Correction for the angular dependence of a detector in electron and photon beams.

Abstract

Based on experimentally obtained angular response functions a simple analytic function has been found which can be accurately fitted to such data. Using this function formulas are derived for the variation of the detector response as the angular distribution of the electrons are changing with depth in a phantom both in electron and photon beams. The formulas show that for a flat liquid ionization chamber, a response variation of 2 to 4 per cent is normally obtained in the build-up region of electron and photon beams whereas the response is practically constant beyond dose maximum.