Jump to Main Contents

Home > Specialist ctrs & depts > Section of Radiation Safety and Quality Assurance

Section of Radiation Safety and Quality Assurance

Hidenobu Tachibana, Kenji Hotta, Hiromi Baba, Kana Motegi, Ryo Takahashi, Seigo Kurokawa


Radiation therapy technologies have improved recently and will continue to progress. However, while advanced technology has provided higher accuracy and precision in radiotherapy, it has introduced more complex situations and difficulties in performing the treatment adequately. Radiotherapy errors can occur at several time points from planning through treatment. The accuracy and precision of dose delivery in radiation therapy is important because there is evidence that a 7-10% change in the dose to the target volume may result in a significant change in tumor control probability. “Quality assurance in radiotherapy” is for all procedures that ensure consistency of the medical prescription, and safe fulfillment of that prescription, as regards the dose to the target volume, together with the minimal dose to normal tissue, minimal exposure of personnel and adequate patient monitoring aimed at determining the end result of the treatment.

The primary aim of the Section of Radiation Safety and Quality Assurance is to develop quality assurance programs for photon and proton therapy machines as well as to check that quality requirements in photon and proton therapy products are met and to adjust and correct performance if the requirements are found not to have been met. The second aim is to install and establish advanced technologies in clinical practices in the radiation oncology department. Other goals are to develop high-precision radiotherapy as intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), respiratory-gating radiation therapy, marker-tracking radiation therapy, image-guided radiation therapy (IGRT), stereotactic RT and proton beam therapy (PBT) in cancer treatment.

Routine activities

At present, the staff of the Section of Radiation Safety and Quality Assurance consists of one radiation oncologists, three medical physicists and one radiological technologist. We have more than 1,000 new patients for photon and proton therapy every year. The section is responsible for four linear accelerators, two CT simulators and four different treatment planning systems in photon/ electron therapy. In proton therapy, one accelerator, two treatment units, and one planning system are managed.

Quality assurance programs have been established for photon and proton therapy by the medical physicists. The daily, monthly and annual programs are performed by the medical physicists and radiological technologists. In addition, the medical physicists perform radiotherapy planning for IMRT/VMAT in prostate and head and neck sites, stereotactic RT in the liver and lungs, and proton therapy in the head and neck, esophagus, lung, liver, prostate and infants. The medical physicists support conventional radiotherapy planning and also check the quality and safety for all treatment plans.

Research activities

In the Radiation Safety and Quality Assurance Section, the following research activities are ongoing:

  1. Design and development of new proton beam irradiation system
  2. Design and development of monitor unit calculation for proton therapy
  3. Design and development of a Monte Carlobased dose calculation algorithm for proton therapy
  4. Design and development of a CT-based image guided and adaptive proton therapy system.
  5. Design and development of four-dimensional planning for motion synchronized dose delivery for photon therapy.
  6. Design and development of CT-pulmonary ventilation imaging
  7. Design and development of quality assurance system for gated radiotherapy
  8. Multi-institutional study of independent MU/ Dose verification for conventional, stereotactic RT, IMRT, VMAT as well as for Vero, CyberKnife and Tomotherapy in photon therapy

Clinical trials

The following multi-institutional clinical trials are ongoing:

  1. Establishment of safety for radiotherapy planning of photon therapy


We established an on-the job-training program for quality assurance programs for a photon linear accelerator and over 100 medical physicists and radiological technologists have taken the educational program. We held a meeting for independent MU/dose verification and over 180 medical physicists and radiological technologists participated in the meeting. We trained graduated students from Tsukuba University and Komazawa University for a quality assurance program in photon therapy

Future prospects

We maintain the quality of photon/electron and proton therapy machines and also establish new technologies to improve patient outcomes. In addition, we will work on radiotherapy as well as radiology including establishment of a quality assurance program for diagnostic instruments and management of radioactive materials.

