Radiation Oncology Journal

The Korean Society for Radiation Oncology (대한방사선종양학회)
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Evaluation of Scatter Reduction Effect of the Aft-Multiple-Slit (AMS) System Using MC Simulation

MC 시뮬레이션을 이용한 Aft-Multiple-Silt 시스템의 산란선 제거 효과 평가

  • Chang, Jin-A (Department of Biomedical Engineering, The Catholic University of Korea School of Medicine) ;
  • Suh, Tae-Suk (Department of Biomedical Engineering, The Catholic University of Korea School of Medicine) ;
  • Jang, Doh-Yun (Department of Nuclear Engineering, Hanyang University) ;
  • Jang, Hong-Seok (Department of Radiation Oncology, Seoul St. Mary's Hospital, The Catholic University of Korea School of Medicine) ;
  • Kim, Si-Yong (Department of Radiation Oncology, Mayo Clinic)
  • 장지나 (가톨릭대학교 의과대학 의공학교실) ;
  • 서태석 (가톨릭대학교 의과대학 의공학교실) ;
  • 장도윤 (한양대학교 원자력공학과) ;
  • 장홍석 (가톨릭대학교 서울성모병원 방사선종양학과) ;
  • 김시용 (Mayo Clinic 방사선종양학회)
  • Received : 2010.06.04
  • Accepted : 2010.10.20
  • Published : 2010.12.31
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Abstract

Purpose: We designed the aft-multiple-slit (AMS) system to reduce scatter in cone-beam computed tomography (CBCT). As a preliminary study, we performed a Monte Carlo N-Particle Transport Code (MCNP) simulation to verify the effectiveness of this system. Materials and Methods: The MCNPX code was used to build the AMS geometry. An AMS is an equi-angled arc to consider beam divergence. The scatter-reduced projection images were compared with the primary images only and the primary plus scatter radiation images with and without AMS to evaluate the effectiveness of scatter reduction. To obtain the full 2 dimensional (2D) projection image, the whole AMS system was moved to obtain closed septa of the AMS after the first image acquisition. Results: The primary radiation with and without AMS is identical to all the slit widths, but the profiles of the primary plus scattered radiation varied according to the slit widths in the 2D projection image. The average scatter reduction factors were 29%, 15%, 9%, and 8% when the slit widths were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. Conclusion: We have evaluated the scatter reduction effect of the AMS in CBCT imaging using the Monte Carlo (MC) simulations. A preliminary study based on the MCNP simulations showed a mount of scatter reduction with the proposed system.

목적: 본 연구에서는 콘빔 CT에서 산란선 제거를 위한 aft-multple-slit (AMS) 시스템을 설계하였다. 예비 연구로서 본 시스템의 효용성을 검증하기 위해 MC 시뮬레이션을 수행하였다. 대상 및 방법: 가상 시뮬레이션은 산란선과 산란선+일차선을 계산할 수 있는 MCNPX의 radiography tally 5를 이용하였다. AMS는 빔의 발산성을 고려한 각이 동일한 아크 형태이고, 길이 방향에서의 산란선을 막는다. AMS의 효용성을 위한 평가는 AMS를 사용하지 않았을 때의 일차선과 산란선을 비교함으로써 수행되었다. 2D projection 영상을 얻기 위해 전체의 AMS는 한번의 캔트리 회전 후 AMS에 의해 가려진 부분의 영상 획득을 위해 다시 한 번 회전하는 구조이다. 결과: 일차선의 2D projection 영상은 모든 AMS의 폭에서 그리고 AMS를 사용하지 않았을 때에도 동일하였으나 일차선+산란선의 2D projection 영상은 slit의 폭에 따라 결과가 변했다. Slit의 폭을 5 mm, 10 mm, 15 mm, 20 mm로 하였을 때 평균 산란성 제거율은 29%, 15%, 9%, 8%였다. 결론: 본 연구에서는 AMS를 이용한 콘빔 CT의 산란선 제거 효과를 평가하였다. MC 시뮬레이션을 이용한 본 시스템의 사전 연구에서는 상당한 산란선 제거 효과를 보여주었다.

Keywords

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