Development of a CT number calibration audit system in radiation therapy

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K17269
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 52040:Radiological sciences-related
• Research Institution: Hiroshima University
• Principal Investigator: Nakao Minoru 広島大学, 医系科学研究科(医), 特任助教 (50726601)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 放射線治療 / 不均質補正 / 品質管理 / 第三者評価

Outline of Final Research Achievements

We developed a CT number calibration audit system in photon radiation therapy. We created the postal audit phantom and developed a software to convert CT number to mass density or relative electron density with stoichiometric CT number calibration. A new stoichiometric CT number calibration model were developed to harmonize the calculated CT number with the measured CT number for air and lung tissue. In addition, we established tolerance levels for tissue inhomogeneity corrections. Finally, we demonstrated that the new stoichiometric CT number calibration model better than conventional model through a multi-institutional study.

Free Research Field

放射線治療

Academic Significance and Societal Importance of the Research Achievements

国民が質の高い放射線治療を受けるために, 放射線治療技術の均てん化が課題となっている. 放射線治療計画装置の不均質補正に対する第三者評価方法として, ①ファントムのCT撮影, ②CT値から密度への変換, ③線量分布計算までのEnd to End試験が実施されている. 本研究によって, ③線量分布計算の影響を含まない評価法が開発されたため, End to End試験の各過程に対する個別の評価が可能となり, 各地域にある放射線治療装置の第三者評価を通して, 国民に対しより高精度な放射線治療を提供することに繋がる.