MR imaging of xanthogranulomatous pyelonephritis

The magnetic resonance (MR) appearance of a case of xanthogranulomatous pyelonephritis is described and compared with CT and surgical findings. Both CT and MR were comparable in displaying the morphology of this uncommon renal abnormality.     

Alexander disease: diagnosis with MR imaging

BACKGROUND AND PURPOSE: To date, the demonstration of Rosenthal fibers on brain biopsy or autopsy specimens is considered a prerequisite for a definitive diagnosis of Alexander disease. We initiated a multiinstitutional survey of MR abnormalities in both presumed and confirmed cases of Alexander disease to assess the possibility of an MR-based diagnosis. METHODS: MR imaging studies in three patients with an autopsy-based diagnosis of Alexander disease were analyzed to define MR criteria for the diagnosis. These criteria were then applied to 217 children with leukoencephalopathy of unknown origin. RESULTS: Five MR imaging criteria were defined: extensive cerebral white matter changes with frontal predominance, a periventricular rim with high signal on T1-weighted images and low signal on T2-weighted images, abnormalities of basal ganglia and thalami, brain stem abnormalities, and contrast enhancement of particular gray and white matter structures. Four of the five criteria had to be met for an MR imaging-based diagnosis. In a retrospective analysis of the MR studies of the 217 patients, 19 were found who fulfilled these criteria. No other essentially new MR abnormalities were found in these patients. In four of the 19 patients, subsequent histologic confirmation was obtained. The clinical symptomatology was the same in the patients with and without histologic confirmation and correlated well with the MR abnormalities. MR abnormalities were in close agreement with the known histopathologic findings of Alexander disease. CONCLUSION: The defined criteria are sufficient for an in vivo MR imaging diagnosis of Alexander disease; only in atypical cases is a brain biopsy still necessary for a definitive diagnosis.     

髌骨软化症的MRI研究

目的：总结髌骨软化症（ＣＭＰ）的ＭＲＩ表现，研究ＭＲＩ对ＣＭＰ的诊断作用。材料与方法：对９７例拟诊ＣＭＰ膝关节的ＭＲＩ表现和关节镜检查所见进行对照研究。结果：ＣＭＰ的ＭＲＩ表现为：（１）髌软骨内尖刺状或斑片状低信号；（２）软骨局部隆起，其内信号强度减低；（３）软骨表面不光滑；（４）软骨变薄；（５）软骨缺损、骨质暴露。以关节镜为标准ＭＲＩ诊断ＣＭＰ的敏感性为９０．７％，特异性为７８．６％，准确性为８５．６％。结论：ＭＲＩ能显示ＣＭＰ的病理变化；在病变晚期，与关节镜的诊断符合性好；在病变早期，ＭＲＩ在诊断上有一定优势     

Penetrating aortic ulcers: diagnosis with MR imaging

The authors studied seven patients with penetrating aortic ulcers with use of magnetic resonance (MR) imaging. All patients were evaluated for acute chest symptoms, and the presence of aortic ulcers was confirmed by means of angiography in all seven patients. Five patients also underwent computed tomography (CT). Three patients underwent surgical repair of the thoracic aorta. MR findings included intramural hematoma and focal aortic wall ulceration in four patients, focal ulceration in one, focal intramural hematoma in one, and focal intramural hematoma with rupture in one. The diagnosis of intramural hematoma was made by the detection of increased signal intensity on T1- and T2-weighted MR images. MR imaging was superior to angiography in depicting the extent of intramural thrombus, although one ulceration diagnosed at angiography was missed at MR imaging. MR imaging was superior to CT in differentiating acute intramural hematoma from atherosclerotic plaque and chronic intraluminal thrombus, although it did not depict displaced intimal calcification in one patient with extensive intramural hematoma.     

Fixed spinal cord: diagnosis with MR imaging

Pulsatile motion of the spinal cord was examined with phase imaging techniques. Sagittal images of the spinal cord were obtained at different times of the cardiac cycle in healthy volunteers, as well as in patients in whom the spinal cord either was tethered, was compressed, or contained an intramedullary lesion. Pulsatile velocity changes of the spinal cord, observed on the phase images, were most marked at the cervical-upper thoracic level. Cord motion was found to be significantly decreased in cases in which the cord was either tethered or compressed. Cord enlargement due to an intramedullary lesion generally did not lead to decreased cord motion. Imaging of pulsatile cord motion may be clinically useful in evaluating diseases restricting cord motion or changing the status of parenchymal compliance.     

Chondromalacia patellae: diagnosis with MR imaging.

