Calculation of electron dose distribution for radiotherapy treatment planning

Abstract

It is difficult to obtain electron dose distributions in a phantom by calculation. A formula was derived from the age diffusion equation, which includes terms for the electron dose, the distance from the central axis of the field, the depth in the phantom, the width of the field on the surface, the diffusion coefficient of the medium, the extrapolated electron range and an 'age' parameter which increases as the electron energy is degraded in the medium. This formula is able to generate a spatial electron dose distribution with good approximation to experimental values given only the incident electron energy and field size.