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  • [Sci Rep.] Compact bunker shielding assessment for 1.5 T MR-Linac

    [Sci Rep.] Compact bunker shielding assessment for 1.5 T MR-Linac

    연세의대 / 성지원, 이호*

  • 출처
    Sci Rep.
  • 등재일
    2022 Apr 25
  • 저널이슈번호
    12(1):6712. doi: 10.1038/s41598-022-10498-0.
  • 내용

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    Abstract
    This study evaluated the effect of the 1.5 T magnetic field of the magnetic resonance-guided linear accelerator (MR-Linac) on the radiation leakage doses penetrating the bunker radiation shielding wall. The evaluated 1.5 T MR-Linac Unity system has a bunker of the minimum recommended size. Unlike a conventional Linac, both primary beam transmission and secondary beam leakage were considered independently in the design and defined at the machine boundary away from the isocenter. Moreover, additional shielding was designed considering the numerous ducts between the treatment room and other rooms. The Linac shielding was evaluated by measuring the leakage doses at several locations. The intrinsic vibration and magnetic field were inspected at the proposed isocenter of the system. For verification, leakage doses were measured before and after applying the magnetic field. The intrinsic vibration and magnetic field readings were below the permitted limit. The leakage dose (0.05-12.2 µSv/week) also complied with internationally stipulated limits. The special shielding achieved a five-fold reduction in leakage dose. Applying the magnetic field increased the leakage dose by 0.12 to 4.56 µSv/week in several measurement points, although these values fall within experimental uncertainty. Thus, the effect of the magnetic field on the leakage dose could not be ascertained.

     

     

     

    Affiliations

    Jiwon Sung  1 , Yeonho Choi  2 , Jun Won Kim  1 , Ik Jae Lee  1 , Ho Lee  3
    1 Department of Radiation Oncology, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea.
    2 Department of Radiation Oncology, Gangnam Severance Hospital, 211 Eonju-ro, Gangnam-gu, Seoul, 06273, South Korea.
    3 Department of Radiation Oncology, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722, South Korea. holee@yuhs.ac.

  • 연구소개
    국내 최초로 강남세브란스병원에 도입된 Unity는 1.5T MRI와 LINAC이 융합되어 MR영상유도방사선치료를 수행하는 방사선치료기이다. Unity는 일반방사선치료기와 다른 하드웨어 구성을 가지고 있을 뿐만 아니라 빔 특징도 1.5 T 자기장 영향으로 인해 다르게 나타난다. MR-linac의 특성을 반영한 다양한 프로토콜이 발표되고 있지만 아직 차폐 설계 프로토콜 및 기준이 발표되지 않았으며 1.5T 자기장이 누설선량에 미치는 영향을 평가한 연구결과도 보고되지 않았다. 따라서 본 연구는 제조사에서 제안한 방법으로 차폐 시스템을 도입하고 1.5T 자기장 유무에 따른 누설 선량 영향 정도를 평가하였다.
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