The influence of beam parameters on percentage depth dose in electron arc therapy

The dependence of rotational or arc electron beam percentage depth doses on the depth of isocenter d i and nominal beam field width w is presented. A characteristic angle β, which uniquely depends on w and d i , is defined and the dependence of the radial percentage depth doses on angle β discussed. It is shown that the characteristic angle β concept can be used in clinical situations to predict the shape of the percentage depth dose curve when w and d i are known, or, more importantly, it can be used to determine the appropriate w when d i and the percentage depth dose characteristics are known.