The Evaluation of Radiation Dose to Embryo/Fetus and the Design of Shielding in the Treatment of Brain Tumors

임산부의 전뇌 방사선 치료에 있어서의 태아의 방사선량 측정 및 차폐 구조의 설계

  • Cho, Woong (Department of Radiation Oncology, Seoul National University College of Medicine) ;
  • Huh, Soon-Nyung (Department of Radiation Oncology, Seoul National University Hospital) ;
  • Chie, Eui-Kyu (Department of Radiation Oncology, Seoul National University College of Medicine, Department of Radiation Oncology, Seoul National University Hospital) ;
  • Ha, Sung-Whan (Department of Radiation Oncology, Seoul National University College of Medicine, Department of Radiation Oncology, Seoul National University Hospital) ;
  • Park, Yang-Gyun (Department of Radiation Oncology, Seoul National University College of Medicine) ;
  • Park, Jong-Min (Department of Radiation Oncology, Seoul National University College of Medicine) ;
  • Park, Suk-Won (Department of Radiology, Chung-Ang University College of Medicine)
  • 조웅 (서울대학교 의과대학 방사선 종양학교실) ;
  • 허순녕 (서울대학교 병원 치료방사선과) ;
  • 지의규 (서울대학교 의과대학 방사선 종양학교실, 서울대학교 병원 치료방사선과) ;
  • 하성환 (서울대학교 의과대학 방사선 종양학교실, 서울대학교 병원 치료방사선과) ;
  • 박양균 (서울대학교 의과대학 방사선 종양학교실) ;
  • 박종민 (서울대학교 의과대학 방사선 종양학교실) ;
  • 박석원 (중앙대학교 의과대학 방사선과학교실)
  • Published : 2006.12.30

Abstract

Purpose : To estimate the dose to the embryo/fetus of a pregnant patient with brain tumors, and to design an shielding device to keep the embryo/fetus dose under acceptable levels Materials and Methods : A shielding wall with the dimension of 1.55 m height, 0.9 m width, and 30 m thickness is fabricated with 4 trolleys under the wall. It is placed between a Patient and the treatment head of a linear accelerator to attenuate the leakage radiation effectively from the treatment head, and is placed 1 cm below the lower margin of the treatment field in order to minimize the dose to a patient from the treatment head. An anti-patient scattering neck supporters with 2 cm thick Cerrobend metal is designed to minimize the scattered radiation from the treatment fields, and it is divided into 2 section. They are installed around the patient neck by attach from right and left sides. A shielding bridge for anti-room scattered radiation is utilized to place 2 sheets of 3 mm lead plates above the abdomen to setup three detectors under the lead sheets. Humanoid phantom is irradiated with the same treatment parameters, and with and without shielding devices using TLD, and ionization chambers with and without a build-up cap. Results : The dose to the embryo/fetus without shielding was 3.20, 3.21, 1.44, 0.90 cGy at off-field distances of 30, 40, 50, and 60 cm. With shielding, the dose to embryo/fetus was reduced to 0.88, 0.60, 0.35, 0.25 cGy, and the ratio of the shielding effect varied from 70% to 80%. TLD results were 1.8, 1.2, 0.8, 1.2, and 0.8 cGy. The dose measured by the survey meter was 10.9 mR/h at the patient's surface of abdomen. The dose to the embryo/fetus was estimated to be about 1 cGy during the entire treatment. Conclusion : According to the AAPM Report No 50 regarding the dose limit of the embryo/fetus during the pregnancy, the dose to the embryo/fetus with little risk is less than 5 cGy. Our measurements satisfy the recommended values. Our shielding technique was proven to be acceptable.

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