カワムラ　ヒデマサ   KAWAMURA Hidemasa   河村　英将    所属   埼玉医科大学  医学部 総合医療センター　放射線科(画像診断・核医学科、放射線腫瘍科)    職種   教授
論文種別	学術雑誌(原著)
言語種別	英語
査読の有無	査読あり
表題	The impact of the grid size on tomotherapy for prostate cancer
掲載誌名	正式名：Journal of Medical Physics ISSNコード：1998-3913
出版社	Medknow Publications
巻・号・頁	42(3),144-150頁
著者・共著者	Motohiro Kawashima,Hidemasa Kawamura,Masahiro Onishi,Yosuke Takakusagi,Noriyuki Okonogi,Atsushi Okazaki,Tetsuo Sekihara,Yoshitaka Ando,Takashi Nakano
発行年月	2017/07/01
概要	Discretization errors due to the digitization of computed tomography images and the calculation grid are a significant issue in radiation therapy. Such errors have been quantitatively reported for a fixed multifield intensity-modulated radiation therapy using traditional linear accelerators. The aim of this study is to quantify the influence of the calculation grid size on the dose distribution in TomoTherapy. This study used ten treatment plans for prostate cancer. The final dose calculation was performed with 'fine' (2.73 mm) and 'normal' (5.46 mm) grid sizes. The dose distributions were compared from different points of view: the dose-volume histogram (DVH) parameters for planning target volume (PTV) and organ at risk (OAR), the various indices, and dose differences. The DVH parameters were used Dmax, D2%, D2cc, Dmean, D95%, D98%, and Dmin for PTV and Dmax, D2%, and D2cc for OARs. The various indices used were homogeneity index and equivalent uniform dose for plan evaluation. Almost all of DVH parameters for the 'fine' calculations tended to be higher than those for the 'normal' calculations. The largest difference of DVH parameters for PTV was Dmax and that for OARs was rectal D2cc. The mean difference of Dmax was 3.5%, and the rectal D2cc was increased up to 6% at the maximum and 2.9% on average. The mean difference of D95% for PTV was the smallest among the differences of the other DVH parameters. For each index, whether there was a significant difference between the two grid sizes was determined through a paired t-test. There were significant differences for most of the indices. The dose difference between the 'fine' and 'normal' calculations was evaluated. Some points around high-dose regions had differences exceeding 5% of the prescription dose. The influence of the calculation grid size in TomoTherapy is smaller than traditional linear accelerators. However, there was a significant difference. We recommend calculating the final dose using the 'fine' grid size.
DOI	10.4103/jmp.JMP_123_16
PMID	28974860