Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Determination of Beam Quality Correction Factors for the PTW-Markus Chamber for Electron Beam Qualities R50=1.0 and 1.4 g/cm2

전자선 선질 R50=1.0과 1.4 g/cm2에 대한 PTW-Markus 전리함의 선질보정인자 결정에 관한 연구

  • Kim, Me Young (Medical Radiation Physics Laboratory, Dongnam Institute of Radiological & Medical Sciences) ;
  • Rhee, Dong Joo (Medical Radiation Physics Laboratory, Dongnam Institute of Radiological & Medical Sciences) ;
  • Moon, Young Min (Department of Radiation Oncology, Dongnam Institute of Radiological & Medical Sciences) ;
  • Jeong, Dong Hyeok (Medical Radiation Physics Laboratory, Dongnam Institute of Radiological & Medical Sciences)
  • 김미영 (동남권원자력의학원 연구센터) ;
  • 이동주 (동남권원자력의학원 연구센터) ;
  • 문영민 (동남권원자력의학원 방사선종양학과) ;
  • 정동혁 (동남권원자력의학원 연구센터)
  • Received : 2015.09.03
  • Accepted : 2015.09.19
  • Published : 2015.09.30
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Abstract

The Markus ionization chamber(R) is a small plane parallel ionization chamber widely used in clinical electron beam dosimetry. Plane parallel chambers were recommended for low energy electron dosimetry with the beam quality at $R_{50}<4.0g/cm^2$ (${\bar{E}}{\approx}10MeV$) according to TRS-398 protocol. However, the quality correction factors ($k_{Q,Q_0}$) of the Markus chamber was not presented in TRS-398 protocol for electron beam quality at $R_{50}<2.0g/cm^2$ (${\bar{E}}{\approx}4MeV$). In this study, the $k_{Q,Q_0}$ factors of the Markus chambers (PTW-34045) for beam qualities at $R_{50}=1.0$, 1.4, 2.0, 2.5, 3.0, and $5.0g/cm^2$ were determined by Monte Carlo calculations (DOSRZnrc/EGSnrc) and the dosimetric formalism of quality correction factor. The derived $k_{Q,Q_0}$ values were evaluated using the produced data based on TRS-398 and TG-51 protocols and known values for the Markus chamber.

마커스 전리함은 치료용 전자선의 흡수선량 측정에 널리 사용되는 소형 평행 평판형 전리함이다. 특히 TRS-398 프로토콜에서는 $R_{50}<4.0g/cm^2$ (약 10 MeV 이하)에서 평행 평판형 전리함의 사용을 권고하고 있다. 그러나 TRS-398 프로토콜에서 $R_{50}<2.0g/cm^2$ (약 4 MeV 이하)에 대한 선질보정인자($k_{Q,Q_0}$)가 없어 낮은 에너지에 대한 선량측정이 필요한 경우에 마커스 전리함을 사용할 수 없다. 본 연구에서는 몬테칼로 계산(DOSRZnrc/EGSnrc)과 선량학적 계산을 이용하여 전자선 선질 $R_{50}=1.0$, 1.4, 2.0, 2.5, 3.0, $5.0g/cm^2$에 대하여 마커스 전리함(PTW-M34045)에 대한 $k_{Q,Q_0}$를 결정하였다. 본 연구에서는 결정된 $k_{Q,Q_0}$에 대해 TRS-398 및 TG-51 프로토콜의 자료와 알려진 자료들을 이용하여 평가하였다.

Keywords

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