Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Implementation and Evaluation of the Electron Arc Plan on a Commercial Treatment Planning System with a Pencil Beam Algorithm

Pencil Beam 알고리즘 기반의 상용 치료계획 시스템을 이용한 전자선 회전 치료 계획의 구현 및 정확도 평가

  • Kang, Sei-Kwon (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Park, So-Ah (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Hwang, Tae-Jin (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Cheong, Kwang-Ho (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Lee, Me-Yeon (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Kim, Kyoung-Ju (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Oh, Do-Hoon (Department of Radiation Oncology, Hallym University College of Medicine) ;
  • Bae, Hoon-Sik (Department of Radiation Oncology, Hallym University College of Medicine)
  • 강세권 (한림대학교 의과대학 방사선종양학교실) ;
  • 박소아 (한림대학교 의과대학 방사선종양학교실) ;
  • 황태진 (한림대학교 의과대학 방사선종양학교실) ;
  • 정광호 (한림대학교 의과대학 방사선종양학교실) ;
  • 이미연 (한림대학교 의과대학 방사선종양학교실) ;
  • 김경주 (한림대학교 의과대학 방사선종양학교실) ;
  • 오도훈 (한림대학교 의과대학 방사선종양학교실) ;
  • 배훈식 (한림대학교 의과대학 방사선종양학교실)
  • Received : 2010.06.04
  • Accepted : 2010.07.13
  • Published : 2010.09.30
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Abstract

Less execution of the electron arc treatment could in large part be attributed to the lack of an adequate planning system. Unlike most linear accelerators providing the electron arc mode, no commercial planning systems for the electron arc plan are available at this time. In this work, with the expectation that an easily accessible planning system could promote electron arc therapy, a commercial planning system was commissioned and evaluated for the electron arc plan. For the electron arc plan with use of a Varian 21-EX, Pinnacle3 (ver. 7.4f), with an electron pencil beam algorithm, was commissioned in which the arc consisted of multiple static fields with a fixed beam opening. Film dosimetry and point measurements were executed for the evaluation of the computation. Beam modeling was not satisfactory with the calculation of lateral profiles. Contrary to good agreement within 1% of the calculated and measured depth profiles, the calculated lateral profiles showed underestimation compared with measurements, such that the distance-to-agreement (DTA) was 5.1 mm at a 50% dose level for 6 MeV and 6.7 mm for 12 MeV with similar results for the measured depths. Point and film measurements for the humanoid phantom revealed that the delivered dose was more than the calculation by approximately 10%. The electron arc plan, based on the pencil beam algorithm, provides qualitative information for the dose distribution. Dose verification before the treatment should be mandatory.

현재 이용되고 있는 상용 치료 계획시스템은 대부분의 치료용 선형가속기가 제공하는 전자선 회전 방식의 치료 기능을 제공하지 않고 있으며, 이것은 전자선 회전 치료가 널리 이용되지 못하는 한 가지 원인이 되기도 한다. 본 연구에서는 Varian 21-EX에 대해, pencil beam 기반의 Pinnacle3 (ver. 7.4f)를 이용한 전자선 회전 치료를 위한 커미셔닝을 한 후, 치료 계획을 세웠으며, 그 정확도를 평가해 보았다. 회전 빔은 폭이 일정한 조사빔을 규칙적으로 반복해서 구현하였으며, 필름과 점 선량을 측정하였다. 치료계획 시스템의 모델링 단계에서, 측정된 깊이 선량분포는 모델링의 계산과 1% 내에서 일치하였으나, 가로 선량분포의 경우에는 모델링 계산이 측정보다 작아서, 50% 선량값을 기준으로 할 때, 6 MeV는 distance-to-agreement (DTA) 값이 5.1 mm, 12 MeV의 경우에는 6.7 mm이었다. 인체모형 팬텀을 대상으로한 점 선량 및 필름 측정의 경우, 계산과 측정은 10% 이상의 차이를 보였다. Pencil beam 기반의 전자선 회전 치료 계획은 정량적인 기준으로 삼기에는 부족해서 선량 분포에 대한 정성적인 참고에만 머물러야 하며, 환자 치료 전에 측정을 통해 선량 확인이 필요하다.

Keywords

References

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