Annual Report 2024
Section of Radiation Safety and Quality Assurance
Hiroyuki Okamoto, PhD (chief medical physicist), Satoshi Nakamura, PhD (medical physicist), Takahito Chiba, Msc (medical physicist), Hiroki Nakayama, PhD (medical physicist), Tetsu Nakaichi, PhD (medical physicist), Masataka Ueda, Msc (radiation technologist), Miki Yonemura, PhD (resident medical physicist), Riki Oshika, Msc (resident medical physicist), Yuta Kobayashi, Msc (resident medical physicist), Hironori Kishida, Msc (resident medical physicist), Kazuya Seki, Msc(resident medical physicist), Shoki Nakamura, Msc(resident medical physicist), Masato Nishitani, Msc, Syuka Nishina, Msc, Hana Endo, Bsc, Issa Endo, Bsc
Introduction
The role of our department is to perform quality management for safety in radiotherapy and to establish standard procedures by implementing state-of-the-art radiotherapy in Japan. All our activities are dedicated to cancer patients; thus, our mission is to educate and develop the expertise of radiation oncologists, radiation technologists, and medical physicists for safe, high precision radiotherapy. Our primary task is to comprehensively review treatment plans for preventing human error in clinical practice. In addition, our mainly task is to create treatment plans for stereotactic radiotherapy (SRT), intensity-modulated radiotherapy (IMRT), brachytherapy with collaboration to the department of radiological technology for safe radiotherapy. An accelerator-based boron neutron capture therapy (BNCT) system with a Li target was installed in the new facility and an epithermal neutron beam was obtained in August of 2015; the neutron facility passed the governmental inspection for radiation leakage. Non-clinical tests, such as physical and biological experiments, have been performed and a clinical trial using the system and a boron-10 compound, which is provided by STELLA PHARMA CORPORATION, has been conducted since November 2019. The first patient was treated in November 2019, and it was the first-in-human treatment in the world using an accelerator-based BNCT system with a Li target. Additionally, an MRI-guided radiation therapy machine (MRIdian) was introduced for the first time in Japan. After strict acceptance and commissioning procedures, the MRIdian is used mainly for online adaptive radiotherapy in abdominal tumors.
The Team and What We Do
Our division’s principal research activities are conducted in close collaboration with the Department of Radiation Oncology and Radiological Technology. From a medical-physics standpoint, we pursue (i) the technical development of high-precision radiotherapy, (ii) the proposal and validation of novel quality-assurance (QA) methodologies, and (iii) foundational investigations into medical safety together with the establishment of institutional implementation frameworks. We also provide administrative support, including physics QA for clinical trials. In 2024, the National Cancer Center Research and Development Fund (2022-A-18; Principal Investigator: Hiroyuki Okamoto; project title: “Establishing Implementation Systems for High-Precision Radiotherapy and Research on Medical Safety”) entered its third term. In partnership with relevant professional societies, we conducted joint research and seminars on medical safety in radiotherapy. We advanced initiatives to (a) introduce quality indicators (QIs) for medical safety in radiotherapy; (b) support the establishment and dissemination of risk-analysis practices for patient safety; (c) develop implementation frameworks to promote next-generation radiotherapy and establish guideline-based QA procedures; and (d) produce patient-education videos. With respect to the comprehensive review method linking radiotherapy treatment plans and the medical record as outlined by AAPM Task Group 275, we completed a Japanese translation in the preceding year and distributed it to participants at the 37th Annual Meeting of the Japanese Society for Radiation Oncology (JASTRO) held in November 2024. In collaboration with the national association of medical physicists, we also delivered a hands-on seminar on treatment-plan review utilizing this text. In BNCT, a phaseⅠclinical trial of a patient with angiosarcoma or melanoma had been completed in 2022 and we participated in the clinical trial. The phaseⅠclinical trial revealed that the efficacy of BNCT on those tumors was excellent, although those tumors were rare and efficacy of standard treatments was not generally sufficient. Therefore, based on the result of the phaseⅠclinical trial, a phaseⅡclinical trial of a patient with angiosarcoma has been conducted since 2022 and we have also participated in the clinical trial. Furthermore, we also make efforts to apply BNCT to other tumors that are resistant to conventional therapies.