Most previous studies of MR imaging for detection of chondromalacia have used T1-weighted images. We correlated findings on axial MR images of the knee with arthroscopic findings to determine MR findings of chondromalacia patellae on T2-weighted and proton density-weighted images. The study population included 52 patients who had MR examination of the knee with a 1.5-T unit and subsequent arthroscopy, which documented chondromalacia patellae in 29 patients and normal cartilage in 23. The patellar cartilage was assessed retrospectively for MR signal and contour characteristics. MR diagnosis based on the criteria of focal signal or focal contour abnormality on either the T2-weighted or proton density-weighted images yielded the highest correlation with the arthroscopic diagnosis of chondromalacia. When these criteria were used, patients with chondromalacia were detected with 86% sensitivity, 74% specificity, and 81% accuracy. MR diagnosis based on T2-weighted images alone was more sensitive and accurate than was diagnosis based on proton density-weighted images alone. In conclusion, most patients with chondromalacia patellae have focal signal or focal contour defects in the patellar cartilage on T2-weighted MR images. These findings are absent in most patients with arthroscopically normal cartilage.     

Fungal sinusitis: diagnosis with CT and MR imaging

Of 293 patients who underwent computed tomography (CT), surgery, and pathologic examination for chronic sinusitis, 25 had a diagnosis of fungal sinusitis at pathologic examination. Of these, 22 had foci of increased attenuation at CT (in four patients the mean representative CT number [Hounsfied unit] was 122.2 HU [SD, 8.2 HU]), and three did not. Of the 22, 19 patients (76%) met the CT criterion of this study (there was a 12% false-positive and a 12% false-negative diagnostic rate). Six of the 19 patients and one additional patient underwent magnetic resonance (MR) imaging, and all demonstrated remarkably hypointense signal characteristics on T2-weighted images. The findings at MR imaging therefore appear more characteristic of fungal sinusitis than the findings at CT. Furnace atomic absorption spectrometry showed increased concentrations of iron and manganese in mycetoma compared with their concentrations in bacterially infected mucus. This finding and the presence of calcium in the fungal concretion may explain the hypointense T2-weighted signal on MR images.     

Adenomyosis and leiomyoma: differential diagnosis with MR imaging

To assess the capability of magnetic resonance (MR) imaging to enable differentiation of adenomyosis from leiomyoma, a prospective study was performed in 21 premenopausal patients with a strong clinical suggestion of adenomyosis. Histologic findings from hysterectomy (19 patients) and biopsy specimens (two patients) showed that eight patients had adenomyosis (three focal, five diffuse) and 12 had leiomyomas (five of the 12 also had microscopic foci of adenomyosis); one patient had a normal uterus. All eight cases of adenomyosis were correctly diagnosed from MR images. On T2-weighted MR images, diffuse adenomyosis appeared as a thickening of the junctional zone, whereas focal adenomyosis appeared as a low-signal-intensity mass poorly marginated from the adjacent myometrium. Ten of the 12 leiomyomas were correctly diagnosed from MR images. In the other two cases of leiomyoma, differentiation between focal adenomyosis and leiomyoma was not possible. Microscopic foci of adenomyosis were not demonstrated with MR imaging.     

Cardiac rhabdomyosarcoma: diagnosis by MR imaging

We report a case of cardiac rhabdomyosarcoma the initial clinical features of which were pericardial effusion, clinical symptoms of congestive heart failure and probable pulmonary thromboembolism, in which echocardiography constituted the first approach to the diagnosis of cardiac tumor and MRI confirmed it, precisely delimiting the tumoral extension and possible infiltration of pericardiac structures. A brief literature review of this entity is given, the MRI findings obtained in our case are described, and we discuss the advantages and limitations of this technique as compared with other alternatives of image diagnosis. Received: 5 November 1997; Revision received: 6 April 1998; Accepted: 7 July 1998     

Müllerian duct cyst: diagnosis with MR imaging

The value of magnetic resonance (MR) imaging in diagnosing clinically suspected müllerian duct cysts was assessed in six patients. MR imaging correctly demonstrated the abnormality to be intraprostatic, consistent with the diagnosis of müllerian duct cysts in four patients, and allowed the diagnosis to be excluded in the other two. The demonstration of prostatic zonal anatomy, the ability to obtain direct images in all three orthogonal planes, and a large field of view make MR imaging valuable in the study of suspected müllerian duct cysts.     

Osteomyelitis: characteristics and pitfalls of diagnosis with MR imaging

Prospective and retrospective magnetic resonance (MR) imaging (0.35-T) interpretations were compared with final diagnoses in 110 patients suspected to have osteomyelitis. Diagnostic criteria of dark marrow on T1-weighted images and bright marrow on short-tau inversion-recovery images yielded a prospective sensitivity of 98% and a prospective specificity of 75%. Sixty percent of uncomplicated septic joint effusions demonstrated abnormal marrow signal intensity that was mistaken for osteomyelitis. Retrospective review revealed that overall specificity could be improved to 82% without loss of sensitivity if increased marrow signal intensity on T2-weighted images were included as an additional criterion. Specificity may be further increased by use of knowledge of morphologic patterns that distinguish various forms of osteomyelitis. Ten patients (9%) had potential pitfall diagnoses (eg, fracture, infarction, healed infection) that mimic osteomyelitis. MR imaging can be sensitive and specific for osteomyelitis if characteristic appearances and pitfall diagnoses are incorporated into the diagnostic criteria.