[Procedure and purpose of thoracic radiology (author's transl)].

X-ray investigations of patients with symptoms of thoracical illness require the posterior-anterior and the lateral projections as well. The lateral projection is not necessary for routine screening examinations of patients younger than 40 years. Fluoroscopy is used in appropriately one third of the patients to clarify or to bring additional information to the diagnosis. X-rays taken in inspiration and exspiration help to disclose malfunctions in breathing of one or both lungs. X-rays taken with the patient lying on his side and with the X-ray beam centered horizontally provide an improved viewing of small basal pleural effusions and the mobility of mediastinum. An X-ray technique of high quality is needed to obtain important parameters for the diagnosis. Analysis of the X-ray picture must be carried out systemetically. Applied knowledge of clinical data raises the number of correct-positive and incorrect-positive observations. Repeated analysis by the same observer or group observations leads to an increase in the reliability of the diagnosis.