[en] Recently, the abscopal effect has been extensively investigated. We reported that both X-ray and carbon ion irradiation combined with the dual immune checkpoint blockade (Anti PD-L1 (P1) and anti-CTLA-4 (C4) antibodies) induced the abscopal effect with high probability in murine osteosarcoma model. We have also revealed that even single immune checkpoint blockade, C4, with carbon ion irradiation at lower dose was still effective for both local and abscopal sites for a mouse osteosarcoma model. In this year, we examined the combined effect of carbon ion irradiation at various dose and fractionation with C4 therapy on local and abscopal effects and immune microenvironment changes in a pancreas ductal carcinoma (PDAC) mouse model. Our results revealed that addition of high dose local carbon ion irradiation to C4 enhanced local and abscopal responses with increased cytotoxic T cells and reduced regulatory T cells in both irradiated and abscopal tumors, regardless of fractionation in the carbon ion beam delivery. Furthermore, unlike to photon beam, even lower dose of carbon ion irradiation with C4 seems still effective to enhance abscopal response. We will further investigate the details in PDAC mouse model. (author)

[en] A series of FT-IR spectrometric studies has been made on modified structure along ion tracks in PET, PC, PI and PADC. Systematic response studies were also performed on them as etched track detectors, paying a special attention on each detection thresholds. It has been confirmed that the three way junctions in PADC polymeric network are radiation tolerance, which have each methine group. (author)

[en] Hadron therapy is known as one of the most efficient radiation therapies for cancers. For daily quality assurance (QA) measurements in hadron (mostly proton and carbon) radiotherapy, a dosimetry system that has a two-dimensional effective area, high spatial resolution, and linear response-to-dose is required. We demonstrate the dose imaging performance of a novel digital dose imager using carbon ion beams for hadron therapy. The dose imager is based on a gaseous detector, a well-type glass gas electron multiplier. The imager is successfully operated in a hadron therapy facility with clinical intensity beams for radiotherapy. It features a high spatial resolution of less than 1 mm and an almost linear dose-response relationship with no saturation and very low linear-energy-transfer (LET) dependence. However, experimental results show small disagreement in fragment region, and spread out Bragg peak (SOBP) beam measurement. We assumed that this is due to the effect of secondary particles produced by the cathode material. Therefore, we have experimentally investigated the effect of the cathode material on various cathode materials. In this talk, we will discuss the evaluation results of using aluminum, copper, film, and graphite materials as cathode materials respectively. (author)

[en] In order to study the reaction mechanism and the potential acting through a fragmentation process at intermediate energies, the transverse momentum (P_T) distribution of reaction products was measured by using a secondary beam course, SB2, at HIMAC. This year, P_T distribution of fragments, produced through one-proton removal reaction with ⁴⁰Ar beam and targets (C, Nb, Tb, and Au) at E = 200 MeV/nucleon, has been observed as its angular distribution. A deflection angle was obtained by analyzing angular distributions observed at E = 100, 200, and 290 MeV/nucleon. The trajectory calculation has been carried out to evaluate the deflection angle by considering the Coulomb- and nuclear-potential acting between the projectile and target nuclei. Deflection angle obtained from measurements, which changes according to target and projectile energy, was reproduced by calculated results, successfully. (author)

[en] For the particle detector in high radiation environment, we have developed new semiconductor detectors by the Cu(In,Ga)Se₂ (CIGS) and Gallium Nitride (GaN). The small samples of CIGS and GaN detectors were tested with 400 MeV/n Xe beam at the HIMAC and both successfully detected Xe particle as a single event. For the CIGS detector, the outputs reduced by irradiation of the Xe beam, while it was recovered with the heat annealing at 130℃. (author)

[en] In order to estimate energy deposition by heavy ion irradiation, the concentration of radicals and products formed in alanine-d4 were investigated. Irradiations of Ne-ion (400 MeV/u) and Fe-ion (500 MeV/u) were conducted at the LET values of 31, 115, 150, 200, 260 and 320 eV/nm. The intensity of ESR signal decreased with increasing the LET value. On the contrary, the linewidth of ESR signal became broad and the spin-spin relaxation time became shorter by irradiation at higher LET. (author)

[en] Dose-averaged LET (LETd) is one of the important factors in determining clinical outcomes for carbon-ion radiotherapy. Innovative LET painting (LP) has been developed as a specific type of intensity-modulated carbon-ion radiotherapy. The purpose of this study was to increase minimum LETd for the gross tumor volume (GTV) while maintaining target dose coverages and risk organ dose constraints by the LP treatment plan for head and neck cancer patients in silico study. LP treatment plans were designed with the in-house treatment planning system. For 13 head and neck cancer cases, the target dose coverage and LETd planned from the LP were compared with those planned from conventional plans. The median minimum LETd for the GTV of the conventional plans was 45 keV/um (range 33-52). The median minimum LETd for the GTV of the LP plans was 59 keV/um (range 44-76). The minimum LETds were increased by LP plan (median: 15 keV/um, range: 11-24) while maintaining target dose coverages and risk organ dose constraints in all cases. LP could increase the median minimum LETd up to +15 kev/um for the GTV as compared to the conventional plans. Hereby, we could establish the LP treatment planning procedure for head and neck cancer toward the clinical application of the LP. (author)

[en] Comparison study aims to investigate the differential Coulomb nanoradiator effect (CNR) between proton and Carbon ion due to potent larger Coulomb interaction cross-section with given nanoparticles from heavy ion. In this year, Therapeutic efficacy of CNR effect was supposed to be measured with F98 rat glioma model given BBB crossing and glioma targeting ApoB(a)AuNP sensitized by Carbon beam with a pristine Bragg peak and compared with the results of 100 MeV proton irradiation in range of 1-10 Gy. Although Carbon experiment was not performed due to Covid pandemic, the proton result was published in a Journal. Proton sensitization treated the TME and bulk tumor volume with enhanced therapeutic efficacy by 67-75% compared to that with protons alone. Immunohistochemistry demonstrated efficient treatment of endothelial cell proliferation and migratory tumor cells of invasive microvessels in the TME with saving normal tissues. (author)

[en] This report summarises the progress to date of continuing project 21J146. We report the outcome of a recent baseline study of the response of our proposed in vivo tumour model to standard helium and carbon ion therapy, conducted at HIMAC, as well as several other key results including XFM biodistribution measurements performed at the Australian Synchrotron. (author)

[en] We are developing a small-size dosimeter combining a scintillator element and an optical fiber. In this study, we evaluated various properties of the small-size dosimeter for use in the carbon-ion radiotherapy. Since a scintillator has fast response, there is a possibility to obtain fine time profile of dose in scanning irradiation therapy. For feasibility study of the small-size dosimeter to the scanning irradiation, the measurement of the distribution of carbon beam in water was evaluated. (author)