Peculiarities of a collimated beam of radiation gamma-therapeutic unit

It has been shown that a generally accepted formula for determining the width of geometric penumbra of the collimated beam of radiation was not a universal one. New dependencies have been proposed, taking into account constructive peculiarities of gamma-therapeutic unit: diagram modification, height of the active part and the unit size of irradiation field. With the help of autoisodosograph the authors studied the influence of three modifications of the regulated diaphragms, differing in orientation of the collimation canal surfaces on the slope of the dose decrease on the irradiation field border. The results of measurements confirmed that by the given criterion the choice of the diaphragm of the first modification for the homemade remote static and rotation apparatus has been correct