MR imaging of eosinophilic granuloma: report of 11 cases.

The findings in 11 patients with histologically proven eosinophilic granuloma (EG) examined by magnetic resonance imaging (MRI) are described. In contrast with the variable appearance of EG on conventional radiography and computed tomography (CT), relatively constant features--intermediate to high signal intensity on T1-weighting, high signal intensity on T2-weighting, marked enhancement--were found on MRI. MRI was superior to other imaging methods in demonstrating bone marrow involvement and any accompanying soft tissue mass or inflammation. Intermediate to high signal intensity on T1-weighting and marked contrast enhancement could not be "explained" by histological findings. Prediction of the evolutionary phase of EG by MRI remains questionable because of the phase I (proliferative) histology of all 11 lesions.