MAGNETIC-RESONANCE-IMAGING IN THORACIC DI SEASES

Most all the thoracic structures are visible with magnetic resonance i maging : the mediastin, the myocardium including the endocardium and t he pericardium, the pulmonary parenchyma and hile and the pleural wall s. In cases of mediastrinal masses, T1 images clearly delimit their re lations with neighbouring organs and vessels. The intensity of the sig nal 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 thre e-dimensional measurement of the size and thickness of the vessel wall s. Thrombi or extension to other vessels can also be recognized. Small hilar tumours can be differenciated from vessels but the scanner is b etter for analyzing systemization and bronchial lesions. For lung tiss ue 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 ident ify parietal extension of peripheral cancers. Spinal, vascular, perica rdial, diaphragmatic and lymph node metastases can be recognized. MRI is the noninvasive method of choice for evaluating left ventricular ma sse, intra and paracardiac mass studies and for investigating congenit al and acquired cardiomyopathies. Technical advances have made it poss ible to evaluate myocardial perfusion and heart function.