QST is pursuing the development of heavy particle radiotherapy using multi-ions toward the realization of a next-generation “quantum scalpel” device. The institutes have been working on its development together with Sumitomo Heavy Industries (SHI) since 2016.

In conventional heavy-particle radiotherapy equipment, only carbon ions are used. In multi-ion therapy, on the other hand, various kinds of ion beams—optimal for the specific malignancy—are combined to kill more cancer cells with fewer side effects.

In 2022, QST and SHI succeeded in creating a multi-ion source, using neon, oxygen, and helium ions among others, making multi-ion radiotherapy possible. The system was installed at QST’s Heavy Ion Medical Accelerator in Chiba (HIMAC) for further research.

With the new system, oxygen, heavier than carbon, was irradiated to the center of a tumor, and helium, lighter than carbon, was irradiated to an area nearer to normal tissue. Dose distribution and distribution of biological effects were also analyzed. Through a comparison with cases where only carbon ions were irradiated, it was confirmed that using different ion beams was more effective.

In surgical treatments for sarcoma, depending on the site of the operation, patients often experience nerve injuries (neuropathy). Satisfactory results have been obtained using heavy ions, even for those patients for whom surgery would not have been possible. Moreover, in treatments of very large tumors, recurrence has been a frequent problem.

The first case using multi-ion therapy occurred in November and December 2023, involving irradiation applied on the same patient 16 times. For the first time, carbon and oxygen irradiations were done on the same day, and switching between them was conducted smoothly. The patient was discharged the day after the treatments ended, and no early side effects were seen two months later.

For 30 years, since clinical experiments were begun in 1994, HIMAC has been a pioneer in heavy-ion radiotherapy. It has contributed to the introduction of innovative technologies and increased the availability of radiotherapy treatments, accumulating a history of positive results. It continues to be an impetus for new applications both domestically and internationally.

The development and use of a superconductive magnetic rotating gantry have enabled intensive irradiation to subject areas without the need for complex positioning beds, both improving results and reducing the burden on patients.

On February 1 of this year, HIMAC jointly won the “One Step on Electro-Technology” award, along with SHI, Toshiba Energy Systems & Solutions Corporation and Hitachi, given by the Institute of Electrical Engineers of Japan, which recognizes electrical technology making significant contributions to society. The award has been given annually for over 25 years.