[Study of cystic mediastinal lesions--diagnostic usefulness of magnetic resonance imaging].

We have recently operated 17 cases of cystic mediastinal lesions. A study was made here on their findings of magnetic resonance imaging (MRI). The MRI findings of all the cases revealed oval shaped mediastinal lesions. T2-weighted images showed the lesions to have extremely high signal intensity. Findings characteristic of each disease could also be observed. 1. Pericardial cyst. The cystic lesion was pericardial diverticulum located in cephalad recess of azygos vein (CRAzV) in 5 out of 6 cases. T1-weighted images revealed a mass lesion of low signal intensity with thin wall and enhancement effect by Gd-DTPA wasn't observed. 2. Bronchogenic cyst. In 2 out of 4 cases the cystic lesion was located in CRAzV and 2 cases in the posterior mediastinum. T1-weighted images revealed a mass lesion of high signal intensity and enhancement effect by Gd wasn't observed. 3. Thymic cyst. In all 3 cases the cystic lesion was located in the anterior mediastinum and even when large continuity with fatty tissue of the anterior mediastinum was observed. T1-weighted image revealed a mass lesion of low or iso-intensity and some parts of the wall were enhanced by Gd. 4. Cystic teratoma. In all 3 cases the cystic lesion was located in the anterior mediastinum. Even when the large part showed a cystic pattern, the wall had solid protuberant parts. This parts showed high signal intensity on T1-weighted images and were enhanced by Gd. 5. Cystic thymoma. We experienced a case of cystic thymoma. It presented a high signal intensity on T1-weighted images with a thick section in a part of the wall.(ABSTRACT TRUNCATED AT 250 WORDS)