title: Monte Carlo based phase-space evolution for electron dose calculation.
abstract: A system of computer codes based on phase-space evolution is developed and applied to low energy therapeutic electron beams. Monte Carlo (EGS4) is used to pre-calculate the electron transport and dose deposition in a 0.5 cm width cubic voxel. Dose calculations at larger scales are computed from the pre-calculated data using phase-space evolution. This approach has the theoretical accuracy of Monte Carlo with potentially significant speed gains resulting from the pre-calculation. This study demonstrates the accuracy of this technique while providing a preliminary assessment of the calculation time. For a 4.3 MeV electron beam in water with a 0.5 cm thick slab of either water (homogeneous), air, or aluminum at 1 cm depth, we observe differences relative to Monte Carlo of less than 3% along the central axis for a pencil-beam. For a 3.5 cm x 3.5 cm field we observe a maximum difference on the central axis of 4% in the build-up region and less than 0.1 cm in the fall-off region for all three phantoms. Calculation times are disappointing; however, there is high potential for their reduction to values comparable to or better than condensed history Monte Carlo while retaining clinically acceptable accuracy.
authors.affiliation: Toronto-Sunnybrook Regional Cancer Centre, Ontario, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Scora
authors.forename: B A
authors.initials: BA
authors.lastname: Faddegon
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D004583:Electrons / Q000627:therapeutic use*; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D013679:Technology, Radiologic