@misc{oai:repo.qst.go.jp:00076826,
 author = {Matsufuji, Naruhiro and Matsufuji, Naruhiro},
 month = {Sep},
 note = {(Introduction)
As the best use of the Bragg curve nature, hypofractionated ion-beam therapy has been promoted on various tumor site. In carbon-ion therapy for prostate cancer treatment at the Heavy Ion Medical Accelerator in Chiba (HIMAC), radical hypofractionation has been performed by selectively reducing the urethral dose located at the center of the prostate tumor. It is needed there to establish an in-vivo dosimeter to confirm if the dose to urethra is surely reduced as planned during the therapeutic irradiation. This study investigated a response of a miniature sphere diode as a candidate for the in-vivo dosimeter for therapeutic carbon-ion beam.
(Material and Methods)
Sphere diode of 1.2 and 1.8mm in diameter made by Sphelar Power Co., Ltd. (Kyoto, Japan) was tested. The measurement was carried out at the therapeutic port of HIMAC with pristine 290 MeV/n of carbon beam as well as therapeutic 350 MeV/n spread-out Bragg peak (SOBP) beams. Output current from the diode during the irradiation was measured with an electrometer as integral charge. A pinpoint ionization chamber was also used for the sake of comparison.
(Result and Discussion)
The spherical geometry of silicon caused slight broadening or pristine Bragg peak of the carbon-ion beam, however, for SOBP beam it showed superior dosimetric response free from LET dependency as almost comparable as those measured with an ionization chamber. The measurement with the smaller diode successfully reproduced the decrease in dose at the middle of the SOBP intentionally designed to simulate the therapeutic irradiation reducing urethral dose. The diode showed decrease in sensitivity of about 1% / Gy as a function of integral dose, however, the output linearity on dose and subtle incident angular dependence together with the smallness and safeness make the silicon diode as a good candidate for the in-vivo dosimeter in ion-beam therapy., ＂RESPONSE OF A MINIATURE SPHERICAL DIODE AS A DOSIMETER FOR THERAPEUTIC CARBON-ION BEAM＂にて発表を行う},
 title = {24th International Conference on Medical Physics 発表},
 year = {2019}
}