Journal of Radiation Protection and Research

The Korean Association for Radiation Protection (대한방사선방어학회)
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MU Fluence Reconstruction based-on Delivered Leaf Position: for IMRT Quality Assurance

세기조절방사선치료의 정도관리를 위한 모니터유닛 공간분포 재구성의 효용성 평가

  • Park, So-Yeon (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Park, Yang-Kyun (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Park, Jong-Min (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Choi, Chang-Heon (Department of Radiation Applied Life Science, Seoul National University Graduate School) ;
  • Ye, Sung-Joon (Department of Radiation Oncology, Seoul National University College of Medicine)
  • 박소연 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 박양균 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 박종민 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 최창헌 (서울대학교 대학원 방사선응용생명과학 협동과정) ;
  • 예성준 (서울대학교 의과대학 방사선종양학교실)
  • Received : 2011.02.14
  • Accepted : 2011.03.22
  • Published : 2011.03.30
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Abstract

The measurement-based verification for intensity modulated radiation therapy (IMRT) is a time-and labor-consuming procedure. Instead, this study aims to develop a MU fluence reconstruction method for IMRT QA. Total actual fluences from treatment planning system (TPS, Eclipse 8.6, Varian) were selected as a reference. Delivered leaf positions according to MU were extracted by the dynalog file generated after IMRT delivery. An in-house software was develop to reconstruct MU fluence from the acquired delivered leaf position data using MATLAB. We investigated five patient's plans delivered by both step-and-shoot IMRT and sliding window technologies. The total actual fluence was compared with the MU fluence reconstructed by using commercial software (Verisoft 3.1, PTW) and gamma analysis method (criteria: 3%/3 mm and 2%/1 mm). Gamma pass rates were $97.8{\pm}1.33$% and the reconstructed fluence was shown good agreement with RTP-based actual fluence. The fluence from step and shoot IMRT was shown slightly higher agreement with the actual fluence than that from sliding window IMRT. If moving from IMRT QA measurements toward independent computer calculations, the developed method can be used for IMRT QA. A point dose calculation method from reconstructed fluences is under development for the routine IMRT QA purpose.

세기조절방사선치료(Intensity Modulated Radiotherapy, IMRT)의 정도관리를 위해서 독립적인 방법으로 선량검증을 하는 것은 중요하다. 독립적 선량검증을 위해 팬톰과 이온전리함을 이용한 측정 방법이 보편적으로 이루어지지만 많은 시간과 노력이 요구된다. 본 연구에서는 세기조절방사선치료 시 시간에 따른 다엽콜리메이터의 움직임을 기록한 dynalog 파일을 이용하여 치료계획에서 도출된 총 실제 플루언스와 실제 치료 시의 모니터유닛(monitor unit, MU) 공간분포를 비교함으로써 간편한 세기조절방사선치료 정도관리 기술을 개발하였다. DICOM RT plan 파일로부터 총 실제 플루언스를 추출하고 MATLAB 코드를 이용하여 실제 치료 시 MU 공간분포를 dynalog 파일로부터 계산하였다. 개발된 방법의 효용성을 검증하기 위해 단계별조사기법과 동적조사기법으로 치료 받은 각 5명의 환자 데이터를 후향적으로 분석하였다. 분석 방법은 상용프로그램(Verisoft 3.1, PTW, German)에서 제공하는 감마인덱스를 사용하였다. 분석 결과 실제 치료 시의 MU 공간분포와 치료계획 상의 MU 공간분포 일치도가 평균 $97.8{\pm}1.33$%로 높은 일치도를 나타냈다. MU 공간분포 재구성의 정확도는 동적조사기법보다 단계별조사기법이 평균 1.4% 높았다. 본 연구에서 개발된 기술을 통해 세기조절방사선치료의 선량검증을 효과적으로 수행할 수 있다. 또한 분할치료 시 선량보정에 적용함으로써 맞춤형치료(adaptive radiotherapy)를 위한 기초자료로 사용될 수 있을 것이다.

Keywords

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