Differentiation between Ovarian Fibroma and Subserosal Leiomyoma by MR Imaging

PURPOSE: To evaluate the findings and differential points of ovarian fibroma and subserosal leiomyoma, as seen on MR images. MATERIALS AND METHODS: The MR imaging findings of 31 surgically confirmed cases of ovarian fibroma(n=6) and subserosal leiomyoma (n=25 ; 28 lesions) were evaluated. Multiplanar T1- and T2-weighted and postcon-trast T1-weighted images were obtained using a 1.5T MR unit, and histologic examination was also performed. The MR findings were analyzed in terms of signal intensity, the presence and definition of margin, the histo-logic finding of hyperintense lesion on T2-weighted images, the presence of the bridging vessel sign, degree of enhancement, and the presence of ipsilateral ovary and ascites. RESULTS: Both fibromas and leiomyomas showed hypo-or isointensity compared with uterine myometrium on T1-weighted images and compared with skeletal muscle on T2-weighted images. The latter revealed intratu-moral hyperintense lesions in most cases of ovarian fibroma and subserosal leiomyoma. Three of four ovarian fibromas had a well defined margin after cystic change, but in 24 of 26 subserosal leiomyomas the margin was ill defined. The "bridging vessel sign" was visible only in subserosal leiomyomas (22/28), and in all cases the enhancement of ovarian fibromas were less than that of myomtetrium. Subserosal leiomyomas (12/28), seen on enhancement as isointense or hyperintense to myometrium, showed a greater degree of enhancement than ovarian fibromas (0/6). Ipsilateral ovary was rarely seen in ovarian fibromas (1/6), but commonly seen in sub-serosal leiomyomas (20/25). Ascites was present in one case of ovarian fibroma. CONCLUSION: A defined margin of an intratumoral hyperintense lesion, as seen on T2-weighted images, and the presence or absence of the "bridging vessel sign" and ipsilateral ovary are useful signs when differentiating be-tween ovarian fibromas and subserosal leiomyomas.

MR Imaging Findings of Renal Infarction Induced by Renal Artery Ligation in Rabbits: The Usefulness of Diffusion-weighted Imaging

PURPOSE: To assess the usefulness of diffusion-weighted imaging(DWI) in evaluating serial parenchymal changesin renal infarction induced by renal artery ligation, by comparing this with the conventional spin echo techniqueand correlating the results with the histopathological findings. MATERIALS AND METHODS: In 22 rabbits, renalinfarction was induced by ligation of the renal artery. Spin-echo T1-weighted imaging(T1WI), turbo spin-echo(TSE)T2-weighted imaging(T2WI), and DWI were performed, using a 1.5-T superconductive unit, at 30 minutes, 1 hour, 2,3, 6, 12 and 24 hours, and 2, 3, 7 and 20 days after left renal artery ligation. Changes in signal intensity onT1WI, T2WI, and DWI were correlated with histopathologic findings. RESULTS: On MR images obtained 30 minutesafter ligation, the signal intensity of affected kidney was not significantly different from that of contralateralkidney, as seen on T1WI and T2WI, but was noticeably higher on DWI. On T2WI, the signal intensity ratio(SIR) wasslightly higher over time from 30 minutes to 2 days after ligation, and then decreased slightly. The SIR on DWIincreased abruptly at 30 minutes, remained high until 12 hours, and then fell, returning to close to the normalrange at between 2 and 3 days. It fell further, below the normal range, until 20 days after ligation. The mainhistopathologic findings after ligation were congestion and swelling of renal tubules (1-6 hours after ligation),degeneration and necrosis of renal tubules (12 hours - 2 days), coagulation necrosis of renal tubules(3 days),collection of cellular debris between renal tubules (7 days), and proliferation of fibroblast between renaltubules (20 days). CONCLUSION: Diffusion-weighted imaging is useful for the detection of hyperacute renalinfarction, and the apparent diffusion coefficient may provide additional information concerning its evolution.