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GRID irradiation of mouse intestinal tract using scanned carbon-ion beams
No full textBackground and aims:Spatial fractionated (GRID) radiotherapy is expected to induce stronger immune responses by administering higher doses to a tumor while sparing the surrounding normal tissues. However, in vivo experimental data for GRID irradiation, especially for serial organs, are limited. Heavy ions exhibit small lateral scattering, potentially realizing GRID irradiation with small beam sizes without any physical collimator. This study evaluated the response of mouse intestinal tract to GRID irradiation using scanned carbon-ion beams.Methods:Monoenergetic 430-MeV/u scanned carbon-ion beams were irradiated to the abdominal region of 7–8 weeks old female C3H/He mice. The GRID irradiation field consisted of seven pencil beams, forming a hexagonal close-packed structure. The pencil beam size was 1.8 mm at 1σ (4.2 mm at FWHM), and the center-to-center distance was 10 mm. When “valley” was defined at the center position of the two and three peaks, the peak-to-valley ratios were 24 and 57, respectively. For the comparison, 20×20-mm2 conventional uniform (CONV) irradiation was performed. The primary endpoint was acute intestinal death within 15 days after irradiation; 3–9 mice were assigned for various dose levels (GRID peak: 13–141 Gy, CONV: 12–17 Gy). The body weights were measured at least three times per week for 30 days.Results:Acute intestinal death occurred between 6–10 days after irradiation. Median lethal doses within 15 days after irradiation were 51.8 Gy at GRID peak and 13.7 Gy for CONV irradiation, respectively; however, field-averaged dose was only 13% higher for the GRID irradiation. Recovery from weight loss was slower for survivors of lethal GRID irradiation (peak dose: 47 Gy) than those of lethal CONV irradiation (dose: 14 Gy). Mice receiving GRID peak dose of 14 Gy did not show weight loss. Between 24–30 days after irradiation, five mice died for GRID irradiation (peak dose: 39–94 Gy) and one mouse died for CONV irradiation (dose: 13 Gy).Conclusions:GRID irradiation using scanned carbon-ion beams allowed higher maximum dose to mouse intestinal tract. However, local radiation injury was indicated to be severe in lethal GRID irradiation. Results of long-term follow-up and pathological analysis will also be presented.PTCOG 63conference presentatio
Development of a beam delivery time (BDT) model for dynamic ion arc therapy using helium, carbon, oxygen and neon ions
No full textAims: Significant reductions in treatment delivery times for ion therapy were made possible for synchrotron-based systems through the development of fast raster-scanning and multi-energy extraction (MEE) operation. Nonetheless, the temporal structure of beam delivery, beam delivery time (BDT) and beam delivery efficiency (BDE) remain unexplored or insufficiently characterized. The aim of this study is to perform a comprehensive analysis of the temporal structure of beam delivery for raster-scanned helium-, carbon-, oxygen-, and neon-ion beams. A machine-specific BDT model was established towards novel delivery strategies like ion arc therapy.Material & methods: The temporal structure of beam delivery was analyzed and modeled, based on parameterization of beam-on (ton) and beam-off (toff) times per energy layer (EL), such that the total BDT (TBD) equals ∑(ton+toff) of all ELs. ton was simply predicted, considering beam intensity and number of particles per EL, while toff was modeled by the number of particles in the synchrotron, time duration for a new synchrotron cycle, and time durations to reduce or maintain the beam energy. Model validation was performed by comparing predicted and measured TBD for clinical treatments.Results: Model predictions for ton were within <0.1% of measurements, while deviations in toff predictions versus measurements varied, mainly due to uncertainties in time durations to maintain the energy and reduce the energy at low energy region. Average measured TBD was 96 s and model prediction errors were within ~3.8(±4.5)% (fig.1a), demonstrating acceptable agreement across patient cohorts and ion species. The largest deviations occurred for H&N cases which commonly use low-energy beams. BDE (∑ton/TBD) was ~20-40% (fig.1b), signifying potential for further BDT optimization.Conclusions: This work developed and validated the first BDT model for helium-, carbon-, oxygen-, and neon-ion therapy. The model will be used for machine performance evaluation, BDE optimization, and optimization of ion arc therapy.IUPESM2025conference presentatio
