ORBITAL PSEUDOTUMORS - VALUE OF SHORT INVERSION TIME INVERSION-RECOVERY MR-IMAGING

PURPOSE: To evaluate magnetic resonance (MR) signal intensities of orb ital pseudotumors on short inversion time inversion-recovery (STIR) im ages and to predict the effect of treatment. MATERIALS AND METHODS: Se quential MR examinations were performed in 17 patients with orbital ps eudotumors, before and after treatment. All patients underwent MR imag ing with T1- and T2-weighted spin-echo or fast spin-echo sequences, an d STIR sequences with two 0.5-T systems. Quantitatively and qualitativ ely, the differences in signal intensities among three therapeutic res ponse groups (good, mild, and no responses) were analyzed for each pul se sequence. RESULTS: Quantitatively, both contrast and contrast-to-no ise ratio on STIR images corresponded well to the results of response to therapy for all background markers; contrast and contrast-to-noise ratio values in the good response group were the largest, while those in the no response group were the smallest (P < .0001). Qualitatively, the signal intensities of the lesions in the good response group were interpreted as hyperintense to the cerebral cortex in 14 (93%) or 11 (73%) of 15 lesions by two observers, respectively, while in the no re sponse group, both observers assessed 16 (89%) of 18 lesions as hypo- or isointense to the muscle (P < .0001). CONCLUSION: STIR images showe d a variety of signal intensities in the lesions, and the signal inten sities on the STIR images helped predict the response to the therapy i n orbital pseudotumors.