@article{oai:repo.qst.go.jp:00046496,
 author = {Hara, Yousuke and Takada, Yoshihisa and Hotta, Kenji and Tansho, Ryohei and Nihei, Tetsuya and Suzuki, Yojiro and Himukai, Takeshi and Matsufuji, Naruhiro and et.al and 原 洋介 and 高田 義久 and 堀田 健二 and 丹正 亮平 and 二瓶 哲哉 and 鈴木 庸次郎 and 日向 猛 and 松藤 成弘},
 issue = {6},
 journal = {Physics in Medicine and Biology},
 month = {May},
 note = {We have developed a novel designmethod of ridge filters for carbon-ion therapy
using a broad-beam delivery system to improve the flatness of a biologically
effective dose in the spread-out Bragg peak (SOBP). So far, the flatness of the
SOBP is limited to about +-5% for carbon beams since the weight control
of component Bragg curves composing the SOBP is difficult. This difficulty
arises from using a large number of ridge-bar steps (e.g. about 100 for a SOBP
width of 60 mm) required to form the SOBP for the pristine Bragg curve with an
extremely sharp distal falloff. Instead of using a single ridge filter, we introduce
a ripple filter to broaden the Bragg peak so that the number of ridge-bar steps
can be reduced to about 30 for SOBP with of 60mmfor the ridge filter designed
for the broadened Bragg peak. Thus we can manufacture the ridge filter more
accurately and then attain a better flatness of the SOBP due to well-controlled
weights of the component Bragg curves.We placed the ripple filter on the same
frame of the ridge filter and arranged the direction of the ripple-filter-bar array
perpendicular to that of the ridge-filter-bar array. We applied this method to a
290 MeV u-1 carbon-ion beam in Heavy Ion Medical Accelerator in Chiba and
verified the effectiveness by measurements.},
 pages = {1717--1731},
 title = {Improvement of spread-out Bragg peak flatness for a carbon-ion beam by the use of a ridge filter with a ripple filter},
 volume = {57},
 year = {2012}
}