Utility of opposed-phase magnetic resonance imaging in differentiating sarcoma from benign bone lesions

PURPOSE To investigate the utility of opposed-phase magnetic resonance imaging (OP MRI) in differentiating malignant from benign bone lesions. MATERIALS AND METHODS MRI scans of musculoskeletal lesions including opposed-phase imaging sequences were reviewed by both an experienced musculoskeletal attending radiologist, and a second year radiology resident. The change in signal from IP to OP images was measured. The reviewers' evaluation of the lesions based on T1 and T2-weighted images was compared to their evaluation with inclusion of the OP sequences. RESULTS Twenty-seven lesions in bone were analyzed: 4 malignant primary bone lesions, 3 malignant soft tissue lesions to bone, 3 metastases from visceral malignancies, and 17 benign bone lesions. Benign lesions of bone dropped in signal on OP imaging by an average of 37.1%. Five of the benign lesions decreased in signal by less than 20%, and two increased. Malignant bone lesions dropped in signal by an average of 0.69% with one of the ten lesions showing a greater than 20% drop. When OP sequences were included, concern for malignancy decreased in benign lesions and increased in malignant lesions, for both the resident and attending. Compared with standard MRI, inclusion of these sequences increased the overall confidence in diagnosis for both reviewers. CONCLUSION Opposed-phase imaging is helpful in differentiating benign from malignant lesions in bone. Confidence in diagnosis rose for both the attending and the resident as result of the inclusion of OP sequences.