대한방사선치료학회지 (The Journal of Korean Society for Radiation Therapy)

대한방사선치료학회 (Korean Society for Radiation Therapy)
권호 표지

동적 세기조절방사선 치료 시 선량률 변화에 따른 선량학적엽간격 변화 분석

Analysis of dosimetric leaf gap variation on dose rate variation for dynamic IMRT

  • 양명식 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 박주경 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 이승훈 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 김양수 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 이선영 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 차석용 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실)
  • Yang, Myung Sic (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School) ;
  • Park, Ju Kyeong (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School) ;
  • Lee, Seung Hun (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School) ;
  • Kim, Yang Su (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School) ;
  • Lee, Sun Young (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School) ;
  • Cha, Seok Yong (Department of Radiation Oncology, Chonbuk National University Hospital, Department of Radiation Oncology, Chonbuk National University Medical School)
  • 투고 : 2016.05.27
  • 심사 : 2016.06.23
  • 발행 : 2016.06.30
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초록

동적 세기조절방사선치료 시 선량률 변화에 따른 다엽콜리메이터의 엽의 위치를 반영하는 선량학적엽간격과 다엽콜리메이터 투과계수 변화를 분석하여 다엽콜리메이터의 정확성을 평가하고자 하였다. Millennium 120 MLC 시스템이 장착된 선형가속기의 6 MV와 10 MV X선으로 물 팬텀의 깊이 10 cm에서 CC13과 FC-65G 전리함을 이용하여 선량률을 200, 300, 400, 500, 600 MU/min으로 변화시켜 선량학적엽간격과 다엽콜리메이터 투과계수를 측정하였다. 400 MU/min의 선량률 기준으로 200, 300, 400, 500, 600 MU/min으로 선량률을 변경하여 선량학적엽간격 값을 측정한 결과, 6 MV의 경우 각각 -2.59, -1.89, 0.00, -0.58, -2.89%의 차이가 나타났고, 10 MV에서는 각각 ?2.52, -1.69, 0.00, +1.28, -1.98%의 차이가 나타났다. 다엽콜리메이터 투과계수는 두 종류의 에너지와 모든 선량률에서 약 ${\pm}1%$ 이내의 범위로 측정되었다. 본 연구는 동적 세기조절방사선치료 시 선량률 변화에 대하여 다엽콜리메이터의 선량학적엽간격과 투과계수 변화를 평가하였다. 선량률 변화에 따라서 다엽콜리메이터의 투과계수의 차이는 미미했지만, 선량학적엽간격의 차이는 큰 것으로 확인하였다. 따라서 동적 세기조절방사선치료 시 임의로 선량률을 변경하면 종양에 전달되는 선량에 많은 영향을 미치므로 치료 중에 선량률을 변화시키지 않는 것이 더욱 정확한 방사선치료 방법이라 사료된다.

To evaluate the position accuracy of the MLC. This study analyzed the variations of the dosimetric leaf gap(DLG) and MLC transmission factor to reflect the location of the MLC leaves according to the dose rate variation for dynamic IMRT. We used the 6 MV and 10 MV X-ray beams from linear accelerator with a Millennium 120 MLC system. We measured the variation of DLG and MLC transmission factor at depth of 10 cm for the water phantom by varying the dose rate to 200, 300, 400, 500 and 600 MU/min using the CC13 and FC-65G chambers. For 6 MV X-ray beam, a result of measuring based on a dose rate 400 MU/min by varying the dose rate to 200, 300, 400, 500 and 600 MU/min of the difference rate was respectively -2.59, -1.89, 0.00, -0.58, -2.89%. For 10 MV X-ray beam, the difference rate was respectively ?2.52, -1.69, 0.00, +1.28, -1.98%. The difference rate of MLC transmission factor was in the range of about ${\pm}1%$ of the measured values at the two types of energy and all of the dose rates. This study evaluated the variation of DLG and MLC transmission factor for the dose rate variation for dynamic IMRT. The difference of the MLC transmission factor according to the dose rate variation is negligible, but, the difference of the DLG was found to be large. Therefore, when randomly changing the dose rate dynamic IMRT, it may significantly affect the dose delivered to the tumor. Unless you change the dose rate during dynamic IMRT, it is thought that is to be the more accurate radiation therapy.

키워드

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