Progress in Medical Physics (한국의학물리학회지:의학물리)

Korean Society of Medical Physics (한국의학물리학회)
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Calculation of Dose Distribution for SBRT Patient Using Geant4 Simulation Code

Geant4 전산모사 코드를 이용한 SBRT 환자의 선량분포 계산

  • Kang, Jeongku (Department of Radiation Oncology, Presbyterian Medical Center) ;
  • Lee, Jeongok (Department of Radiology, Wonkwang Health Science University) ;
  • Lee, Dong Joon (Department of Neurosurgery, Ilsan Paik Hospital, School of Medicine, Inje University)
  • 강정구 (예수병원 방사선종양학과) ;
  • 이정옥 (원광보건대학교 방사선과) ;
  • 이동준 (인제대학교 의과대학 일산백병원 신경외과학교실)
  • Received : 2015.02.25
  • Accepted : 2015.03.08
  • Published : 2015.03.31
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Abstract

The Monte Carlo based dose calculation program for stereotactic body radiotherapy was developed in this study. The Geant4 toolkit widely used in the radiotherapy was used for this study. The photon energy spectrum of the medical linac studied in the previous research was applied for the patient dose calculations. The geometry of the radiation fields defined by multi-leaf collimators were taken into account in the PrimaryGeneratorAction class of the Geant4 code. The total of 8 fields were demonstrated in the patient dose calculations, where rotation matrix as a function of gantry angle was used for the determination of the source positions. The DicomHandler class converted the binary file format of the DICOM data containing the matrix number, pixel size, endian type, HU number, bit size, padding value and high bits order to the ASCII file format. The patient phantom was constructed using the converted ASCII file. The EGSnrc code was used to compare the calculation efficiency of the material data.

정위체부방사선수술(SBRT) 환자의 선량분포를 계산하기 위해 전산모사 방식을 이용한 응용프로그램을 개발 하였다. 본 소프트웨어는 최근 이용이 활발하게 증가하고 있는 Geant4를 기반으로 개발 하였다. 환자에 조사하기 위한 광자선 스펙트럼은 이전 연구에서 구한 선형가속기 스펙트럼 자료를 사용하였다. 치료계획시스템과 유사한 조사면을 구현하기 위하여 PrimaryGeneratorAction 클래스에서 MLC 조사면 형태를 반영하도록 하였다. 본 연구에서는 8개 조사면에 대한 계산을 수행하였으며 이 때 갠트리의 각도는 PrimaryGeneratorAction 클래스에서 회전 매트릭스를 사용하여 선원의 위치를 변경하는 방법을 사용하였다. 환자에 대한 물질 자료는 CT의 dicom 파일에서 픽셀 크기, 매트릭스 크기 등의 정보와 픽셀의 HU를 밀도로 변환한 파일을 생성한 다음 이 파일을 이용 환자의 모델링에 이용 하였다. 환자의 물질 구성과 기하학적 자료의 입력에 있어 EGSnrc 코드와의 비교를 통하여 계산의 효율성을 비교하였다.

Keywords

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