High-Voltage Technic in the Diagnosis of Polypoid Growths of the Colon

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Abstract
All radiologists realize the limitations of a fully opaque barium enema for the demonstration of polypoid growths of the colon. This realization has stimulated the use of double-contrast studies (Fischer, Weber), spot films with compression, the study of the mucosal appearance after evacuation (Berg, Forssell) and the use of semitransparent media (Ledoux-Lebard and Garcia-Calderon). All these technics involve a considerable amount of labor on the part of the patient and of the doctor, and each of them has its own inherent limitations. A double-contrast study of the colon is indeed a beautiful and brilliant procedure when successful, but too often the heavy barium mixture collects in pools which show no double contrast or dries in scales when the water has been absorbed too thoroughly by the thirsty mucosa of the colon. The mucosal study after evacuation of the enema can be confusing. One should, of course, be familiar with the mucosal pattern of the colon, but one must realize how strange it would seem if, when looking for an ink spot on a piece of cloth, we should wrinkle the cloth instead of stretching it flat. Compression films are useful, but the colon is a long organ and one cannot study all of it by this means; the flexures, the rectum, and the sigmoid cannot be compressed because of their deep location. Semitransparent media were used by Ledoux-Lebard and Garcia-Calderon because polypoid growths are shown as radiolucent defects on the films. These media, however, are expensive (one must use thorium because thin barium suspensions are deposited too rapidly) and give very poor fluoroscopic images. A semi-transparent study must be supplemented by a second enema of fully opaque barium for the fluoroscopy. In 1936, Rigler and Eriksen advocated the use of over-exposed films for the demonstration of polypoid growths of the stomach. Independently, and a few months later, I began to study the possibilities of the “over-exposure” or high-voltage technic in the examination of the colon. This technic is based on the observation that radiographic opacity changes with the voltage employed. Thus, a barium mixture which is fully opaque at fluoroscopy can be made more and more transparent by increasing the voltage for radiography. This means that the depth of the colon, as well as its surface, can be made visible, just as we see the trabeculation of bone or transparent stones in the gallbladder. The first thing to be done was to find the minimum amount of barium necessary in a susqension which would be fully opaque at fluoroscopy. One part of barium powder to four parts of water by volume gave a mixture which was fluoroscopically opaque. The radiographic voltage necessary to penetrate this mixture is well within the range of most modern machines. We use 100 kv., 300 ma., 1/8 to 3/8 sec., Bucky, 36 inches distance, par speed screen. With these factors, we can see one loop of the colon through another loop, and radiolucent areas become readily visible.

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