Contrast-Enhanced Fat-Suppression MR Imaging of Avascular Necrosis of Femoral Head

ABSTRACT

PURPOSE: To evaluate the findings and role of contrast-enhanced fat suppression MR imaging in avascular necrosis(AVN) of the femoral head. MATERIALS AND METHODS: In 15 patients with AVN of the femoral head, MR T1-weighted and T2-weighted images and contrast-enhanced fat-suppression T1-weighted images were obtained, and the findings were re-viewed. Early and advanced groups were classified on the basis of clinical findings and imaging, and the en-hancement pattern was classified as either type I, rim enhancement; type II, surrounding diffuse enhance-ment; type III, intralesional enhancement; or type IV, II + III. RESULTS: Twenty-four cases of AVN of the femoral head were detected; in nine patients, lesions were bilateral. Eight cases occurred in the early group and 16 in the advanced. All eight in the early group showed the "double line sign" on T2-weighted images, with a type-I enhancement pattern. In the advanced goup, type II(8/16) and type IV(8/16) enhancement patterns were seen. Among the cases showing the type-IV pattern, the intrale-sional enhancing area showed low signal intensity on T1-weighted images and isosignal intensity on T2 weighted in one case, and low signal intensity on T1-weighted images and high signal intensity on T2-weight-ed in the other cases. There was no difference in the extent of the disease before and after enhancement. CONCLUSION: Contrast-enhanced fat-suppression MR images may be helpful in evaluating the extent of AVN of the femoral head and predicting the histopathologic findings of the disease