High signal intensity lesions of the chest in MR imaging.

The majority of pathologic lesions in the lung and mediastinum have relatively long T1 and T2 relaxation times and consequently yield medium to low signal intensity on T1-weighted images. Pulmonary lesions with high signal intensity on T1-weighted images are unusual and raise a special group of diagnostic considerations. In the current study, a mass with a lesion/fat signal intensity ratio of greater than 0.7 on a T1-weighted sequence was considered high signal intensity. The nature of these masses was ganglioneuroma or ganglioneuroblastoma (n = 3), atrial lipoma (lipomatous atrophy of the interatrial septum) (n = 3), pheochromocytoma (n = 2), bronchogenic cyst (n = 2), lymphangioma (n = 1), teratoma (n = 1), and a variety of primary and metastatic tumors of the mediastinum and lung. A single pathologic structure of these lesions was not present, but rather several underlying tissue compositions were noted, including fat, subacute hemorrhage, myxoid material, and cellular composition with high cytoplasmic/nuclear ratio. Thus, high signal intensity lesions of the thorax on T1-weighted images should suggest a number of differential diagnoses.