A Study on effects of MRI magnetic field on dose distribution during MRI guided Heavy Ion Therapy

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K07743
• 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: Yamagata University
• Principal Investigator: IWAI TAKEO 山形大学, 医学部, 教授 (30272529)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 重粒子線治療 / 炭素線治療 / 核磁気共鳴画像誘導 / モンテカルロシミュレーション / 二次粒子 / 線量分布

Outline of Final Research Achievements

In order to develop carbon ion radiotherapy (CIRT) into a more powerful treatment, we conducted a particle simulation study to realize CIRT under MRI guidance. As for the magnetic field level of the MRI to be used, in addition to the general MRI magnetic field of 3T and 1.5T, the open type 0.3T, and the ultra-low magnetic field of 0.055T, which is being developed in recent years, the main magnetic field for each clarified the effect of the radiation on the dose distribution. Secondary electrons and secondary protons have little effect on the dose distribution. Although the beam is shifted by the magnetic field at the end, the shape of the lateral dose distribution is barely affected. Since the amount of shift is very small if the magnetic field is as low as ultra-low field MRI, the feasibility is high in terms of compatibility with existing facilities.

Free Research Field

医学物理学

Academic Significance and Societal Importance of the Research Achievements

重粒子線治療は、本邦で年間5000人程度が受けている最先端治療であるが、画像誘導という点では光子線治療などに後れを取っている現状である。本研究は、MRIの磁場が一次炭素線二次粒子、線量分布に与える影響を初めて明らかにした学術的意義は大きい。
光子線治療では既に臨床投入されているMRI誘導が重粒子線治療にも適用されれば、重粒子線治療の精度と信頼性が著しく向上し、適用部位や照射回数減など、さまざまなメリットがもたらされ、究極のがん治療法として社会に与えるインパクトは計り知れない。