Research Activities
The main research activities of our division are the development of highly-advanced radiotherapy techniques, development of quality control methods, and basic research on medical safety in cooperation with the radiotherapy department from medical physics aspects. In 2023, the National Cancer Center Research and Development Fund (2022-A-18, Chief Hiroyuki Okamoto, researchers our staff) started to launch several projects, e.g., the establishment of a medical care team involving radiotherapy, introduction of a Quality Indicator (QI) for medical safety in radiotherapy, clinically implementation of risk analysis in radiotherapy, and establishment of an implementation system and guidelines for advanced radiation therapy such as BNCT and MR-guided radiation therapy. These projects must be promoted by cooperation with other organizations.
In addition, we have continued research and development (R&D) for the accelerator-based BNCT system employing the Li target to expand indications in BNCT and to become safe and efficient system. We also participated in a PhaseⅠtrial on the accelerator-based BNCT system to perform BNCT effectively and safely. As a result, the trial was then completed without any problems. Furthermore, based on the excellent results of the PhaseⅠtrial, a PhaseⅡtrial for angiosarcoma has been conducted and we have also participated in the trial.
The accelerator-based BNCT system is still in the development phase worldwide. We initiated the activities for establishing the international standards of the accelerator-based BNCT system. As a result, the international standard (International Electrotechnical Commission standard) for the accelerator-based BNCT system was proposed by Japan team in which we participated. It was the first time for the Japan team to propose the international standard for the equipment of radiation therapy. In addition, we have been conducting basic research for establishing international standards.
Clinical Trials
One of our activities is to help radiation oncologists to conduct clinical trials without any problems. In addition, the credentialing process has been established in certain clinical trials by development of an independent dose assessment system.
Education
We provided educational guidance to medical physicists and radiology technologists as an instructor for medical safety seminars and medical physics-related seminars at related academic societies. In addition, the medical physicist residency system was started in 2021, and medical physics-related lectures were given to medical physicist residents and new employees regardless of their position in the department. Within the radiotherapy department, radiotherapy process training was conducted for radiation technologists and medical physicists. This is a training session to confirm the entire radiotherapy process with multiple professions.
Future Prospects
In collaboration with the radiotherapy departments (the Department of Radiation Oncology and the Department of Radiological Technology), we have established a system to safely implement high-precision radiotherapy such as intensity-modulated radiotherapy, image-guided radiotherapy, stereotactic radiotherapy, respiratory gated radiotherapy, and brachytherapy. We need to propose various measures through related academic societies with reference to our radiotherapy system. We would also like to promote the development of cutting-edge radiotherapy technologies such as MR image-guided radiotherapy and BNCT. In addition, we need to promote a medical physicist residency program with the goal of developing leaders in the field of medical physics by taking advantage of the unique features of our radiotherapy department.
List of papers published in 2024
Journal
1. Takahashi K, Kagami Y, Yoshimura R, Morota M, Murakami N, Nakamura S, Okamoto H, Nagao A, Sakuramachi M, Kashihara T, Kaneda T, Inaba K, Okuma K, Nakayama Y, Itami J, Igaki H. Prospective study of once-daily accelerated partial breast irradiation using 3-dimensional conformal external beam radiotherapy for Japanese women: 12-year outcomes, toxicity, and cosmesis. Breast Cancer. 2025 Jan;32(1):197-207. doi: 10.1007/s12282-024-01650-x. Epub 2024 Dec 4.
2. Iijima K, Nakayama H, Nakamura S, Chiba T, Shuto Y, Urago Y, Nishina S, Kishida H, Kobayashi Y, Takatsu J, Kuwahara J, Aikawa A, Goka T, Kaneda T, Murakami N, Igaki H, Okamoto H. Analysis of human errors in the operation of various treatment planning systems over a 10-year period. J Radiat Res. 2024;65(5):603-18.
