Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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The Influence of Volume Effect in 2D-array Ion Chamber on the Measurement of IMRT Dose Distribution

2차원 배열형 이온함의 부피효과가 세기조절방사선치료의 선량분포 측정에 미치는 영향

  • Kim, Sung Joon (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Lee, Seoung Jun (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Park, In Kyu (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Lee, Jeong Eun (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Park, Shin Hyung (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Seol, Ki Ho (Department of Radiation Oncology, Kyungpook National University Hospital) ;
  • Kim, Jae Chul (Department of Radiation Oncology, Kyungpook National University Hospital)
  • 김성준 (경북대학교병원 방사선종양학과) ;
  • 이승준 (경북대학교병원 방사선종양학과) ;
  • 박인규 (경북대학교병원 방사선종양학과) ;
  • 이정은 (경북대학교병원 방사선종양학과) ;
  • 박신형 (경북대학교병원 방사선종양학과) ;
  • 설기호 (경북대학교병원 방사선종양학과) ;
  • 김재철 (경북대학교병원 방사선종양학과)
  • Received : 2012.09.03
  • Accepted : 2013.02.28
  • Published : 2013.03.31
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Abstract

We evaluated the influence of volume effect on the measurement of IMRT dose distribution by comparing a 2D-array ion chamber and other dosimeters. Matrix phantom which is a 2D-array ion chamber having volume effect was compared with beam image system and film for the measurement of dose distribution. Five intensity-modulated radiation therapy plans were created using five fields in thevirtual phantom. The measured dose distribution was compared with the calculated one by radiation treatment planning system and analysis program. We evaluated the conformity of dose distribution by calculating correlation coefficients and gamma values. The highest error rate of 1.3% was associated with matrix phantom in which volume effect in small field sizes was substantial.

부피효과를 가지는 2차원 배열형 이온함으로부터 측정된 세기조절방사선치료의 선량분포와 부피효과를 가지지 않는 장치로부터 측정된 선량분포를 비교함으로써 이 효과가 측정결과에 미치는 영향에 대해 평가하였다. 조사면 크기에 따라 총 5개의 세기조절방사선치료계획을 5문 조사방식으로 가상의 팬톰에 시행하였다. 선량분포 측정은 매트릭스 팬톰, 빔 영상시스템, 필름 등 총 3가지 측정장치를 이용하였다. 측정된 값은 분석프로그램을 이용하여 전산화치료계획 시스템을 통해 획득된 선량분포와 비교하였다. 비교된 선량분포는 분석프로그램 상에서 상관계수와 감마값을 통해 측정장치의 부피효과 유무에 따른 차이를 분석한 결과 매트릭스 팬톰에서 최대 1.3% 이상으로 나타났다. 매트릭스 팬톰은 조사면의 크기가 작아질수록 내부의 이온함에 의해 부피효과가 커지게 되므로 다른 측정장치에 비해 더 큰 측정오차를 가지는 것으로 판단되었다.

Keywords

References

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