tomography

(also body section roentgenography or sectional radiography), a technique of roentgenological study that is used to produce a photograph of a layer lying at a specific depth in the object under study.

Ordinary roentgenography results in the production on film of an overall image, from which it is not always possible to determine the true shape and size of a formation or the depth at which it lies. The production of a roentgenogram of a single layer is based on the movement of two of the three components (the X-ray tube, the X-ray film, and the object of study). In the most common technique, the patient is motionless, and the X-ray tube and film magazine move around him in opposite directions. The use of tomography makes possible the study of the trachea, the bronchi, and the blood vessels and the detection of infiltrates and cavities of the lungs, calculi in the kidney, gallbladder, and bile ducts, and tumors in the adrenals and urinary system. The combined use of X-ray contrast media and tomography (sectional bronchography, urography, and so on) is highly effective.