The Journal of Korean Society for Radiation Therapy (대한방사선치료학회지)

Korean Society for Radiation Therapy (대한방사선치료학회)
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Evaluation of usability of the shielding effect for thyroid shield for peripheral dose during whole brain radiation therapy

전뇌 방사선 치료 시 갑상선 차폐체의 주변선량 차폐효과에 대한 유용성 평가

  • Yang, Myung Sic (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) ;
  • 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)
  • 양명식 (전북대학교병원 방사선종양학과, 전북대학교 의학전문대학원 방사선종양학 교실) ;
  • 차석용 (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)
  • Received : 2014.09.30
  • Accepted : 2014.12.02
  • Published : 2014.12.30
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Abstract

Purpose : To reduce the radiation dose to the thyroid that is affected to scattered radiation, the shield was used. And we evaluated the shielding effect for the thyroid during whole brain radiation therapy. Materials and Methods : To measure the dose of the thyroid, 300cGy were delivered to the phantom using a linear accelerator(Clinac iX VARIAN, USA.)in the way of the 6MV X-ray in bilateral. To measure the entrance surface dose of the thyroid, five glass dosimeters were placed in the 10th slice's surface of the phantom with a 1.5 cm interval. The average values were calculated by measured values in five times each, using bismuth shield, 0.5 mmPb shield, self-made 1.0 mmPb shield and unshield. In the same location, to measure the depth dose of the thyroid, five glass dosimeters were placed in the 10th slice by 2.5 cm depth of the phantom with a 1.5 cm interval. The average values were calculated by measured values in five times each, using bismuth shield, 0.5 mmPb shield, self-made 1.0 mmPb shield and unshield. Results : Entrance surface dose of the thyroid were respectively 44.89 mGy at the unshield, 36.03 mGy at the bismuth shield, 31.03 mGy at the 0.5 mmPb shield and 23.21 mGy at a self-made 1.0 mmPb shield. In addition, the depth dose of the thyroid were respectively 36.10 mGy at the unshield, 34.52 mGy at the bismuth shield, 32.28 mGy at the 0.5 mmPb shield and 25.50 mGy at a self-made 1.0 mmPb shield. Conclusion : The thyroid was affected by the secondary scattering dose and leakage dose outside of the radiation field during whole brain radiation therapy. When using a shield in the thyroid, the depth dose of thyroid showed 11~30% reduction effect and the surface dose of thyroid showed 20~48% reduction effect. Therefore, by using the thyroid shield, it is considered to effectively protect the thyroid and can perform the treatment.

목 적 : 전뇌 방사선 치료 시 산란선으로 인하여 영향을 받는 갑상선의 피폭선량을 감소시키기 위해 차폐체를 사용하여 갑상선의 차폐 효과를 평가하고자 한다. 대상 및 방법 : 갑상선의 피폭선량을 측정하기 위해 선형가속기(Clinac iX. VARIAN, USA)를 이용하여 6 MV X선, 300 cGy를 인체모형팬텀에 대향 2문 조사하였다. 갑상선의 입사표면선량을 측정하기 위해 인체모형팬텀의 10번째 슬라이스 표면에 유리선량계 다섯 개를 1.5 cm 간격으로 위치시킨 후 차폐체 미사용, bismuth 차폐체 사용, 0.5 mmPb 차폐체 사용, 자체 제작한 1.0 mmPb 차폐체를 사용하여 각각 5회씩 측정하여 평균값을 산출하였다. 또한, 같은 위치에서 갑상선 심부선량을 측정하기 위해서 인체모형팬텀의 10번째 슬라이스 2.5 cm 깊이에서 유리선량계 다섯 개를 1.5 cm 간격으로 위치시킨 후 차폐체 미사용, bismuth 차폐체 사용, 0.5 mmPb 차폐체 사용, 자체 제작한 1.0 mmPb 차폐체를 사용하여 각각 5회씩 측정하여 평균값을 산출하였다. 결 과 : 갑상선의 입사표면선량은 차폐체 미사용 시 44.89 mGy로 측정되었고, bismuth 차폐체는 36.03 mGy, 0.5 mmPb 차폐체는 31.03 mGy, 자체 제작한 1.0 mmPb 차폐체는 23.21 mGy로 측정되었다. 또한, 갑상선의 심부선량은 차폐체 미사용 시 36.10 mGy로 측정되었고, bismuth 차폐체는 34.52 mGy, 0.5 mmPb 차폐체는 32.28 mGy, 자체 제작한 1.0 mmPb 차폐체는 25.50 mGy로 측정되었다. 결 론 : 전뇌 방사선 치료 시 방사선 조사면 밖의 영역에서 발생하는 이차 산란 및 누출 선량에 의해 영향을 받는 갑상선에 대하여 차폐체를 사용했을 때 갑상선 심부는 약 11~30%, 갑상선 표면은 약 20~48% 정도의 피폭선량 감소 효과가 나타났다. 따라서 전뇌 방사선 치료 시 갑상선 차폐체를 사용함으로써 갑상선을 효과적으로 보호하며 치료를 시행할 수 있을 것으로 사료된다.

Keywords

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