Fluoroscopy of the chest.

A postero-anterior teleoroentgenogram of the chest is primarily a "scout" film, and diagnosis based solely on such an examination is often little more than guesswork. However, this film serves admirably in detecting most lesions, and aids in determining what additional studies need to be performed. Unless the clinical or roentgen diagnosis is evident, one should then proceed with further roentgen study. As a general rule this should begin with fluoroscopy. A complete chest fluoroscopy can be accomplished within a few minutes if the examiner applies a well-organized approach. For purposes of instructing students and residents, we have divided pulmonary fluoroscopy into five phases which we have designated as Observation, Rotation, Breathing, Ingestion and Tilting. Their first letters spell the word ORBIT, which serves as a mnemonic. 1. Observation. After preliminary fluoroscopy of the entire chest, including the heart, attention is directed to the lesion in question. Its size, shape, homogeneity and margination are closely studied. The presence or absence of pulsation should be noted. However, this is of little significance unless opposite sides of the lesion can be seen simultaneously, since differentiation between transmitted and intrinsic pulsation cannot otherwise be made. Even under those conditions aneurysms cannot be reliably distinguished from tumors, since aneurysms often contain clot which interferes with expansile pulsation, and tumors occasionally surround a vessel and may then appear to pulsate expansively. 2. Rotation. By slightly rotating the patient (10 to 20 degrees) one can quickly establish whether a density lies anteriorly or posteriorly. Storchl utilizes the sternum and spine as reference points. If, on rotation, the lesion moves in the same direction the spine moves, i t is posterior, whereas if i t moves with the sternum i t is anterior in location (Fig. 1). The amount of movement of the lesion indicates how far i t lies from the center of the thorax (the vertical axis on which the patient is rotated). Thus, peripheral lesions shift more with rotation than central ones. Rotation serves to separate a lesion from adjacent structures so that a clearer view of i t is obtained. Obviously, if the lesion can be separated entirely from a superimposed structure by rotation, there is little likelihood that i t is connected with that structure. Rotation is also helpful in differentiating hilar node enlargement from vascular shadows, the nodes remaining rounded while vascular shadows elongate or disappear as the patient is turned. As a lesion comes closer to the fluoroscopic screen, its image appears smaller and sharper. If a density is smaller in the postero-anterior projec-