[Magnetic resonance imaging in thoracic diseases]

Most all the thoracic structures are visible with magnetic resonance imaging: the mediastin, the myocardium including the endocardium and the pericardium, the pulmonary parenchyma and hile and the pleural walls. In cases of mediastrinal masses, T1 images clearly delimit their relations with neighbouring organs and vessels. The intensity of the signal is compared with that of the muscles on T1 weighted images of the preceding sections and T2 weighted images of fat. Images of aneurysms and chronic dissections can be synchronized with the ECG allowing three-dimensional measurement of the size and thickness of the vessel walls. Thrombi or extension to other vessels can also be recognized. Small hilar tumours can be differentiated from vessels but the scanner is better for analyzing systematization and bronchial lesions. For lung tissue itself, magnetic resonance imaging can detect nodules greater than one centimeter in diameter, but the low proton density and respiratory movements hinder spatial resolution. MRI is indicated for localizing tumours situated anteriorly or posteriorly or at the apex and to identify parietal extension of peripheral cancers. Spinal, vascular, pericardial, diaphragmatic and lymph node metastases can be recognized. MRI is the noninvasive method of choice for evaluating left ventricular masse, intra and paracardiac mass studies and for investigating congenital and acquired cardiomyopathies. Technical advances have made it possible to evaluate myocardial perfusion and heart function.