within the infarcted region up to 10 minutes after contrast. In 10 patients, this hyperenhanced region surrounded a subendocardial area of decreased signal at the center of the infarcted region associated with coronary occlusion at angiography, Q waves on ECG, and greater regional dysfunction by echocardiography. Moreover, the extent and location of the MRI abnormalities correlated well with the extent and location of the fixed single-photon emission computed tomography thallium defects. CONCLUSIONS: Large human infarcts, associated with prolonged obstruction of the infarct-related artery, are characterized by central dark zones surrounded by hyperenhanced regions on MRI. Conversely, reperfused infarcts with less regional dysfunction have uniform signal hyperenhancement. The MRI hyperenhanced segment correlates well with the fixed scintigraphic defect in patients with acute myocardial infarction.

Impact of semiautomated versus manual image segmentation errors on myocardial strain calculation by magnetic resonance tagging.

RATIONALE AND OBJECTIVES: Accurate image segmentation is essential for the study of mechanical properties of the myocardium by tagged magnetic resonance imaging (MRI). The relative accuracy of three methods of segmentation of myocardial borders and tags and their impact on myocardial strain calculations were evaluated. METHODS: Radially tagged, spin-echo magnetic resonance (MR) images of dog hearts were segmented manually, automatically, and semiautomatically. The variability of segmentation methods was separately determined for myocardial contours and tags. Error propagation assessment for strain calculation was estimated. RESULTS: The variability of the segmentation of the contours was five times greater than that of the tags. The error propagation is nonuniform in all directions, maximal for the radial component of strain. CONCLUSION: Errors in the segmentation of myocardial contours are significantly greater than those of the tags. Strain calculations should be based solely on segmentation of MR tags to avoid significant errors, particularly in radial strain estimates.