MR appearance of fibrous dysplasia.

Magnetic resonance (MR) imaging is utilized in diverse clinical circumstances for evaluation of the musculoskeletal system. Consequently, common benign skeletal lesions may be detected incidentally following MR scan obtained for unrelated reasons. The spectrum of MR appearances of fibrous dysplasia has not been previously reported. We retrospectively reviewed all radiologic images (including the MR scans) of 11 sites of fibrous dysplasia encountered in seven patients. On MR, the fibrous dysplastic lesion causes an "expanded" bony contour and is characterized by decreased signal on T1-weighted image. The signal on T2-weighted MR scan is variable, however. Since fibrous dysplasia is a (relatively) common skeletal lesion that can be encountered incidentally, all radiologists should be familiar with its MR appearance. Furthermore, in the unlikely possibility of surgical intervention, MR is useful in determining the extent of disease within the affected bone and planning the preoperative strategy.