Experimental investigation of the photoneutron production out of the high-energy photon fields at linear accelerator

고에너지 방사선치료 시 치료변수에 따른 광중성자 선량 변화 연구

  • Kim, Yeon Su (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Yoon, In Ha (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Bae, Sun Myeong (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Kang, Tae Young (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Baek, Geum Mun (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Kim, Sung Hwan (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Nam, Uk Won (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Lee, Jae Jin (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute) ;
  • Park, Yeong Sik (Department of Radiation Oncology, ASAN Medical Center, Department of Radiological Science, Cheongju University, Korea Astronomy and Space Science Institute)
  • 김연수 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 윤인하 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 배선명 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 강태영 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 백금문 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 김성환 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 남욱원 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 이재진 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원) ;
  • 박영식 (서울아산병원 방사선종양학과, 청주대학교 방사선학과, 한국천문연구원)
  • Received : 2014.09.30
  • Accepted : 2014.12.02
  • Published : 2014.12.30

Abstract

Purpose : Photoneutron dose in high-energy photon radiotherapy at linear accelerator increase the risk for secondary cancer. The purpose of this investigation is to evaluate the dose variation of photoneutron with different treatment method, flattening filter, dose rate and gantry angle in radiation therapy with high-energy photon beam ($E{\geq}8MeV$). Materials and Methods : TrueBeam $ST{\time}TM$(Ver1.5, Varian, USA) and Korea Tissue Equivalent Proportional Counter (KTEPC) were used to detect the photoneutron dose out of the high-energy photon field. Complex Patient plans using Eclipse planning system (Version 10.0, Varian, USA) was used to experiment with different treatment technique(IMRT, VMAT), condition of flattening filter and three different dose rate. Scattered photoneutron dose was measured at eight different gantry angles with open field (Field size : $5{\time}5cm$). Results : The mean values of the detected photoneutron dose from IMRT and VMAT were $449.7{\mu}Sv$, $2940.7{\mu}Sv$. The mean values of the detected photoneutron dose with Flattening Filter(FF) and Flattening Filter Free(FFF) were measured as $2940.7{\mu}Sv$, $232.0{\mu}Sv$. The mean values of the photoneutron dose for each test plan (case 1, case 2 and case 3) with FFF at the three different dose rate (400, 1200, 2400 MU/min) were $3242.5{\mu}Sv$, $3189.4{\mu}Sv$, $3191.2{\mu}Sv$ with case 1, $3493.2{\mu}Sv$, $3482.6{\mu}Sv$, $3477.2{\mu}Sv$ with case 2 and $4592.2{\mu}Sv$, $4580.0{\mu}Sv$, $4542.3{\mu}Sv$ with case 3, respectively. The mean values of the photoneutron dose at eight different gantry angles ($0^{\circ}$, $45^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$, $225^{\circ}$, $270^{\circ}$, $315^{\circ}$) were measured as $3.2{\mu}Sv$, $4.3{\mu}Sv$, $5.3{\mu}Sv$, $11.3{\mu}Sv$, $14.7{\mu}Sv$, $11.2{\mu}Sv$, $3.7{\mu}Sv$, $3.0{\mu}Sv$ at 10MV and as $373.7{\mu}Sv$, $369.6{\mu}Sv$, $384.4{\mu}Sv$, $423.6{\mu}Sv$, $447.1{\mu}Sv$, $448.0{\mu}Sv$, $384.5{\mu}Sv$, $377.3{\mu}Sv$ at 15MV. Conclusion : As a result, it is possible to reduce photoneutron dose using FFF mode and VMAT method with TrueBeam $ST{\time}TM$. The risk for secondary cancer of the patients will be decreased with continuous evaluation of the photoneutron dose.

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