Study of te evolution of the GEANT4 electrons transport algorithm to applications in radiotherapy

In this work a bibliographic review was made about the GEANT4 applicability in radiotherapy, and also a study of electrons transport algorithm in order to establish the key points for future works with GEANT4. In papers already published, the GEANT4 version 4.6.1 was considered appropriated for photons simulations in applications of clinic significance in radiotherapy (accuracy ∼ 2%), however to electrons was checked that versions older than 8.3 present problems related to electrons transport algorithm, as size step artifact. The GEANT4 algorithm revision, version 8.3, resulted in substantial improvements of some values calculated in simulations, especially the loss energy per step and the boundary vicinity simulation of electrons, beyond better results stability, compared to versions 8.2. We concluded that electrons transport parameters within the following ranges: dRoverRange<0.3, RangeFactor=0.02, GeomFactor=3 and skin=1 is possible to get results with 1% accuracy to cavities simulations, although occur differences between simulated and theoretical doses, indicating that others parameters and the dose shift should be better evaluated. (author)