Establishment of new reference dosimetry and international standard in MR-Linac

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K17273
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 52040:Radiological sciences-related
• Research Institution: Kumamoto University
• Principal Investigator: Ono Takeshi 熊本大学, 大学院生命科学研究部(保), 准教授 (20646971)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: MRリニアック / 電離箱線量計 / 蛍光ガラス線量計 / モンテカルロシミュレーション / Electron return effect / Electron foucsing effect

Outline of Final Research Achievements

The beam data of the MR linac modeling produced in this study showed good agreement with the values reported in previous studies. The sensitivity of the ionization chamber increased with the perpendicular static magnetic field, and the sensitivity increase was larger for larger sensitive volumes. Therefore, the use of ionization chamber with a small sensitive volume is recommended for dosimetry in the perpendicular static magnetic field. The sensitivity of the radiophotoluminescent glass dosimeter varied greatly depending on the orientation of the dosimeter and the air in the holder. However, the sensitivity change of the radiophotoluminescent glass dosimeter can be reduced. Therefore, the radiophotoluminescent glass dosimeter have the potential to be used for dosimetry without any correction for the effects of static magnetic fields, and are expected to be applied to reference dosimetry and third-party dosimetry audits.

Free Research Field

放射線計測

Academic Significance and Societal Importance of the Research Achievements

本研究により，垂直静磁場下における電離箱線量計および蛍光ガラス線量計の感度変化が明らかになった．また，静磁場における体内線量分布の変化が明らかになった．本研究の成果から，静磁場やMR造影剤を利用した新たな高精度放射線治療の開発が期待される．また，MRリニアックにおける新たな吸収線量計測法が確立され，蛍光ガラス線量計を用いたMRリニアックの線量標準の確立の可能性が示された．とくに，蛍光ガラス線量計は国産の線量計でありながら，海外の同様の線量計と比較しても，静磁場下における線量計測において，良好な特性を示しており，今後のMRリニアックの普及に伴い，国内外でのさらなる活用が期待される．