title: Spatial fragment distribution from a therapeutic pencil-like carbon beam in water.
abstract: The latest heavy ion therapy tends to require information about the spatial distribution of the quality of radiation in a patient's body in order to make the best use of any potential advantage of swift heavy ions for the therapeutic treatment of a tumour. The deflection of incident particles is described well by Molière's multiple-scattering theory of primary particles; however, the deflection of projectile fragments is not yet thoroughly understood. This paper reports on our investigation of the spatial distribution of fragments produced from a therapeutic carbon beam through nuclear reactions in thick water. A DeltaE-E counter telescope system, composed of a plastic scintillator, a gas-flow proportional counter and a BGO scintillator, was rotated around a water target in order to measure the spatial distribution of the radiation quality. The results revealed that the observed deflection of fragment particles exceeded the multiple scattering effect estimated by Molière's theory. However, the difference can be sufficiently accounted for by considering one term involved in the multiple-scattering formula; this term corresponds to a lateral 'kick' at the point of production of the fragment. This kick is successfully explained as a transfer of the intra-nucleus Fermi momentum of a projectile to the fragment; the extent of the kick obeys the expectation derived from the Goldhaber model.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 263-8555 Chiba, Japan. matufuji@nirs.go.jp
authors.forename: Naruhiro
authors.initials: N
authors.lastname: Matsufuji
authors.forename: Masataka
authors.initials: M
authors.lastname: Komori
authors.forename: Hitomi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Kengo
authors.initials: K
authors.lastname: Akiu
authors.forename: Masako
authors.initials: M
authors.lastname: Ogawa
authors.forename: Akifumi
authors.initials: A
authors.lastname: Fukumura
authors.forename: Eriko
authors.initials: E
authors.lastname: Urakabe
authors.forename: Taku
authors.initials: T
authors.lastname: Inaniwa
authors.forename: Teiji
authors.initials: T
authors.lastname: Nishio
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kohno
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Kanai
mesh_terms: D002244:Carbon; D063193:Heavy Ion Radiotherapy; D020450:Heavy Ions; D008962:Models, Theoretical; D016011:Normal Distribution; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D014867:Water
chemical_list: D014867:Water; D002244:Carbon