Electron transport using neutral particle transport codes.

Abstract

Success of electron beam therapy depends on the ability to deliver a prescribed radiation dose to a tumorous region. ETRAN, a Monte Carlo electron transport code is the most widely used tool for prediction of electron interactions with matter. However, ETRAN results vary by as much as 15% from measured values. The objective of this research is to produce an alternative to ETRAN by applying radiation transport techniques familiar to nuclear engineers. Two computer codes for neutral particle transport have been used. One is a discrete ordinates code ANISN which offers a different approach from ETRAN. The other is a Monte Carlo code MORSE-E which has the capability to model the geometric complexities that occur in measurements. A group-skipping model developed in this work for the preparation of ANISN format electron transport cross sections has been used in calculations by ANISN and MORSE-E.

For the case of a 10 MeV electron beam incident on a water phantom, the energy deposition distribution predicted by ANISN is indistinguishable from that calculated by MORSE-E. The ANISN/MORSE-E results show better agreement with the measured depth dose data than ETRAN calculations. Two-dimensional irradiation geometry calculations by the use of MORSE-E are performed to predict the central-axis depth dose distribution with various sizes of beam field and compared to measured values. Other types of problems which have been solved by ANISN/MORSE-E are: transmitted electron energy/angular distributions in water, aluminum and gold; charge deposition distribution in a water phantom. The calculated results are compared with ETRAN predictions and with available experimental results.