SIMULATION OF THE UPPER GASTROINTESTINAL FLUOROSCOPIC EXAMINATION FORCALCULATION OF ABSORBED DOSE IN TISSUE

In order to simulate the upper gastrointestinal fluoroscopic examinati on, modifications were made to the Monte Carlo radiation-transport cod e that uses the anthropomorphic, mathematical reference phantoms ADAM and EVA. A set of discrete x-ray field projections of the principal an atomy of clinical interest has been previously defined. This note desc ribes the new features incorporated in the simulations-divergent beams in oblique irradiation geometries, an esophagus and a duodenum, a dou ble contrast medium consisting of a BaSO4-H2O mixture and air in the e sophagus, stomach, and duodenum, and clinically representative beam qu alities. The absorbed doses in tissues per unit entrance exposure (fre e-in-air) computed with the modified code appeared in Department of He alth and Human Services Publication FDA 92-8282, Handbook of Selected Tissue Doses for the Upper Gastrointestinal Fluoroscopic Examination. A minor correction is described for the previously reported results fo r the esophagus.