title: Treatment planning for the layer-stacking irradiation system for three-dimensional conformal heavy-ion radiotherapy.
abstract: We have upgraded a heavy-ion radiotherapy treatment-planning system to adapt for the layer-stacking irradiation method, which is to conform a variable spread-out Bragg peak to a target volume by means of dynamic control of the conventional beam-modifying devices. The biophysical model, the beam-setup logic, and the dose-calculation algorithm implemented for the layer-stacking method are described and the expected clinical usability is discussed. The layer-stacking method was integrated in perfect accordance with the ongoing conventional treatments so that the established protocols, which are the clinically optimized dose fractionation schemes, will still be valid. On the other hand, a simulation study indicated a substantial improvement of dose distribution with the layer-stacking method though the significance may depend on the size, shape, and location of the tumor. The completed treatment system will provide an option for improved conformal radiotherapy without interfering with the conventional method and we expect a gradual expansion of the clinical cases applicable to the layer-stacking method.
authors.affiliation: Department of Medical Physics, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-Ku, Chiba 263-8555, Japan. nkanemat@nirs.go.jp
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kanematsu
authors.forename: Masahiro
authors.initials: M
authors.lastname: Endo
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Futami
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Kanai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asakura
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Oka
authors.forename: Ken
authors.initials: K
authors.lastname: Yusa
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D003198:Computer Simulation; D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D063193:Heavy Ion Radiotherapy; D006801:Humans; D011878:Radiotherapy / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D014057:Tomography, X-Ray Computed