Hokkaido University Graduate School of Biomedical Science and Engineering


Radiation Medical Physics

Associate Professor
Seishin Takao
Hokkaido University Researcher Database

Assistant Professor, Graduate School of Biomedical Science and Engineering
Assistant Professor, Department of Medical Physics, Hokkaido University Hospital
Assistant Professor, Division of Quantum Science and Engineering, Faculty of Engineering (concurrent)
Ph.D. in Engineering, Graduate school of Engineering, Hokkaido University (2009)

License:Medical physicist
Research field:Medical physics
Educational field:Medical physics
Research topic:Proton therapy


Recently, with the background of improved treatment outcomes due to the advance of medical science and engineering, the needs for radiation treatment have rapidly increased. Particularly, particle beam therapy that applies particle accelerators to medical treatment has been welcomed for its ability to minimize the physical burden on patients by concentrating the delivered doses on the cancer lesion. In addition, recent use of image-guided radiation therapy has enabled treatments that incorporate features of biological response and changes in tumor shapes and movement of patients during treatment. We have conducted research to applying radiation physics, quantum beam applied engineering, and image engineering to practical clinical settings in collaboration with the Proton Beam Therapy Center, Hokkaido University Hospital and Division of Quantum Science and Engineering, Faculty of Engineering.

Research theme

・Dual-source cone beam CT imaging on the rotating gantry of proton beam therapy system
Proton beam therapy requires highly-precise image guidance in patient setup to ensure accurate dose delivery. Cone-beam CT (CBCT) is expected to play an important role to reduce uncertainties in patient setup. However, CBCT image acquisition using gantry-mounted imaging system has some disadvantages. It has been pointed out that the scan acquisition time for CBCT imaging is long due to limited rotation speed of the gantry. This leads to prolongation of setup time and may result in degradation of patient throughput. We investigate the feasibility of fast CBCT image acquisition and 4D-CBCT reconstruction based on the 3D fiducial marker position obtained from real-time tumor tracking system using a dual-orthogonal fluoroscopic imaging system equipped on rotating gantry of proton beam therapy system.

・Knowledge-based DVH prediction method for proton therapy
Treatment planning in radiotherapy is time-consuming process and its quality relies on expertise of planner. Prediction of achievable dose volume histogram (DVH) of organ at risks (OARs) is expected to improve efficiency and quality of treatment plan. Many studies have proposed knowledge-based DVH prediction models for intensity-modulated radiotherapy (IMRT). It is unsuitable, however, to apply these prediction models to proton beam therapy (PBT), because dose distribution in PBT is strongly dependent on beam angle and weight unlike in IMRT. We have developed a knowledge-based DVH prediction model for OARs in PBT plan.

Key Publications

Research paper

  • Takao S, Miyamoto N, Matsuura T, et al., “Intrafractional baseline shift/drift of lung tumor motion during gated radiotherapy with a real-time tumor-tracking system” International Journal of Radiation Oncology* Biology* Physics, 94(1), 172–180 (2016)
  • Fujii Y, Matsuura T, Takao S, et al., “A simulation study on the dosimetric benefit of real-time motion compensation in spot-scanning proton therapy for prostate” Journal of Radiation Research, 58(4), 591-597 (2017)
  • Shirato H, Le QT, Kobashi K, Prayongrat A, Takao S, et al., “Selection of external beam radiotherapy approaches for precise and accurate cancer treatment” Journal of Radiation Research, 59(s1), i2-i10 (2018)


  • American Society for Radiation Oncology 55th Annual meeting, Basic Science Abstract Award (2013)

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