Current status of East Japan Heavy Ion Center, Faculty of Medicine, Yamagata University (5)

In 2017, the Yamagata University Faculty of Medicine started a heavy ion radiotherapy facility construction project, and in February 2021, it began treating prostate cancer with a horizontal beam. After that, in May 2022, we started treating head and neck cancer using a rotating gantry, and in October 2022, we were able to treat all target areas except the eyeball. A fixed irradiation room with only a horizontal port is used for treatment of prostate cancer. With around 30 irradiations per day, the number of patients who have already completed treatment has exceeded 800. Until April 2023, it was operating without any major problems, but at the end of April 2023, the scanning magnet broke down, and the horizontal port was forced to stop operation for seven weeks. In the rotating gantry irradiation room, the beam is adjusted for each gantry angle, and the treatment area is increased while increasing the usable angle. Currently, it is possible to set the beam introduction angle in increments of 15 degrees. In the future, we will continue to re-adjust the beam transport system on the upstream side of the gantry and make angle interpolation work to further increase the angles that can be used for treatment. (author)