MR Imaging in the Follow-Up Evaluation of Aggressive Soft Tissue Tumors.

Although newer imaging techniques aid in the diagnosis of soft tissue sarcomas and current surgical procedures and adjunct therapy decrease the incidence of their recurrences when patients are referred to oncologic centers, the majority of these tumors are suboptimally evaluated in general practice with frequent recurrences. Close surveillance of these patients is necessary for early recognition and treatment of recurrent disease. This article describes an organized, stepwise magnetic resonance imaging evaluation of these patients after surgery and radiation therapy. The initial sequence should be T2-weighted. Low signal intensity or diffuse high signal intensity without mass on T2-weighted sequence excludes recurrence in 99% of patients. A high signal intensity mass, however, should be studied with bolus injection of contrast medium. Although standard contrast-enhanced MR imaging differentiates the non-enhancing hygroma or hematoma from the enhancing recurrence or pseudotumor, dynamic contrast-enhanced MR imaging is required to distinguish the rapidly enhancing recurrent tumor from the slowly enhancing pseudotumor of inflammation.