Fast electron beam simulation and dose calculation in radiotherapy

Abstract

A flexible multiple source model capable of fast reconstruction of clinical electron beams is presented in this paper. A source model considers multiple virtual sources emulating the effect of the accelerator head components. A reference configuration ( 10 MeV and 10×10 cm 2 field size) for a Siemens KD2 linear accelerator was simulated in detail using the GEANT3 Monte Carlo code. Our model allows the reconstruction of other electron energies and field sizes, as well as other beam configurations of similar accelerators, using only the reference beam data. Electron dose calculations with the reconstructed beams were performed in a water phantom and compared with experimental data. An agreement of 1–2%/1– 2 mm was obtained, comparable to the accuracy of full Monte Carlo accelerator simulation. The source model reduces accelerator simulation CPU time by a factor of 7500 relative to full Monte Carlo approaches. The developed model was then interfaced to DPM, a fast radiation transport Monte Carlo code for dose calculation. Dose distributions and dosimetric parameters computed in the presence of air gaps using this procedure agree within 1%/ 1 mm with experimental data. The obtained accuracy corresponds to a significant improvement when compared to the treatment planning system PLATO, currently used in clinical practice. Globally, a two order of magnitude efficiency gain was achieved with respect to the full Monte Carlo approach.