Monte Carlo investigations of radiotherapy beams: studies of conventional, stereotactic and unflattened beams

Abstract

Monte Carlo modelling is a useful method of investigating the electron and photon transport in radiotherapy linear accelerators. The probability of interactions of the materials stored in the cross-section library is considered to be theoretically accurate. Calculations made by Monte Carlo techniques have many roles including investigation of unusual situations where measurements are difficult and as a problem solver. The predictions made by a validated model can be used to confirm an assumption or prove a hypothesis. This study is aimed to investigate the performance of the DOSI detector, a prototype detector which is position sensitive with submillimeter resolution. This solid-state detector is made of p-type diode has silicon material as its volume element. Work from other authors has shown that other silicon detectors overestimate the dose as field size and depth increase. To overcome this, a mechanism for correction has to be determined. For this reason, this investigation compares experimental data and calculated results using Monte Carlo method at 6 MV photon energy from a Varian linear accelerator. A small degree of perturbation has been found from this study, and work on improvement of the dose measurements has been carried out. Results have been presented and suggestion for a better dose meter is discussed.