Derivation of Photon Energy Fluence and Mass Energy Absorption Coefficient for 1 Gy Absorbed Dose of Water in Brachytherapy using Ir192 Source

Ir192 선원을 이용한 근접치료에서 물 흡수선량 1 Gy에 대한 광자에너지 플루언스와 질량에너지흡수계수 유도

이 연구의 목적은 Ir192 선원을 이용한 근접치료에서 물 흡수선량 1 Gy에 대한 광자 에너지플루언스와 질량에너지흡수계수를 유도하는데 있다. Khan이 저술한 방사선치료물리학으로부터 Ir192 선원의 감마선 선속에 대한 납의 반가층을 얻었다. 얻어진 납의 반가층으로부터 선감쇠계수와 질량감쇠계수를 산출하였다. 산출된 납의 질량감쇠계수를 NIST의 납의 질량감쇠계수 자료에 대응시켜 일치하는 질량감쇠계수의 광자에너지를 유효에너지로 결정하였다. 결정된 유효에너지를 NIST의 물의 질량에너지흡수계수 자료의 광자에너지에 대응시켜서, 물의 질량에너지흡수계수는 0.03273 cm2/g(32.73 cm2/kg)으로 얻었다. 얻어진 물의 질량에너지흡수계수(32.73 cm2/kg)를 물 흡수선량 1 Gy에 나누어 광자에너지플루언스는 0.03055 J/cm2으로 산출하였다.

The purpose of this study is to derive photon energy fluence and mass energy absorption coefficient for 1 Gy of absorbed dose of water in brachytherapy using an Ir192 source. From the radiotherapy physics written by Khan, the half-value of lead for the gamma ray beam of the Ir192 source was obtained. The linear attenuation coefficient and the mass attenuation coefficient were calculated from the obtained half-value layer of lead. By matching the calculated lead mass attenuation coefficient with the NIST mass attenuation coefficient data, the photon energy of the matching mass attenuation coefficient was determined as the effective energy. By matching the determined effective energy with the photon energy of the NIST data on the mass energy absorption coefficient of water, the mass energy absorption coefficient of water was obtained as 0.03273 cm2/g(32.73 cm2/kg). The photon energy fluence was calculated as 0.03055 J/cm2 by dividing the obtained mass energy absorption coefficient (32.73 cm2/kg) by the absorbed dose of water 1 Gy.