title: Modeling of beam customization devices in the pencil-beam splitting algorithm for heavy charged particle radiotherapy.
abstract: A broad-beam-delivery system for radiotherapy with protons or ions often employs multiple collimators and a range-compensating filter, which offer complex and potentially useful beam customization. It is however difficult for conventional pencil-beam algorithms to deal with fine structures of these devices due to beam-size growth during transport. This study aims to avoid the difficulty with a novel computational model. The pencil beams are initially defined at the range-compensating filter with angular-acceptance correction for upstream collimation followed by stopping and scattering. They are individually transported with possible splitting near the aperture edge of a downstream collimator to form a sharp field edge. The dose distribution for a carbon-ion beam was calculated and compared with existing experimental data. The penumbra sizes of various collimator edges agreed between them to a submillimeter level. This beam-customization model will be used in the greater framework of the pencil-beam splitting algorithm for accurate and efficient patient dose calculation.
authors.affiliation: Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan. nkanemat@nirs.go.jp
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kanematsu
mesh_terms: D000465:Algorithms; D063193:Heavy Ion Radiotherapy; D006801:Humans; D008962:Models, Theoretical; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D020266:Radiotherapy, Conformal / Q000295:instrumentation*