[Diagnostic radiology in mediastinal disorders : technical progress and current strategy (author's transl)].

After a brief reminder of recent progress in radiological methods in the diagnosis of mediastinal disorders, the authors study the contribution of Computerised Axial Tomography (T.D.M.). The advantages of T.D.M. in mediastinal disease rest on two characteristics : the morphological study of the mediastinum is made easier by the display of transverse axial cuts with nothing superimposed; the density measurements can distinguish between opacities which would appear similar on conventional radiology. Three facts have been established by the authors : T.D.M. raises the diagnostic sensitivity of radiology; in distinguishing between fatty, watery, vascular and solid tumours, it increases aetiological specificity; it simplifies the diagnostic approach while increasing the efficiency of radiology and the importance of its role in therapeutic decisions. In a typical case where one has just discovered an abnormal mediastinal opacity (and in whom a gastro-intestinal primary has been excluded), T.D.M. should be the first examination after standard radiography, because its results determine the remaining investigation. T.D.M. is specially indicated in evaluating a myasthenic or when investigating an anomaly in the infero-posterior mediastinum. A few cases do not entirely fit in to this schema, because of a particular clinical or radiological situation such as : mediastinal adenopathy; the assessement of the extent of a bronchogenic carcinoma; anterior cardio-phrenic opacities. The examination of the hila again has its limits when the abnormal opacity is small as there are errors in the technique due to the effects of incomplete volume. Finally, there remains the improved cost-effectiveness of the radiological examination of the mediastinum with the rational use of T.D.M.