Annual Report 2019
Department of Medical Physics
Hiroyuki Okamoto, Satoshi Nakamura, Shie Nishioka, Kotaro Iijima, Takahito Chiba, Junichi Kuwahara, Keita Kaga, Mihiro Takemori, Hiroki Nakayama, Yuka Urago
Introduction
The role of our department is to conduct quality management for safety in radiotherapy and to establish standard procedures by implementing state-of-the-art radiation therapy in Japan. All our activities are dedicated to cancer patients, and aim to educate and develop radiation oncologists, radiation technologists, and medical physicists. An accelerator-based boron neutron capture therapy (BNCT) system with a Li target was installed in the new facility and an epithermal neutron beam had already been obtained in August of 2015, and the neutron facility passed the governmental inspection for radiation leakage. Now, non-clinical tests, such as physical and biological experiments, have been already done and a clinical trial using the system and a boron-10 compound, which is provided by STELLA PHARMA CORPORATION, has been underway since November, 2019. The first patient was treated on November, 2019, and it was the world’s first treatment of a human 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, MRIdian is used mainly for on-line adaptive radiotherapy in abdominal tumors.
The Team and What We Do
Our department is collaborating with the Department of Radiation Oncology and the Department of Radiological Technology. That is one of the biggest radiation oncology departments in Japan. Four linear accelerators, CyberKnife, MRIdian, four CT-simulators, and 15 treatment planning computers are working together under on-line networks to provide state-of-art precision external beam radiation therapy. In addition to the conventional X-ray and electron therapies, stereotactic irradiations of brain and body tumors and intensity-modulated radiation therapy (IMRT) are performed routinely. Stereotactic brain irradiation is performed with CyberKnife in the treatment of metastatic as well as primary brain tumors. Stereotactic body tumor irradiation is performed in lung and liver tumors under respiratory gating in linear accelerators or CyberKnife. All linear accelerators have on-board kilovoltage CT imagers, allowing to align patient and tumor coordinates precisely. These image guided radiation therapy (IGRT) facilities enable the precise delivery of IMRT in head and neck cancers, brain tumors, prostate cancers, and postoperative cervical cancers. Fiducial markers have been implanted to improve geometric precision of radiation field reproducibility. MRIdian is used mainly for pancreatic cancer, and other upper abdominal cancers in MRI-guided radiotherapy. Brachytherapy is also performed very intensively to improve local control and many patients are referred from all over Japan. For brachytherapy the following modalities are being employed: an Ir-192 high dose rate (HDR) afterloading system including dedicated CT simulator and fluoroscopy, an I-125 seed implantation system, and other low dose rate (LDR) brachytherapy systems using Au grains, and ruthenium eye plaques. The number of patients undergoing HDR brachytherapy continued to rise constantly. This department is the only institution in Tokyo where HDR interstitial as well as intracavitary irradiations can be performed. The HDR interstitial radiation is performed mainly in gynecological, genitourinary, and head and neck tumors. Ruthenium mold therapy is performed by ophthalmologists to treat retinoblastomas and choroidal melanomas. BNCT is also performed to treat patients with angiosarcoma or melanoma as a clinical trial. Although these tumors are rare, the efficacy of treatments are not generally excellent. We also endeavor to apply BNCT to other tumors that are resistant to conventional therapies.
Research activities
The primary interests of the research activities of the department are to establish safe and efficient radiotherapy systems including risk assessment and quality indicators. Next year, a survey study on quality indicators in radiotherapy for domestic institutions will be performed. Under research with Itochu Corporation, implementing AI (artificial intelligence) in radiotherapy has been conducted. The main activity was to evaluate the accuracy of automatic segmentation using AI. Additionally, research and development (R&D) for the accelerator-based BNCT system employing a Li target has been performed in various areas. As a result, the first patient was treated on November, 2019, and it was the first world’s treatment of a human using an accelerator-based BNCT system with a Li target. Since accelerator-based BNCT systems are still in the development phase all over the world, we will continue R&D for them in the next year and beyond, and will also conduct development activities such as the establishment of international standards for accelerator-based BNCT systems.
Clinical trials
One of our activities is to help radiation oncologists conduct clinical trials without any problems. In addition, credentialing process is established in some clinical trials by development of an independent dose assessment system.
Future prospects
A residency program for medical physicists will begin next year. Our development is aimed at an educational environment with state-of-the-art radiotherapy and many staff.
List of papers published in 2019
Journal
1. Igaki H, Nakamura S, Kurihara H, Abe Y, Nishioka S, Fujii R, Nakamura M, Nakayama Y, Morita T, Okamoto H, Imahori Y, Itami J. Comparison of (18)FBPA uptake with (18)FDG uptake in cancer patients. Appl Radiat Isot, 157:109019, 2020
2. Murakami N, Nakamura S, Kashihara T, Kato T, Shibata Y, Takahashi K, Inaba K, Okuma K, Igaki H, Nakayama Y, Galalae R, Itami J. Hyaluronic acid gel injection in rectovaginal septum reduced incidence of rectal bleeding in brachytherapy for gynecological malignancies. Brachytherapy, 19:154-161, 2020
3. Iijima K, Okamoto H, Takahashi K, Aikawa A, Wakita A, Nakamura S, Nishioka S, Harada K, Notake R, Sugawara A, Yoshimura R, Kunieda E, Itami J. Inter-fractional variations in the dosimetric parameters of accelerated partial breast irradiation using a strut-adjusted volume implant. J Radiat Res, 61:123-133, 2020
4. Murakami N, Yoshimoto S, Nakamura S, Uematsu M, Kashihara T, Takahashi K, Inaba K, Okuma K, Igaki H, Nakayama Y, Itami J. Per-oral interstitial brachytherapy catheter insertion for boost in case of recurrent tonsillar carcinoma: dosimetry and clinical outcome. BJR Case Rep, 6:20190059, 2020
5. Okamoto H, Nishioka S, Iijima K, Nakamura S, Sakasai T, Miura Y, Takemori M, Nakayama H, Morishita Y, Shimizu M, Abe Y, Igaki H, Nakayama Y, Itami J. Monte Carlo modeling of a 60Co MRI-guided radiotherapy system on Geant4 and experimental verification of dose calculation under a magnetic field of 0.35 T. J Radiat Res, 60:116-123, 2019