List of papers published

  1. Tachibana H,  Watanabe Y, Mizukami S, Maeyama T, Terazaki T, Uehara R, Akimoto T, "End-to-end delivery quality assurance of computed tomography-based high-dose-rate brachytherapy using a gel dosimeter”, Brachytherapy 19, 362-371, 2020
  2.  Nishio T, Tachibana H, Kase Y, Hotta K, Nakamura M, Tamura M, Terunuma T, Toshito T, Yamashita H, Ishikura S, Fuji H, Akimoto T, Nishimura Y, “Liver phantom design and dosimetric verification in participating institutions for a proton beam therapy in patients with resectable hepatocellular carcinoma: Japan Clinical Oncology Group trial (JCOG1315C),” Radiother Oncol 29, 98-104, 2019.
  3. Motegi K, Tachibana H, Motegi A, Hotta K, Baba H, Akimoto T, "Usefulness of hybrid deformable image registration algorithms in prostate radiation therapy”, J Appl Clin Med Phys, 229-236, 2019.
  4. Hojo H, Dohmae T, Hotta K, Kageyama S, Baba H, Kohno R, Motegi A, Tsuchihara K, Akimoto T. Effect of 5-fluorouracil on Cellular Response to Proton Beam in Esophageal Cancer Cell Lines According to the Position of Spread-Out Bragg Peak. Acta Oncol. 2019;58(4):475-482.
  5. Yamaguchi M, Ohnuki K, Hotta K, Fujii H, “MR Signal Changes in Superparamagnetic Iron Oxide Nanoparticle-Labeled Macrophages in Response to X Irradiation,” NMR Biomed . 2019;32(9):e4132.
  6. Nakamura N, Hotta K, Zenda S, Baba H, Kito S, Akita T, Motegi A, Hojo H, Nakamura M, Parshuram RV, Okumura M, Akimoto T. “Hypofractionated proton beam therapy for centrally located lung cancer,” J Med Imaging Radiat Oncol. 2019;63(4):552-556.
  7. Nakamura N, Hojo H, Inoue K, Hotta K, Zenda S, Baba H, Onozawa M, Motegi A, Nakamura M, Kibe Y, Akimoto T. Late radiological changes after passive scattering proton beam therapy for Stage I lung cancer. J Radiat Res. 2018 1;59(4):456-461.
  8. Hojo H, Dohmae T, Hotta K, Kohno R, Motegi A, Yagishita A, Makinoshima H, Tsuchihara K, Akimoto T. Difference in the relative biological effectiveness and DNA damage repair processes in response to proton beam therapy according to the positions of the spread out Bragg peak. Radiat Oncol. 2017;12(1):111.
  9. Matsubayashi F, Takahashi R, Kamima T, Sato Y, Sato T. [Influence of Respiratory Phase during Image Acquisition on Prescribed Dose in Image Guided Radiation Therapy Using Implant Marker for Prostate Cancer]. Nihon Hoshasen Gijutsu Gakkai Zasshi. 2019;75(12):1394-1402.
  10. Kamima T, Yoshioka M, Takahashi R, Sato T. [Impact of DVH Outliers Registered in Knowledge-based Planning on Volumetric Modulated Arc Therapy Treatment Planning for Prostate Cancer]. Nihon Hoshasen Gijutsu Gakkai Zasshi. 2019;75(2):151-159.
  11. Murakami Y, Magome T, Matsubayashi F, Takahashi R, Arima M, Kamima T, Nakano M, Sato T, Yoshioka Y, Oguchi M. Evaluation of organ-at-risk dose reduction with jaw tracking technique in flattening filter-free beams in lung stereotactic body radiation therapy. Phys Med. 2019 May;61:70-76.
