MRI characterization of residual mediastinal masses in Hodgkin’s disease: 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 employment of paramagnetic contrast medium could provide additional information for such a distinction. Material and Methods: Forty patients with mediastinal residue larger than 1.5 cm underwent MRI 1, 3, 6 and 12 months after the end of prescribed therapy. MRI examinations were performed on 0.5 and 1.5 T systems, using SE T1 and T2-weighted sequences. Each time the residual mass was evaluated for size and signal intensity on SE T2-weighted images and on contrast-enhanced SE T1-weighted images. We compared our results with long term clinical follow–up (performed 5 to 6 years later), which was our gold-standard. Results: We examined 28 stage II, 11 stage III and 1 stage IV patients. Low signal intensity and low contrast enhancement were considered as inactive residue, homogeneous high signal intensity and high contrast enhancement as active residual disease and heterogeneous signal intensity and heterogeneous contrast enhancement as partial remission or as necrotic/inflammatory phenomena. In 3 cases, the employment of contrast medium let us change our opinion about disease activity, so increasing MR specificity, distinguishing colliquative areas within the residual mass. Conclusions: MRI diagnostic accuracy with respect to the gold standard is higher if the examination is performed at least 6 months after the end of treatment (false positive results minimized). Moreover, the accuracy seems to be slightly higher in the evaluation of stage II disease, with respect to stage III.