3. Imamichi S, Ito T, Tong Y, Gao Z, Arai Y, Fujimori H, Chen L, Sanada Y, Nakamura S, Murakami Y, Ishiai M, Suzuki M, Itami J, Igaki H, Masunaga S, Masutani M. Transcriptome analysis of human oral squamous cancer SAS cells as an early response after boron neutron capture therapy. Appl Radiat Isot. 2025;218:111648.
4. Kashihara T, Nakamura S, Igaki H. Response to 'Pioneering BNCT: Refining strategies for complex cutaneous malignancies. Radiother Oncol. 2025;206:110787.
5. Kashihara T, Nakamura S, Yamazaki N, Takahashi A, Namikawa K, Ogata D, Nakano E, Okuma K, Kaneda T, Mori T, Ito K, Itami J, Shimada K, Nakagama H, Igaki H. Boron neutron capture therapy for cutaneous angiosarcoma and malignant melanoma: First in-human phase I clinical trial. Radiother Oncol. 2025;202:110607.
6. Kashihara T, Urago Y, Okamoto H, Takemori M, Nakayama H, Mikasa S, Nakaichi T, Iijima K, Chiba T, Kuwahara J, Nakamura S, Chang W, Matsui Y, Igaki H. A preliminary study on rectal dose reduction associated with hyaluronic acid implantation in brachytherapy for prostate cancer. Asian J Urol. 2024;11(2):286-93.
7. Kobayashi Y, Nakamura S, Takemori M, Nakaichi T, Shuto Y, Ito K, Takahashi K, Kashihara T, Yonemura M, Endo H, Kunito K, Okamoto H, Chiba T, Nakayama H, Oshika R, Kishida H, Itami J, Kurihara H, Igaki H. Comparison of dose distribution with and without reflecting heterogeneous boron distribution using (18)F-BPA positron emission tomography in boron neutron capture therapy. Appl Radiat Isot. 2025;219:111720.
8. Kurokawa S, Okamoto H, Nakaichi T, Mikasa S, Nakamura S, Iijima K, Chiba T, Nakayama H, Kashihara T, Inaba K, Igaki H. Machine learning prediction for lung dose in locally advanced esophageal cancer using volumetric modulated arc therapy. Med Dosim. 2025.
9. Nagao A, Murakami N, Sakuramachi M, Kashihara T, Takahashi K, Kaneda T, Inaba K, Okuma K, Okamoto H, Nakayama Y, Yonemori K, Igaki H. Role of the gel spacer in safely delivering whole pelvic radiation therapy without central shielding in computed tomography-based image-guided adaptive brachytherapy for uterine cervical cancer patients. Brachytherapy. 2024;23(5):595-603.
10. Nakamura S, Takemori M, Nakaichi T, Shuto Y, Kashihara T, Iijima K, Chiba T, Nakayama H, Urago Y, Nishina S, Kobayashi Y, Kishida H, Imamichi S, Takahashi K, Masutani M, Okamoto H, Nishio T, Itami J, Igaki H. A method for delivering the required neutron fluence in an accelerator-based boron neutron capture therapy system employing a lithium target. Sci Rep. 2024;14(1):11253.
11. Nakamura S, Tanaka H, Kato T, Akita K, Takemori M, Kasai Y, Kashihara T, Takai Y, Nihei K, Onishi H, Igaki H. A national survey of medical staffs' required capability and workload for accelerator-based boron neutron capture therapy. J Radiat Res. 2024;65(5):712-24.
12. Nishitani M, Okamoto H, Nakamura S, Iijima K, Chiba T, Nakayama H, Nakaichi T, Takemori M, Urago Y, Chang W, Igaki H. A new approach to assess transit dose impact in gynecological and prostate brachytherapy with effective transit time. J Contemp Brachytherapy. 2024;16(6):449-56.