  12. Tachibana H, Uchida Y, Miyakawa R, Yamashita M, Sato A, Kito S, Maruyama D, Noda S, Kojima T, Fukuma H, Shirata R, Okamoto H, Nakamura M, Takada Y, Nagata H, Hayashi N, Takahashi R, Kawai D, Itano M, "Multi-institutional comparison of secondary check of treatment planning using computer-based independent dose calculation for non-C-arm linear accelerators”, Phys Med 56, 58-65, 2018.
  13. Moriya S, Tachibana H, Hotta K, Nakamura N, Sakae T, Akimoto T, "Range optimization for target and organs at risk in dynamic adaptive passive scattering proton beam therapy - a proof of concept”, Phys Med 56, 66-73, 2018
  14. Kumazaki Y, Ozawa S, Nakamura M, Kito S, Minemura T, Tachibana H, Nishio T, Ishikura S, Nishimura Y, “An end-to-end postal audit test to examine the coincidence between the T imaging isocenter and treatment beam isocenter of the IGRT linac system for Japan Clinical Oncology Group (JCOG) clinical trials,” Phys Med 53, 145-152, 2018.
  15. Tachibana H, Motegi K, Moriya S. “Impact of shoulder deformation on volumetric modulated arc therapy doses for head and neck cancer,” Phys Med 53, 118-128, 2018.
  16. Miyakawa S, Tachibana H, Moriya S, Kurosawa T, Nishio T, Sato M, "Design and development of a non-rigid phantom for the quantitative evaluation of DIR-based mapping of simulated pulmonary ventilation,” Med Phys 45, 3496-3505, 2018.
  17. Miyakawa S, Tachibana H, Moriya S, Kurosawa T, Nishio T, "Evaluation of deformation parameters for deformable image registration-based ventilation imaging using an air-ventilating non-rigid phantom,” Phys Med 50, 20-25, 2018.
  18. Takahashi R, Kamima T, Itano M, Yamazaki T, Ishibashi S, Higuchi Y, Shimizu, H Yamamoto T, Yamashita M, Baba H, Sugawara Y, Sato A, Nishiyama S, Kawai D, Miyaoka S, and Tachibana H, A multi-institutional study of secondary check of treatment planning using Clarkson-based dose calculation for three-dimensional radiotherapy, Phys Med 49, 19-27, 2018.
  19. Jinno S, Tachibana H, Moriya S, Mizuno N, Takahashi R, Kamima T, Ishibashi S and Sato M, “A multi-institutional study of independent calculation verification in inhomogeneous media using a simple and effective method of heterogeneity correction integrated with the Clarkson method,” J Radiat Res 1-11, 2018.
  20. Hirano Y, Onozawa M, Hojo H, Motegi A, Zenda S, Hotta K, Moriya S, Tachibana H, Nakamura N, Kojima T, Akimoto T, “Dosimetric comparison between proton beam therapy and photon radiation therapy for locally advanced esophageal squamous cell carcinoma,” Radiat Oncol 13, 23, 2018.
  21. Yamashita M, Takahashi R, Kokubo M, Takayama K, Tanabe H, Sueoka M, Ishii M and Tachibana H, “A feasibility study of independent verification of dose calculation for Vero4DRT using a Clarkson-based algorithm,” Med Dosim S0958-3947, 30142-5, 2018.
  22. Kamima T, Baba H, Takahashi R, Yamashita M, Sugawara Y, Kawai D, Yamamoto T, Sato A, Tachibana H, “Multi-institutional comparison of computer-based independent dose calculation for intensity modulated radiation therapy and volumetric modulated arc therapy,” Phys Med 45, 72-81, 2018.
  23. Uchida Y, Tachibana H, Kamei Y, Kashihara K, "Effectiveness of a simple and real-time baseline shift monitoring system during stereotactic body radiation therapy of lung tumors," Phys Med 43, 100-106, 2017.
