@misc{oai:repo.qst.go.jp:00068149,
 author = {Urakabe, Eriko and Kanai, Tatsuaki and Kanazawa, Mitsutaka and Kitagawa, Atsushi and Tomitani, Takehiro and Suda, Mitsuru and Satou, Shinji and Noda, Kouji and Furukawa, Takuji and Mizuno, Hideyuki and Iseki, Yasushi and Inaniwa, Taku and 新谷 恵理子 and 金井 達明 and 金澤 光隆 and 北川 敦志 and 富谷 武浩 and 須田 充 and 佐藤 眞二 and 野田 耕司 and 古川 卓司 and 水野 秀之 and 井関 康 and 稲庭 拓},
 month = {Oct},
 note = {A scheme for spot scanning using 11C beams has been developed in order to form and verify a three-dimensionally conformal irradiation field for heavy-ion radiotherapy. With use of positron emitting 11C beams, the verification of therapeutic irradiation can be directly accomplished by observing annihilation-pair gamma rays from the stopping point in the patient. One of the features of 11C beams is the large number of the gamma rays observed at the range of the incident beam. The half-life of 11C is 20.39 min, which is appropriate for measurements using offline positron emission tomography (PET). 11C produced by a projectile-fragmentation process, however, has considerably different characteristics compared with those of the primary beam: a) low yield (less than 1% of the primary beam); b) wide momentum spread (2%); c) large beam size due to its large emittance (~ 40 pi mm mrad).
We have to compromise the yield and the momentum spread keeping treatment planning in mind. Its low yield motivated us the use of spot scanning method, which is associated with technical difficulties. The spot beam is scanned stepwise over the tumor region by a horizontal and vertical scanning magnets and the range shifter made by PMMA plates. The beam delivery is stopped just after the prescribed dose is reached. For the precise dose management, the fast beam cut-off method is investigated and achieved a cut-off time of around 0.05 ms. During the transition time from one spot to the next one, the position and the width of each spot beam is verified. By selecting the momentum spread of a 11C beam, we could considerably decrease the distal falloff of the irradiation field, thus conserving the beam quality.  
To estimate and optimize the dose distribution in the irradiation field, it is essential to evaluate precisely the dose distribution of spot beams. It is pointed out that the chromatic aberration and the dispersion should be taken into account to calculate the dose distribution of 11C beams. A concave-shaped field in PMMA phantom was optimized and experimentally evaluated.
In this conference, a scheme for spot scanning that uses the above-described features of 11C beams will be reported. In this study, we focus mainly on the dose estimation of 11C spot beams., 9th Workshop on Heavy Charged Particles in Biology and Medicine 2003 and 3rd Meeting of the European Network for Light Ion Hadron Therapy},
 title = {SPOT SCANNING USING 11C BEAMS FOR HEAVY-ION RADIOTHERAPY},
 year = {2003}
}