Development of an Adaptive Patient Positioning System Based on Dose Matching for Particle Radiotherapy

2024 Fiscal Year Final Research Report

• Project/Area Number: 20K08151
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 52040:Radiological sciences-related
• Research Institution: Kanagawa Cancer Center Research Institute
• Principal Investigator: Kusano Yohsuke 地方独立行政法人神奈川県立病院機構神奈川県立がんセンター(臨床研究所), その他部局等, その他 (40619665)
• Project Period (FY): 2020-04-01 – 2025-03-31
• Keywords: 膵臓がん / coverage / 消化管ガス / 腫瘍の位置変化 / 患者位置決めソフトウェア / robust planning / target matching / dose matching

Outline of Final Research Achievements

Although particle radiotherapy creates a sharp dose distribution (Bragg peak), inaccurate irradiation positioning may reduce the tumor dose as well as cause the delivery of an unexpectedly high dose to the organs at risk. In patient positioning, bone matching cannot account for interfractional motions of tumors and organs. The tumor matching cannot account for range variations due to changes in the body, such as gastrointestinal gases and changes in bone positions. In this study, we investigated dose matching, which allows to determine the best irradiation positioning including changes in the body. The dose matching determines the irradiation position using the dose distribution. The results showed improved tumor dose in dose matching compared with bone matching and tumor matching. In addition to establishing the dose matching, this study established a robust treatment planning methodology for gastrointestinal gas, tumor growth, and the rapid change in CT values.

Free Research Field

Medical physics

Academic Significance and Societal Importance of the Research Achievements

粒子線は急峻な線量分布を描く放射線であり、正常臓器の線量を低く抑え腫瘍へ線量を集中できる。炭素線は低酸素状態の細胞へも高い殺傷能力を有し、その効果は通常のX線と比べて約3倍となる。そのため、X線が効きにくい骨軟部腫瘍や難治がんとして知られる膵臓がんへの治療効果の期待は高い。この様に高い細胞殺傷能力を持つ炭素線だが、ビーム進行方向の密度変化に弱く停止位置が変化する。日々、腫瘍や正常臓器の位置も変化する。線量集中性が良く細胞殺傷能力が高いことから、照射位置のズレは腫瘍線量の低下や正常臓器の有害事象を引き起こす。故に、正確な照射が求められる。本研究での成果は高精度照射を実現するための技術である。