Malignant lymphoma: MR tomographic findings of residual mediastinal space-occupying lesions.

Purpose: Evaluation of MR imaging in patients with Hodgkin's lymphoma and h igh grade non-Hodgkin's-lymphoma and mediastinal residual mass after first line chemotherapy. Materials and Methods: MR imaging (1.5 T) was performed in 36 patients (Hodgkin's lymphoma n = 26, NHL n = 10) after first line che motherapy). Twenty patients had inactive residual mass, 16 patients had res idual lymphoproliferative lesions. T-1- and T-2-weighted spin echo images w ere visually analysed by a score index (range 1- 5) as well as quantificati on of enhancement by signal-intensity-ratios (SImax/SIplain). Results: For the differentiation between residual lymphoproliferative activity and inact ive residual mass, the highest accuracy was obtained for the signal intensi ty of residual mass on T-2-w-SE compared to pectoralis muscle (94% sensitiv ity, 80 % specificity, likelihood ratios: 4.0 [LR+]; 0.3 [LR-]).The cut-off value of the SI ratio was calculated retrospectively at 1.96 (p>0.05). Con clusions: Differentiation between inactive (fibrotic) and lymphoproliferati ve (active) residual mediastinal mass is possible by MR imaging using as pa rameter the size reduction after therapy and the signal intensity on T-2-w- SE in comparison to pectoralis muscle. Thus study suggests an additional va lue using the SI ratio for the differentiation.