Orbital involvement in Wegener granulomatosis: MR findings in 12 patients.

PURPOSE: Our goal was to characterize the MR features of orbital Wegener granulomatosis (WG).

METHOD: Twelve patients with pathologically proven WG were studied with MRI. Enhanced and unenhanced T1-weighted sequences with conventional and fat-suppressed techniques were used. T2-weighted images were also obtained. Signal intensity measurements were made in each orbital lesion on the T2-weighted images and compared with that of normal fat. The degree of enhancement was also evaluated by measuring the change in signal intensity of each lesion between the unenhanced 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-fat-suppressed T1-weighted sequences provided the best contrast between lesion and normal structures. All of the WG lesions enhanced, but the degree of enhancement varied. The enhancement characteristics were best appreciated on the fat-suppressed T1-weighted technique.

CONCLUSION

MRI is an excellent imaging modality to evaluate orbital involvement in WG. A marked decrease in the T2 signal is a characteristic feature of this entity. The unenhanced, non-fat-suppressed T1-weighted sequence is the preferred method for lesion detection and for definition of the pattern of anatomic involvement when utilizing MRI.