  24. Kurosawa T, Tachibana H, Moriya S, Miyakawa S, Nishio T, Sato M, “Usefulness of a new online patient-specific quality assurance system for respiratory-gated radiotherapy,” Phys Med 43, 63-72, 2017.
  25. Sugawara Y, Tachibana H, Kadoya N, Kitamura N, Sawant A, Jingu K, “Prognostic factors associated with the accuracy of deformable image registration in lung cancer patients treated with stereotactic body radiotherapy,” Med dosim. 42, 326-333, 2017.
  26. 山崎 健史,板野 正信,石橋 悟,樋口 義洋, 山下 幹子,小浴 恵,小林 望美,橘 英伸.セカンダリチェックにおける独立計算検証システムの違いの影響.医学物理.第36巻 197-206,2017.
  27. 清水 裕之,板野 正信,山崎 健史,高橋 良,上間 達也,山下 幹子,馬場 大海,石橋 悟, 樋口 義洋,山本 鋭二郎,菅原 康晴,佐藤 礼,西山 史朗,宮岡 聡,河合 大輔,橘 英伸.ウエッジ利用時の軸外線量比の独立計算の精度.医学物理.第36巻 188-196,2017.
  28. Kawai D, Takahashi R, Kamima T, Baba H, Yamamoto T, Kubo Y, Ishibashi S, Higuchi Y, Tani K, Mizuno N, Jinno S, Tachibana H, " Variation of the prescription dose using the analytical anisotropic algorithm in lung stereotactic body radiation therapy," Phys Med. 38, 98-104, 2017.
  29. Moriya S, Tachibana H, Hotta K, Nakamura N, Takeji S, Akimoto T, “Feasibility of dynamic adaptive passive scattering proton therapy with computed tomography image guidance in the lung,” Med Phys 4474-4481, 2017
  30. Nishiyama S, Ishibashi S, Takahashi R, Tachibana H, Independent dose verification for brain stereotactic radiotherapy using different add-on micro multi-leaf collimators. Radiol Phys Technol. 1-8, 2017
  31. Nakamura N, Zenda S, Tahara M, Okano S, Hayashi R, Hojo H, Hotta K, Kito S, Motegi A, Arahira S, Tachibana H, Akimoto T. Proton beam therapy for olfactory neuroblastoma. Radiother Oncol. 122, 368-372, 2017.
  32. Moriya S, Tachibana H, Kitamura N, Sawant A, Sato M, Dose warping performance in deformable image registration in lung. Phys Med. 37, 16-23, 2017.
  33. Wu CT, Motegi A, Motegi K, Hotta K, Kohno R, Tachibana H, Kumagai M, Nakamura N, Hojo H, Niho S, Goto K, Akimoto T. Dosimetric comparison between proton beam therapy and photon radiation therapy for locally advanced non-small cell lung cancer. Jpn J Clin Oncol. 1-7, 2016.
  34. Kohno R, Yamaguchi H, Motegi K, Hotta K, Nishioka S, Akimoto T. In Vivo Dosimetry of an Anthropomorphic Phantom Using the RADPOS for Proton Beam Therapy, International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 5 (3), 177-183, 2016.
  35. Mizutani S, Takada Y, Kohno R, Hotta K, Tansho R, Akimoto T. Application of Dose Kernel Calculation Using a Simplified Monte Carlo Method to Treatment Plan for Scanned Proton Beams. J Appl Clin Med Phys . 2016;17(2):315-327.
  36. Kohno R , Yamaguchi H , Motegi K., Tanaka F , Akita T , Nagata Y , Hotta K , Miyagishi T, Nishioka S, Dohmae T and Akimoto T. Position Verification of the RADPOS 4-D In-Vivo Dosimetry System. International Journal of Medical Physics, Clinical Engineering and Radiation Oncology, 4, 318-325, 2015.
  37. Hotta K, Kohno R, Nagafuchi K, Yamaguchi H, Tansho R, Takada Y, Akimoto T. “Evaluation of Monitor Unit Calculation Based on Measurement and Calculation With a Simplified Monte Carlo Method for Passive Beam Delivery System in Proton Beam Therapy,” J Appl Clin Med Phys . 2015;16(5):228-238.