@article{oai:repo.qst.go.jp:00045073,
 author = {Inaniwa, Taku and Kohno, Toshiyuki and Tomitani, Takehiro and Satou, Shinji and 稲庭 拓 and 河野 俊之 and 富谷 武浩 and 佐藤 眞二},
 issue = {3},
 journal = {Physics in Medicine and Biology},
 month = {Jan},
 note = {In order to effectively utilize the prominent properties of heavy ions in radiotherapy, it is important to evaluate both the position of the field irradiated
with incident ions and the absorbed dose distribution in a patient's body. One of
the methods for this purpose is the utilization of the positron emitters produced
through the projectile fragmentation reactions of stable heavy ions with target
nuclei. In heavy-ion therapy, spread-out Bragg peak (SOBP) beams are used to achieve uniform biological dose distributions in the whole tumor volume.
Therefore, in this study, we designed SOBP beams of 30 and 50 mm waterequivalent
length (mmWEL)in width for 12Cand 16O, and carried out irradiation experiments using them. Water, polyethylene and polymethyl methacrylate were selected as targets to simulate a human body. Pairs of annihilation gamma rays were detected by means of a limited-angle positron camera for 500 s, and annihilation gamma-ray distributions were obtained. The maximum likelihood estimation (MLE) method was applied to the detected distributions for evaluating the positions of the distal and proximal edges of the SOBP in a target. The differences between the positions evaluated with the MLE method and those derived from the measured dose distributions were less than 1.7 mm and 2.5 mm for the distal and the proximal edge, respectively, in all irradiation conditions. When the positions of both edges are determined with the MLE method, the most probable shape of the dose distribution in a target can be estimated simultaneously. The close agreement between the estimated and the measured distributions implied that the shape of the dose distribution in an irradiated target could be evaluated from the detected annihilation gamma-ray distribution.},
 pages = {529--542},
 title = {Monitoring the irradiation field of 12C and 16O SOBP beams using positron emitters produced through projectile fragmentation reactions},
 volume = {53},
 year = {2008}
}