Lymphoma: monitoring tumor size and signal intensity with MR imaging.

To assess the potential value of magnetic resonance (MR) imaging in monitoring disease status, 34 patients with residual masses underwent MR imaging at sequential intervals. Patterns of signal intensity suggestive of active and inactive residual disease were compared to changes in tumor size. The signal intensity pattern was suggestive of persistent disease in 18 patients, even though tumor size was stable or decreased. Three of these patterns, seen within 6 months of initiation of therapy, were due to necrosis or inflammation. The MR imaging assessment of inactive disease was confirmed in 15 of the remaining 16 patients. In no case was an increase in tumor size seen in conjunction with a decrease in signal intensity. Because tumor size and signal intensity changes are not parallel in many cases, MR imaging may have a role in monitoring masses in patients with lymphoma. Signal intensity patterns, however, reflect gross histologic characteristics and cannot be considered specific, especially in the first 6 months after initiation of therapy.