MRI evaluation of mediastinal and thoracic inlet venous obstruction.

Fourteen patients with clinical and/or radiographic evidence of mediastinal or thoracic inlet venous obstruction were studied with magnetic resonance imaging (MRI) on a 0.35-T superconducting system using multislice spin-echo technique. The MRI examinations were retrospectively evaluated for their ability to provide information about the presence, level, and cause of venous obstruction, local extent of disease causing obstruction, and presence of collateral venous pathways. The results were compared to the information available from correlative studies including CT (11) and venography (four). In each instance, MRI provided detailed information about the precise site and extent of venous obstruction. The specific cause of the obstruction was suggested by MRI findings in one case of teratoma and in one case of postradiation fibrosis. Otherwise, all masses had relatively prolonged T1 T1 and T2 relaxation times and could not be differentiated on the basis of their and T2 relaxation times and could not be differentiated on the basis of their MRI appearances. Transaxial images most clearly and unequivocally depicted patent and obstructed superior vena cava (SVC). Enlarged venous collateral pathways were apparent in four cases. CT scans with intravenous contrast material in general provided information similar to that available with MRI, except in two cases where there was a discrepancy between CT and MRI concerning complete versus partial occlusion of the SVC. This initial study indicates that MRI can provide information about the presence, cause, and precise level of mediastinal and thoracic inlet venous obstruction.