@article{oai:repo.qst.go.jp:00048434,
 author = {Kumagai, Motoki and Hara, Ryusuke and Mori, Shinichiro and Yanagi, Takeshi and Asakura, Hiroshi and Kishimoto, Riwa and Katou, Hirotoshi and Yamada, Shigeru and Kandatsu, Susumu and Kamada, Tadashi and 熊谷 始紀 and 原 竜介 and 森 慎一郎 and 柳 剛 and 浅倉 裕史 and 岸本 理和 and 加藤 博敏 and 山田 滋 and 神立 進 and 鎌田 正},
 issue = {4},
 journal = {International Journal of Radiation Oncology Biology Physics},
 month = {Mar},
 note = {Purpose: We assessed carbon ion beam dose variation due to bowel gas movement in pancreatic radiotherapy.
Material and Methods: A total of 10 pancreatic cancer inpatients were subject to diagnostic contrast-enhanced dynamic helical CT examination under breath-holding conditions, which included multiple-phase dynamic CT with arterial, venous and delayed phases. The time increments of the arterial-venous and arterial-delayed phases were 35 and 145 s, respectively. A compensating bolus was designed to cover the target obtained at the arterial phase. Carbon ion dose distribution was calculated by applying the bolus to the CT data sets at the other two phases.
Results: Dose conformation to the clinical target volume (CTV) was degraded by beam overshoot/undershoot due to bowel gas movement. The D95 for CTV was degraded from 97.4% (range: 97.1% - 98.1%) of the prescribed dose to 93.1% (range: 85.4% - 97.8%) at 145 s. Excessive dosing to normal tissues varied among tissues, and was for example 12.0 GyE/12.9 GyE (0s/ 145s) for the cord and 38.5 GyE/39.6 GyE (0s/145s) for the duodenum. The magnitude of beam overshoot/undershoot was particularly exacerbated from the anterior and left directions.
Conclusions: Bowel gas movement causes dosimetric variation to the target during treatment for radiotherapy. The effect of bowel gas movement varies with beam angle, with greatest influence on the AP and LR beams.},
 pages = {1276--1281},
 title = {Impact of Intrafractional Bowel Gas Movement on Carbon Ion Beam Dose Distribution in Pancreatic Radiotherapy},
 volume = {73},
 year = {2009}
}