13. Okamoto H, Nonaka M, Chiba T, Kaneda T, Kobayashi Y, Nakamura S, Nakayama H, Iijima K, Shuto Y, Yonemura M, Oshika R, Kishida H, Urago Y, Nishitani M, Nishina S, Sakamoto T, Shibata Y, Goka T, Igaki H. Dosimetric impact of the respiratory motion of the liver dome in stereotactic body radiotherapy for spine metastasis: A planning study. J Appl Clin Med Phys. 2024;25(9):e14403.
14. Okamoto H, Sakuramachi M, Yatsuoka W, Ueno T, Katsura K, Murakami N, Nakamura S, Iijima K, Chiba T, Nakayama H, Shuto Y, Takano Y, Kobayashi Y, Kishida H, Urago Y, Nishitani M, Nishina S, Arai K, Igaki H. A novel method for determining dose distribution on panoramic reconstruction computed tomography images from radiotherapy computed tomography. Imaging Sci Dent. 2024;54(2):129-37.
15. Takada M, Yagi N, Nakamura S, Shimada K, Itami J, Igaki H, Nakamura M, Nunomiya T, Endo S, Kajimoto T, Tanaka K, Aoyama K, Narita M, Nakamura T. Development of an online neutron beam monitoring system for accelerator-based boron neutron capture therapy in a hospital. Med Phys. 2025;52(1):605-18.
16. Yoshimura RI, Toda K, Watanabe H, Miura M, Notake R, Murakami N, Igaki H, Nakamura S, Umezawa R, Kadoya N, Jingu K, Itami J. Efficacy and safety of diffusing alpha-emitter radiation therapy (DaRT) for head and neck cancer recurrence after radiotherapy. Int J Clin Oncol. 2025.
17. Zenda S, Kashihara T, Saito T, Okamoto H, Kadoya N, Chiba T, Noda SE, Kawaguchi T, Jingu K, Shibuya K, Uno T, Igaki H. Two-fractionated stereotactic magnetic resonance-guided adaptive radiation therapy for patients with prostate cancer (SMART PRO trial): protocol for a confirmatory clinical trial. BMJ Open. 2024;14(8):e082899.
18. Kojima T, Okamoto H, Kurooka M, Tohyama N, Tsuruoka I, Nemoto M, Shimomura K, Myojoyama A, Ikushima H, Ohno T, Ohnishi H, Current status of the working environment of brachytherapy in Japan: a nationwide survey-based analysis focusing on radiotherapy technologists and medical physicists, J Radiat Res. 2024 Oct 24;65(6):851–861.
19. Ota S, Yasui K, Ogata T, Mori Y, Nishio T, Tohyama N, Okamoto H, Kurooka M, Shimomura K, Kojima T, Onishi H, Clinical workload profile of medical physics professionals at particle therapy Centers: a National Survey in Japan,J Radiat Res. 2024 Dec 9;66(1):52–64.
20. Takada M, Yagi N, Shimada K, Fujii R, Nakamura M, Nakamura S, Kato S, Nunomiya T, Aoyama K, Narita M, Nakamura T. Novel approach to long-term monitoring of accelerator-based boron neutron capture therapy. Med Phys. 2025
21. Matsubayashi N, Hu N, Takata T, Sasaki A, Kumada H, Nakamura S, Masuda A, Tanaka H. Characterization of acrylic phantom for use in quality assurance of BNCT beam output procedure. J Radiat Res. 2025;66(1):10-15.
22. Ishikawa A, Tanaka H, Nakamura S, Kumada H, Sakurai Y, Watanabe K, Yoshihashi S, Tanagami Y, Uritani A, Kiyanagi Y. Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy. J Radiat Res. 2024;65(6):765-775.
23. Nakaichi T, Funamoto K, Yamashita S, Yamamoto H, Yokoyama K. Clinical Usefulness of Standardized Uptake Value Normalized to Lean Body Mass Measured Using a Body Composition Analyzer. Cureus. 2025 May 30;17(5):e85089. doi: 10.7759/cureus.85089. PMID: 40589668; PMCID: PMC12208517.