Survey and profile data on particle therapy technology in Japan.

The purpose of this study is to report profile data on the technical elements of Japanese particle therapy facilities. We requested a survey on the following four technical elements; (1) facilities and systems, (2) immobilization device and treatment planning CT, (3) patient specific QA, and (4) patient positioning. Responses were received from 21 facilities. The most commonly used accelerators were synchrotrons, which were used in 17 facilities (81.0%). The lowest available energy was widely distributed between 55.6 MeV/u and 290 MeV/u, but the maximum energy was often around 240 MeV/u for proton beams and 430 MeV for carbon ion beams. Of all treatment rooms, passive irradiation accounted for 57.7% (30 rooms), layer stacking irradiation for 7.7% (4 rooms), and scanning irradiation for 32.7% (17 rooms). Shell-type immobilization devices were most commonly used in the head and neck region, and vacuum bags were most commonly used in the thoracic to caudal regions. Lateral dose profile measurement was the most commonly used patient specific QA method. The most commonly used detector was the ionization chamber or ionization chamber-type planar detector. 2D X-ray radiography was the most commonly used in patient positioning. Marker matching was commonly used for the prostate and liver, bone matching for the head and neck and lungs, and tumor matching was used only sparingly. The results of this study may clarify current issues in particle therapy technology and provide data to guide further technology development.