Calculation of Equivalent Square Fields in Radiation Therapy by an Improved Vadash Correction Factor for Collimator Exchange Effects

Abstract

Background and objectives: To determine the head scatter factor, a formalism presented by Vadash and Bjärngard<br />has been employed to assess collimator exchange effects. The aim of this study was to determine the best Vadash<br />correction factor (A) by introducing a new method based on the output factor measured in air for different square and<br />rectangular fields. Materials and Methods: A new simple mathematical method based on selection of the best dosimetric<br />data was proposed to obtain the A value for Vadash to predict the equivalent square field size. Measurements were<br />performed with a Farmer c