A Novel Cancer Treatment Using Radiotherapy-Induced Autoantibodies: Overcoming the Limitations of Dendritic Cell Vaccine Therapy
No full textRadiotherapy (RT) not only destroys tumor cells but also induces systemic antitumor immunity. These effects have motivated combining RT with immunotherapies to control local and distant disease. Immune checkpoint inhibitors (ICIs) can be effective, but they rely on pre-existing T cell immunity and often fail in poorly immunogenic tumors. As a form of immunotherapy, dendritic cell (DC) vaccine therapy can prime tumor-specific cytotoxic T lymphocytes (CTLs), but its efficacy is limited because injected DCs migrate poorly to draining lymph nodes, where CTLs are activated.We found that local X-ray irradiation markedly increased serum levels of radiotherapy-induced tumor-binding autoantibodies (TBA) in B16F10-OVA tumor–bearing mice. Based on this finding, we developed a novel approach using these TBA, collected from serum of irradiated mice, to enhance DC vaccine therapy. To our knowledge, this is the first study to utilize radiotherapy-induced autoantibodies for cancer treatment. Bone marrow–derived DCs (BMDCs), which can be generated in large numbers, were prepared, and TBA purified from irradiated mice were bound to their Fc receptors. We hypothesized that TBA–Fc receptor binding on BMDCs would enhance tumor antigen uptake and promote migration to draining lymph nodes.In the B16F10-OVA melanoma model, BMDCs bound with RT-induced TBA generated stronger CTL responses in lymph nodes and tumors, suppressed tumor growth more effectively than standard BMDC vaccination, and provided added benefit when combined with RT. This strategy links the immune-stimulating effects of RT with a personalized cancer vaccine platform and may complement or offer an alternative to ICI-based therapy.日本放射線影響学会第68回大会/第6回アジア放射線研究会議（JRRS/ACRR2025）合同大会conference presentatio
In vivo deep-brain microscopy at submicrometer resolution with refractive indexmatched prism interfaces
No full text第 8 回適応回路センサス領域会議にて「In vivo deep-brain microscopy at submicrometer resolution with refractive indexmatched prism interfaces」の演題でポスター発表を行う。第 8回適応回路センサス領域会議conference poste
Structure-based and AI-accelerated Drug Screening with Enhanced Accuracy
No full textStructure-based virtual screening (SBVS) remains one of the most widely adopted strategies in modern computer-aided drug discovery, yet it continues to suffer from high false-positive rates due to imprecise scoring functions and limited scalability. To address these challenges, we developed a statistical re-scoring framework based on Log-Odds (LOD) scores that quantifies the probability of a docking pose being a “true binder” versus a “decoy”. By integrating this with an AI accelerator, we aim to eliminate the need for exhaustive docking simulations for SBVS in the future.第12回「富岳」を中核とするHPCIシステム利用研究課題 成果報告会conference poste
Diode-based Row-Column Multiplexing Circuits for the TOFPET2 ASIC Module
No full textThe multiplexing technique is essential to reduce the complexity of clinical positron emission tomography (PET) systems. In this study, we developed a diode-based row column multiplexing circuit dedicated to the TOFPET2 ASIC module for our next generation whole gamma imaging (WGI) systems. The WGI systems consist of dual detector rings, and we used two different detector designs, the one-to-one coupling detector with time-of-flight (TOF) capability for the outer ring and the crosshair light sharing (CLS) detector with both TOF and depth-of-interaction capability for the inner ring. The one-to-one coupling detector consisted of an 8×8 array of fast-LGSO crystals (3.1×3.1×20 mm3) and an 8×8 silicon photomultiplier (SiPM) array (Hamamatsu, S14161-3050HS). The CLS detector consisted of a 14×14 array of fast-LGSO crystals (1.45×1.45×15 mm3) and the same type of 8×8 SiPM array. The TOFPET2 ASIC module was used for data acquisition. For coincidence detection, a pair