Volume doses determined by computer from dose-distribution measurements

Paper describes determination of the variation of volume doses in a large size dog phantom with X-irradiation of different energies /70, 100 and 200 keV/ and gamma irradiation /60Co/ used. Skin dose was kept identical in every case. The method used for determination of dose distribution was a combination of film dosimetry and Sievert condenser ionization chanber technique. Film dosimeters were calibrated in each case to eliminate errors due to changes in the composition of radiation spectrum. Measurements were made in planes perpendicular to the direction of radiation at several hundred points. Volume doses for the slices between two of these planes were calculated from the data. Calculations, made by reiterated application of the Mayneord formula, were computerized. Authors show, that i. volume dose increases with increasing quantum energy of the radiation ii. using the same irradiation the volume doses significantly drop along the long axis of the phantom iii. this drop is caused mainly by the decrease of body cross-section. (B.A.)