title: Preliminary calculation of RBE-weighted dose distribution for cerebral radionecrosis in carbon-ion treatment planning.
abstract: Cerebral radionecrosis is a significant side effect in radiotherapy for brain cancer. The purpose of this study is to calculate the relative biological effectiveness (RBE) of carbon-ion beams on brain cells and to show RBE-weighted dose distributions for cerebral radionecrosis speculation in a carbon-ion treatment planning system. The RBE value of the radionecrosis for the carbon-ion beam is calculated by the modified microdosimetric kinetic model on the assumption of a typical clinical α/β ratio of 2 Gy for cerebral radionecrosis in X-rays. This calculation method for the RBE-weighted dose is built into the treatment planning system for the carbon-ion radiotherapy. The RBE-weighted dose distributions are calculated on computed tomography (CT) images of four patients who had been treated by carbon-ion radiotherapy for astrocytoma (WHO grade 2) and who suffered from necrosis around the target areas. The necrotic areas were detected by brain scans via magnetic resonance imaging (MRI) after the treatment irradiation. The detected necrotic areas are easily found near high RBE-weighted dose regions. The visual comparison between the RBE-weighted dose distribution and the necrosis region indicates that the RBE-weighted dose distribution will be helpful information for the prediction of radionecrosis areas after carbon-ion radiotherapy.
authors.affiliation: Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba-shi, Chiba 263-8555, Japan. y.kase@scchr.jp
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kase
authors.forename: Takeshi
authors.initials: T
authors.lastname: Himukai
authors.forename: Ai
authors.initials: A
authors.lastname: Nagano
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tameshige
authors.forename: Shinichi
authors.initials: S
authors.lastname: Minohara
authors.forename: Naruhiro
authors.initials: N
authors.lastname: Matsufuji
authors.forename: Junetsu
authors.initials: J
authors.lastname: Mizoe
authors.forename: Piero
authors.initials: P
authors.lastname: Fossati
authors.forename: Azusa
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Tatsuaki
authors.initials: T
authors.lastname: Kanai
mesh_terms: D001930:Brain Injuries / Q000209:etiology / Q000473:pathology; D001932:Brain Neoplasms / Q000532:radiotherapy*; D002244:Carbon / Q000627:therapeutic use; D063193:Heavy Ion Radiotherapy; D006801:Humans; D009336:Necrosis; D011832:Radiation Injuries / Q000209:etiology / Q000473:pathology; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012062:Relative Biological Effectiveness
chemical_list: D002244:Carbon