Department of Accelerator and Medical Physics are operating and improving a synchrotron accelerator for heavy-ion cancer therapy, a cyclotron accelerator that produces radioisotopes for the diagnosis and treatment of cancer and dementia, and an electrostatic accelerator for PIXE elemental analysis and a microbeam cell irradiation. We are also conducting research and developments of medical physics, radiation biology, and accelerator science using these accelerators. The developed technologies are helping improve people's lives in fields such as medicine.
Research Theme
Heavy-ion Medical Accelerator, HIMAC and Heavy-ion Radiotherapy System
HIMAC (Heavy Ion Medical Accelerator in Chiba) consists of a synchrotron accelerator for accelerating heavy-ion beams, including carbon-ions, to an energy of 800 MeV per nucleon, and a treatment room for irradiating patients. The treatment room is equipped with a rotating gantry that can irradiate the patient with carbon-ion beams from any angle of 360 degrees using superconducting technology. A high-speed three-dimensional scanning device that can irradiate complex-shaped tumors in a short time is also installed. Both are aiming to reduce the physical burden on the patient and improve the treatment effect 1) 2).
Left: Schematic drawing of HIMAC, Right: Treatment Room G with rotating gantry
Developments of Image-guided and Adaptive Radiotherapy Technology
In the treatment room, we have established real-time image guided radiotherapy, including respiratory-gated irradiation. In recent years, medical staff are increasingly required to make difficult decisions as treatment techniques become more precise. Therefore, we are working on the development of image guided radiotherapy based on the AI learning from a huge number of medical images and clinical experiences. This brings us closer to realization of adaptive therapy3).
Markerless motion tracking treatment using X-ray fluoroscopy.
Development of Multi-ion Radiotherapy Technology
Heavy-ions such as carbon-ions used in radiotherapy can put a large amount of energy to cell nuclei with a single collision. Linear energy transfer (LET) is a quantity that indicates its strength and strongly influences the cell killing effect. To further enhance the therapeutic effect of carbon-ion radiotherapy, we are developing a treatment planning technology called "LET painting" that actively controls LET distribution. Furthermore, although there is a limit of the LET value by LET painting, the range of LET is greatly expanded by combining beams of multiple ion species (multi-ions). It enables heavy-ion radiotherapy that optimizes not only the dose distribution but also the LET distribution4).
Dose distribution chart (a, c, e) and LET distribution chart (b, d, f) of three cases of multi-ion radiotherapy for prostate cancer. The plan1 sets the target LET to 50 keV/mm. The plan2 further sets the rectal LET to <30 keV/mm. The plan3 further sets the prostate LET to 80 keV/mm.
Development of Next-generation Heavy-ion Radiotherapy System (Quantum Scalpel)
To reduce the size and improve the performance of heavy-ion radiotherapy system, we are conducting research and development of a next-generation heavy ion radiotherapy system consisting of a multiple-ion source, a compact linear accelerator, a superconducting synchrotron, and a superconducting rotating gantry5). The synchrotron uses a superconducting electromagnet to reduce the area to about 1/17 that of HIMAC. In addition, the multiple-ion source can output multiple highly charged ions from helium to neon and can switch ion species within one minute.
Schematic view of the next-generation heavy-ion radiotherapy system (4th generation Quantum Scalpel)
Development of irradiation and analysis technology using electrostatic accelerator
In the tandem electrostatic accelerator, PIXE (Particle Induced X-ray Emission) elemental analysis and a single cell irradiation facility by Proton/Helium microbeam (SPICE; Single Particle Eradiation for Cell) are operated. We are developing new technologies and put into practical use based on requests from users. For example, the range of analyzed elements by PIXE has been covered from Oxygen, Fluorine to Uranium. The speed and the area of cell irradiation also has been improved and the microbeam with the beam size of 2 mm can irradiate 10,000 cells per dish. The number of users from domestic and overseas universities and research institutes has increased in recent years. This facility will continue to actively engage in new technology development and research support that will contribute to the development of science.
SPICE, Microbeam Cell Irradiation Facility
Example of PIXE Analysis (NIST SRM2783)
Technology developments on cyclotron accelerators
Two cyclotrons are used for production of radioactive isotopes (RI) and for basic research in the fields of physics and biology. In RI production, in addition to RI for molecular imaging used in the diagnosis of cancer and dementia, RI for targeted radionuclide therapy is produced for drug discovery research. A stable supply of high-quality, high-intensity beams is required to produce a various kind and a sufficient amount of RI. Therefore, we are conducting research such as the development of techniques for increasing the intensity of beams, irradiation of high-intensity beams, and diagnostic techniques.
Left: Two cyclotron accelerators, Right: Target systems for RI production
References
1) Iwata Y et al., Physical Review ST-AB, 15, 044701 (2012).
2) Furukawa T et al., et al., Medical Physics, 37, 4874 (2010).
3) Mori S et al., International Journal of Radiation Oncology* Biology* Physics, 95, 258 (2016).
Research Group
- Advanced Particle Therapy System Research Group
- Therapeutic Beam Research Group
- Treatment System Research Group
- Radiation Effect Research Group
- Beam Delivery System Research Group
- HIMAC Operation Section
- Cyclotron Operation Section
- Electrostatic Accelerator Operation Section