The simple calculation method of the tissue absorbed dose in medical exposure management of X ray CT examination

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K08058
• 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: Teikyo University
• Principal Investigator: OHTANI Hiroki 帝京大学, 医療技術学部, 教授 (10259145)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: CTDIvol / DRL / X線CT / 組織吸収線量 / 実効線量 / 電離箱線量計 / 半導体検出器 / 蛍光ガラス線量計

Outline of Final Research Achievements

CTDIvol when performing CT irradiation by tube voltage 100 kV was calculated in 2020. It measured by each thickness of the phantom using the ion-chamber dosimeter. As a result, whenever phantom thickness increased both voltage, CTDIvol decreased. The ion chamber for X-rays CT was inserted into the phantom for CTDIvol measurement, and CTDIvol was measured in 2021. Radiation dosimetry of a 0.6 ml ion chamber and the semiconductor detector was installed and carried out to the phantom surface. As a result, CTDIvol changed with setup of photography conditions. In the calibration value, those who use an ion chamber rather than a semiconductor detector approached 1.0. The glass dosimeter was installed on both eye pits using the head phantom, and the tissue absorbed dose in each base line was measured in 2022. As a result, compared with OM line, the dose has been reduced about 39% by taking a photograph with a base line SM line.

Free Research Field

放射線計測学

Academic Significance and Societal Importance of the Research Achievements

学術的意義として、X線CT装置に表示されるCTDIvolと実測値の差は患者の体格によって変化することが示され、管電圧の違いでも変化が現れたことは患者ごとの線量変化において重要なデータとなった。半導体検出器を用いた表面での線量測定は患者ごとのDRLを算出する新たな手法となった。組織吸収線量として水晶体の線量がガラス線量計を用いて算出できたことにより医療被ばく線量算出が患者ごとに簡便に行われることになり、さらに組織加重係数を乗じることで実効線量が求められ被ばく低減の方法として重要なこととなった。このように社会的に関心が高い医療放射線被ばくについて理解を得る一助となったことは社会的意義が大きい。