ORBITAL INVOLVEMENT IN WEGENER GRANULOMATOSIS - MR FINDINGS IN 12 PATIENTS

Purpose: Our goal was to characterize the MR features of orbital Wegen er granulomatosis (WG). Method: Twelve patients with pathologically pr oven WG were studied with MRI. Enhanced and unenhanced T1-weighted seq uences with conventional and fat-suppressed techniques were used, T2-w eighted images were also obtained, Signal intensity measurements were made in each orbital lesion on the T2-weighted images and compared wit h that of normal fat. The degree of enhancement was also evaluated by measuring the change in signal intensity or each lesion between the un enhanced and enhanced studies. Results: Seventeen orbital lesions were identified in the 12 patients. Fifteen of the lesions examined by T2- weighted sequences demonstrated a marked decrease in signal intensity. The unenhanced, non-far-suppressed T1-weighted sequences provided the best contrast between lesion and normal structures, All of the WG les ions enhanced, but the degree of enhancement varied. The enhancement c haracteristics were best appreciated on the fat-suppressed T1-weighted technique. Conclusion: MRI is an excellent imaging modality to evalua te orbital involvement in WG. A marked decrease in the T2 signal is a characteristic feature of this entity. The unenhanced, non-fat-suppres sed T1-weighted sequence is the preferred method for lesion detection and for definition of the pattern of anatomic involvement when utilizi ng MRI.