title: Experimental evaluation of validity of simplified Monte Carlo method in proton dose calculations.
abstract: It is important for proton therapy to calculate dose distributions accurately in treatment planning. Dose calculations in the body for treatment planning are converted to dose distributions in water, and the converted calculations are then generally evaluated by the dose measurements in water. In this paper, proton dose calculations were realized for a phantom simulating a clinical heterogeneity. Both dose calculations in the phantom calculated by two dose calculation methods, the range-modulated pencil beam algorithm (RMPBA) and the simplified Monte Carlo (SMC) method, and dose calculations converted to dose distributions in water by the same two methods were verified experimentally through comparison with measured distributions, respectively. For the RMPBA, though the converted calculations in water agreed moderately well with the measured ones, the calculated results in the actual phantom produced large errors. This meant that dose calculations in treatment planning should be evaluated by the dose measurements not in water but in the body with heterogeneity. On the other hand, the results calculated in the phantom, even by the less rigorous SMC method, reproduced the experimental ones well. This finding showed that actual dose distributions in the body should be predicted by the SMC method.
authors.affiliation: Institute of Applied Physics, University of Tsukuba, Tsukuba 305-8573, Japan. r_kohno@nirs.go.jp
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kohno
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Takada
authors.forename: Takeji
authors.initials: T
authors.lastname: Sakae
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Terunuma
authors.forename: Keiji
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nohtomi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Matsuda
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy; D019047:Phantoms, Imaging / Q000706:statistics & numerical data; D061766:Proton Therapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data*; D011882:Radiotherapy, High-Energy / Q000706:statistics & numerical data; D014867:Water
chemical_list: D014867:Water