Development of NIRS pencil beam scanning system for carbon ion radiotherapy

At Heavy Ion Medical Accelerator in Chiba (HIMAC) in National Institute of Radiological Sciences (NIRS), more than 9000 patients have been successfully treated by carbon ion beams since 1994. The successful results of treatments have led us to construct a new treatment facility equipped with a three-dimensional pencil beam scanning irradiation system, which is one of sophisticated techniques for cancer therapy with high energetic ion beam. This new facility comprises two treatment rooms having fixed beam lines and one treatment room having rotating gantry line. The challenge of this project is to realize treatment of a moving target by scanning irradiation. Thus, to realize this, the development of the fast scanning system is one of the most important issues in this project. After intense commissioning and quality assurance tests, the treatment with scanned ion beam was started in May 2011. After treatment of static target starts, we have developed related technologies. As a result, we can start treatment of moving target and treatment without range shifter plates since 2015. In this paper, the developments of the scanning irradiation system are described.