of two identical detectors was used. Two types of row-column multiplexing circuits with a diode and a resistor were developed. For the one-to-one coupling detector, the coincidence timing resolution (CTR) were degraded about 18% and 45% with the diode and resistor multiplexing, respectively. For the CLS detector, the CTR was degraded about 23% and 51% with the diode and resistor multiplexing, respectively. In conclusion, the diode-based multiplexing enhanced the CTR compared to that of the resistor-based multiplexing. In the future, we plan to investigate the optimal diode model to further improve the CTR.2025 IEEE NSS MIC RTSDconference poste
核医学の歴史と将来像
No full text創薬研究開発における放射線・放射性同意元素を用いた技術の活用および普及、更にそれらの安全管理の確保と資質の向上を目的に、放射性医薬品開発の歴史を辿り、我が国並びにQSTにおける同開発に関する今後の展開について述べる2025 年製薬放射線研修会conference presentatio
抗体治療抵抗性子宮体部漿液性がん腹膜播種に対する標的アルファ線治療
No full textUterine serous carcinoma (USC) is a rare aggressive type 2 endometrial carcinoma and often has peritoneal metastasis even in early stage Trastuzumab, the anti-HER2 antibody, has been clinically used against HER2 positive USC, however the antibody treatment resistance has been remain as an issue.Targeted alpha therapy (TAT) is useful for metastasis and has high potential to overcome antibody treatment resistance. The alpha-particle effectively kill the cells by inducing irreparable DNA damages, which is different from how trastuzumab works. Astatine 211 (At-211) is one of the attractive α-particle emitters. We have demonstrated experimental TAT using [At-211]-trastuzumab to HER2 positive USCPM mouse model to investigate the therapeutic efficacy and toxicity. We will discuss the potential of TAT as a novel therapeutic option for antibody treatment resistant PM of HER2 positive USC.第65回日本核医学会学術総会conference presentatio
膵臓がん炭素線治療計画における消化管内ガス影響の評価
No full text[目的]膵臓がんは放射線抵抗性を示す一方、放射線感受性の高い消化管が近接しているため、局所制御率向上には高い線量集中性が求められる。炭素線治療は優れた線量集中性と高い生物学的効果により、良好な治療成績が報告されているが、消化管内のガス移動により飛程が変化し、線量分布に影響を及ぼす可能性がある。本研究の目的は、治療期間中の消化管内ガス変化が線量分布に与える影響を評価することである。[方法]炭素線治療が実施された6症例の治療計画用CT画像を用いて治療計画を行った。ガス領域を組織置換したCT画像を用いて線量分布の再計算を実施し、置換前後の線量分布を比較した。ビーム照射方向には、実治療に使用された4門照射と背側方向からの2門照射を用い、それぞれ評価した。[結果]6例中5例では、2門・4門いずれも置換前後でD95_PTVは1%未満の変化であった。4門照射において、90度方向のビームパス上のガス体積が大きい症例では、ターゲット線量の低下および消化管線量の増加が生じた。2門照射では、4門照射と同じ線量制約で計画を行ったことや、ビーム方向数が少ないことで線量分布の調整が制限され、ターゲットの線量制約を満たせない場合があった。[結論]消化管内ガスが線量分布に与える影響は、全体として大きな変化は確認されなかった。しかし、影響が顕著な症例も存在したことから、今後は治療期間中のガス変動を再現するためのシミュレーションおよびシナリオの検討をしていく。日本放射線腫瘍学会第38回学術大会conference poste
Linear energy transfer correction using Al₂O₃:Cr thermoluminescent and radiophotoluminescence glass dosimeters for therapeutic proton dosimetry
No full textSolid-state luminescence dosimeters face challenge in achieving accurate dosimetry in proton therapy owing to the linear energy transfer (LET)-dependent response. In this study, we proposed a two-dosimeter-based methodology to improve the accuracy of proton dosimetry by correcting the LET-dependent response of a radiophotoluminescence glass dosimeter (RPLD) and an Al2O3:Cr-based ceramic-type thermoluminescence dosimeter (TLD) for postal dosimetry. The LET dependent response for the RPLD and Al2O3: Cr TLD was investigated using an unmodulated 235 MeV proton beam delivered by a passive scattering system. Both dosimeters were individually calibrated in terms of the absorbed dose to water using a 6 MV X-ray beam. The luminescence efficiency ratio between the RPLD and Al2O3: Cr TLD ( RPLD, Al2O3 ∶Cr ) was used as an index to determine the LET dependence correction factor for the RPLD and Al2O3: Cr TLD ( kRPLD LET and k Al2O3 ∶Cr LET ). Modulated proton beams with different spread-out Bragg peak (SOBP) widths were used to evaluate the feasibility of the proposed two-dosimeter methodology. RPLD, Al2O3 ∶Cr decreased with increasing LET. kRPLD LET and k Al2O3 ∶Cr LET were fitted using exponential curves. Proton dosimetry based on the proposed methodology underestimated the absorbed dose to water by an averages of 1.88% and 3.21% for RPLD and Al2O3: Cr TLD, respectively. This demonstrated the feasibility of the proposed methodology. Although the method shows promise for LET correction, the uncertainties in the LET-dependent correction factors, namely 2.39% for the RPLD and 5.84% for the Al₂O₃:Cr TLD, indicate the need for further refinement.journal articl