Scattered photons on inhomogeneous phantom transmission plane: an analysis based on pencil beam scatter kernels(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2020年第1期
- Page:
- 11-16
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Scattered photons on inhomogeneous phantom transmission plane: an analysis based on pencil beam scatter kernels
- Author(s):
- LIU Bote1; 2; ZHENG Huaqing1; WANG Hui1; WANG Dong1; JIA Jing1
- 1. Key Laboratory of Neutronics and Radiation Safety, Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences, Hefei 230031, China; 2. University of Science and Technology of China, Hefei 230026, China
- Keywords:
- Keywords: electronic portal imaging devices; in vivo dosimetric verification; EGSnrc simulation; transmission plane; scattered photons; pencil beam scatter kernel
- PACS:
- R318；R812
- DOI:
- DOI:10.3969/j.issn.1005-202X.2020.01.003
- Abstract:
- Objective To analyze the physical characteristics of scattered photons on transmission planes and the effects of inhomogeneous phantom thickness on scatter kernels with the use of Monte Carlo method, and to provide a basis for the studies on electronic portal imaging devices-based in vivo dosimetric verification. Methods Pencil beam scatter kernel model was established by EGSnrc. After the X-rays passing through inhomogeneous phantoms (water-lung-water phantoms and water-bone-water phantoms) and their equivalent homogeneous phantoms (EHPs), the energy fluence distributions of different scattered photons on transmission plane which was 30 cm below phantoms were obtained. The energy fluence deviation of scattered photons between inhomogeneous phantoms (water-lung-water phantoms and water-bone-water phantoms) and their EHPs were analyzed. Results The maximum energy fluence of the first order Compton scatter of scatter kernels was 1×10-4 MeV·cm-2 orders of magnitude, and fell to the half when the off-axis distance was 8 to 12 cm. For other scattered photons of scatter kernels, the maximum energy fluence was near or lower than 1×10-5 MeV·cm-2. The relative deviation of energy fluence of scatter kernels was in the range of ±1.2% to ±11.5% between inhomogeneous phantoms (water-lung-water phantoms and water-bone-water phantoms) and EHPs, and the deviation was larger with the increase of inhomogeneous phantom thickness. Conclusion The first order Compton scatter of scatter kernels accounts for the largerst and contributed to the most of the relative deviations of energy fluence. Therefore, the effect of the first order Compton scatter should be considered and corrected when reconstructing the rays on the EPID plane after the reconstruction of inhomogeneous phantom by scatter kernels.
Last Update: 2020-01-14