Annual Report 2018
Department of Medical Physics
Hiroyuki Okamoto, Satoshi Nakamura, Shie Nishioka, Kotaro Iijima, Junichi Kuwahara, Keita Kaga, Mihiro Takemori, Hiroki Nakayama
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. A linear accelerator for the hospital-based boron neutron capture therapy (BNCT) was installed in the new facility and an epithermal neutron beam was obtained in August 2015 and the neutron facility passed the governmental inspection for radiation leakage. Now the stability of the BNCT accelerator is established and physical and biological experiments are under way. Additionally, the 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 stateof-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, which help 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, which is the fusion of MRI and a radiation therapy machine, is used mainly for pancreatic cancer, and other upper abdominal cancers. Brachytherapy is also performed very intensively to improve local control and many patients are referred to 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.
Research activities
The primary interests of the research activities of the department are 1) to establish safe and efficient radiotherapy systems, 2) to establish risk assessment for on-line adaptive radiotherapy, 3) to establish an independent dose assessment system in external radiotherapy and brachytherapy, 4) to develop efficient procedures in treatment planning systems using Artificial Intelligence, 5) to develop in-vivo dosimetry without invasions to patients, 6) to develop three dimensional dosimetry, and 7) to develop an accelerator-based BNCT system.
Clinical trials
One of our activities is to help radiation oncologists conduct clinical trials without any problems. In addition, a credentialing process is established in some clinical trials by development of an independent dose assessment system.
Future prospects
Our department needs to establish a residency program for medical physicists in Japan. Our development is aimed at an educational environment with state-of-the-art radiotherapy and many staff.
List of papers published in 2018
Journal
1. 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 035 T. J Radiat Res, 60:116-123, 2019. pii: rrz061.
2. 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, 2019
3. Okamoto H, Murakami N, Isohashi F, Kasamatsu T, Hasumi Y, Iijima K, Nishioka S, Nakamura S, Nakamura M, Nishio T, Igaki H, Nakayama Y, Itami J, Ishikura S, Nishimura Y, Toita T. Dummy-run for standardizing plan quality of intensity-modulated radiotherapy for postoperative uterine cervical cancer: Japan Clinical Oncology Group study(JCOG1402). Radiat Oncol, 14:133, 2019
4. Murakami N, Isohashi F, Hasumi Y, Kasamatsu T, Okamoto H, Nakamura K, Shibata T, Ito Y, Ishikura S, Nishimura Y, Yaegashi N, Toita T. Single-arm confirmatory trial of postoperative concurrent chemoradiotherapy using intensity modulated radiation therapy for patients with high-risk uterine cervical cancer: Japan Clinical Oncology Group study (JCOG1402). Jpn J Clin Oncol, 49:881- 885, 2019
5. Nakamura S, Igaki H, Ito M, Okamoto H, Nishioka S, Iijima K, Nakayama H, Takemori M, Imamichi S, Kashihara T, Takahashi K, Inaba K, Okuma K, Murakami N, Abe Y, Nakayama Y, Masutani M, Nishio T, Itami J. Characterization of the relationship between neutron production and thermal load on a target material in an accelerator-based boron neutron capture therapy system employing a solid-state Li target. PLoS One, 14:e0225587, 2019
6. Murakami N, Mori T, Nakamura S, Yoshimoto S, Honma Y, Ueno T, Kobayashi K, Kashihara T, Takahashi K, Inaba K, Okuma K, Igaki H, Nakayama Y, Itami J. Prognostic value of the expression of epithelial cell adhesion molecules in head and neck squamous cell carcinoma treated by definitive radiotherapy. J Radiat Res, 60:803-811, 2019
7. Umezawa R, Inaba K, Nakamura S, Wakita A, Okamoto H, Tsuchida K, Kashihara T, Kobayashi K, Harada K, Takahashi K, Murakami N, Ito Y, Igaki H, Jingu K, Itami J. Dose escalation of external beam radiotherapy for high-risk prostate cancer-Impact of multiple high-risk factor. Asian J Urol, 6:192-199, 2019
8. Kashihara T, Murakami N, Iizumi S, Sakamoto Y, Nakamura S, Iijima K, Takahashi K, Inaba K, Okuma K, Igaki H, Nakayama Y, Okusaka T, Uno T, Itami J. Hemorrhage from Ascending Colon and Gluteal Muscle Associated with Sorafenib and Radiation Therapy: Radiation Dose Distribution Corresponded with Colonoscopy Findings and Computed Tomography Images. Pract Radiat Oncol, 2019
9. Nakamura S, Igaki H, Okamoto H, Wakita A, Ito M, Imamichi S, Nishioka S, Iijima K, Nakayama H, Takemori M, Kobayashi K, Abe Y, Okuma K, Takahashi K, Inaba K, Murakami N, Nakayama Y, Nishio T, Masutani M, Itami J. Dependence of neutrons generated by 7Li(p,n) reaction on Li thickness under free-air condition in accelerator-based boron neutron capture therapy system employing solid-state Li target. Phys Med, 58:121-130, 2019