[9a-Z14-1~12] 2.5 Medical application

[9a-Z14-11] Estimation of Shifts of Therapeutic Carbon-Ion Beams Owing to Cavities in Target by Measuring Prompt X-rays

〇Mitsutaka Yamaguchi¹, Seiichi Yamamoto², Maki Kitano², Yoshiki Kubota³, Makoto Skai³, Takashi Akagi⁴, Yuto Nagao¹, Naoki Kawachi¹ (1.QST Takasaki, 2.Nagoya Univ., 3.Gunma Univ., 4.HIBMC)

Keywords:particle-beam cancer therapy, prompt X-ray, secondary electron bremsstrahlung

A method for estimating the shift of therapeutic carbon-ion beams owing to a cavity in a target was studied and the estimation ability was evaluated by measuring the prompt X-rays (secondary electron bremsstrahlung). A polyethylene target with a square prismatic cavity was irradiated with 241.5 MeV/u carbon-ion beams. A pinhole-type prompt X-ray camera was installed next to the target to obtain beam trajectory images. The cavity thickness was varied from 3.0 cm to 0.0 cm in 0.3 cm increments. Beam trajectory images were obtained by irradiating 7.5×10¹⁰carbon ions. In the image, the gap between the beam trajectory and the cavity was clearly identified in the trajectory. The beam deviation estimated from the images was in good agreement with the actual cavity thickness. It was found that the beam shift due to the cavity in the target could be accurately evaluated with an accuracy of about 0.2 cm.