Musculoskeletal tumors: follow-up with MR imaging after treatment with surgery and radiation therapy.

Magnetic resonance (MR) imaging was used as a follow-up technique in 60 patients who underwent surgery and/or radiation therapy for primary malignant musculoskeletal tumors. MR imaging was performed on a 1.5-T imager with T1- and T2-weighted imaging sequences; MR imaging findings were confirmed by means of posttreatment surgery and histologic analysis or follow-up for at least 1 year. If a low-signal-intensity lesion was seen on T2-weighted images in a patient who had undergone radiation therapy or surgery, the patient usually did not have active tumor (sensitivity, 96%). If a high-signal-intensity lesion was seen after a patient had undergone only surgery, the patient had active tumor (six of six such cases). In patients who had undergone only radiation therapy, however, the presence of a high-signal-intensity lesion may indicate either active tumor or radiation-induced inflammatory changes. Thus, in such cases, differential diagnosis of active tumor may be difficult, if not impossible, to make from MR images.