A Monte Carlo study of the variation of electron fluence in water from a 6 MV photon beam outside of the field

被引:30
作者
Kirkby, C. [1 ]
Field, C. [1 ]
MacKenzie, M. [1 ]
Syme, A. [1 ]
Fallone, B. G. [1 ]
机构
[1] Univ Alberta, Dept Med Phys, Cross Canc Ctr, Edmonton, AB T6G 1Z2, Canada
关键词
D O I
10.1088/0031-9155/52/12/015
中图分类号
R318 [生物医学工程];
学科分类号
0831 ;
摘要
Existing studies have suggested some debate on whether the quality of radiation that delivers dose outside of the primary field of a radiotherapy photon beam can be considered the same as that inside the primary field. We used a Monte Carlo approach to simulate the electron fluence differential in energy inside a water phantom in response to irradiation by a 6 MV photon beam. The goal was to quantify how significantly the electron fluence changes when moving from a volume exposed to the primary field to one outside of the primary field, and understand any potential biological implications. We scored the electron fluence outwards in annular volumes in response to a 5 cm radius 6 MV beam and at the central axis in response to a rectangular 6 MV beam partially blocked by an MLC. The resulting fluence spectra were compared to different low-LET sources for which biological response in the form of chromosomal aberrations has been published. Our results show a significant increase in the low energy component of the fluence spectra outside of the primary field, which increases the mean LET to values similar to that seen in response to a Cs-137 photon source. In turn, it is shown that this has the potential to increase the RBE.
引用
收藏
页码:3563 / 3578
页数:16
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