MRI evaluation of residual mediastinal masses in Hodgkin's disease: A review of 40 patients with long-term follow-up

Purpose: To evaluate the role of MRI in distinguishing fibrous from active residual masses in treated Hodgkin's disease and to verify whether the use of I.V. paramagnetic contrast medium could provide additional information. Materials and methods: Forty patients with residual mediastinal masses underwent MRI after therapy (1, 6 and 12 months). A 1.5 T magnet, and T1 and T2-weighted sequences were used; in 37 patients I.V. contrast medium was administrated. Size, signal intensity on T2-weighted images and contrast enhancement of residual masses were evaluated. A long-term MRI follow-up (5 years) was then performed. Low signal intensity and low contrast enhancement were considered signs of inactive mass; homogeneous high signal intensity and remarkable contrast enhancement were indicative of active disease; inhomogeneous signal intensity and contrast enhancement were related to partial remission and/or presence of colliquative necrosis and/or radiotherapy induced inflammation. Results: We examined 32/40 patients after chemotherapy and 28, post chemotherapy and radiotherapy. 2 cases, classified as active pattern on the basis of T2-weighted sequence, showed colliquative inactive residues after Gd-injection. At the 6 months follow-up the use of contrast medium led to change in opinion about disease activity in 3 cases, proving to be useful in increasing MR specificity, easily distinguishing colliquative non enhancing areas within the residual mass. The long term follow-up confirmed the diagnosis. Conclusion: MRI is indicated when the activity of Hodgkin's disease has to be defined in residual masses. In some cases the I.V. administration of contrast medium may improve MRI diagnostic accuracy.