TITLE:
Evaluation of Patient-Specific Quality Assurance for Carbon Ion Radiotherapy Using Full Energy Scanning Method at QST Hospital
AUTHORS:
Asami Inomata, Masashi Katsumata, Sung Hyun Lee, Yui Suzuki, Takeo Nakajima, Wataru Furuichi, Keishi Yamaoka, Atsushi Yamamoto, Hideyuki Mizuno, Ryosuke Kohno
KEYWORDS:
Carbon Ion Radiotherapy, Full Energy Scanning, Patient-Specific Quality Assurance, Gamma Index
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.11 No.4,
November
30,
2022
ABSTRACT: Purpose:Patient-specific QA (PSQA) measurements for carbon ion radiotherapy (CIRT) are critical components of processes designed to identifydiscrepancies between calculated and delivered doses. We report the results of PSQA conducted at the QST Hospital during the period from September 2017 to March 2018. Methods:We analyzed PSQA results for 1448 fields for 10 disease sites with various target volumes, target depths and number of energy layers. For the PSQA, all the planned beams were recalculated on a water phantom with treatment planning software. The recalculated dose distributions were compared with the measured distributions using a 2Dionization chamber array at three depths, including 95% of the area of the prescription dose. These recalculated dose distributions were evaluated using the 3%/3mm gamma index with a passing threshold of 90%. Results:The passing rates for prostate, head and neck, and bone and soft tissue were96.8%, 99.3%, and 91.7%, respectively. Additionally, 94.7% of lung plans with low energy beams passed. Overall, the CIRT in the QST Hospital reached a high passing rate of more than 95%.Although the remaining 5% failed to pass, there was no dependence between measurement depth and disease sites in these failures. Conclusion: Using PSQA measurements, we confirmed consistency between the planned and delivered doses for CIRT using the full energy scanning method.