Consequences of removing the flattening filter from linear accelerators in generating high dose rate photon beams for clinical applications: A Monte Carlo study verified by measurement
- 作者：E. Ishmael Parsai ; David Pearson ; Thomas Kvale
- 关键词：Monte Carlo simulation ; Flattening filter ; Linear accelerator ; IMRT
- 刊名：Nuclear Instruments and Methods in Physics Research Section B ; Beam Interactions with Materials and Atoms
- 出版年：2007
- 期刊代码：42_0168583x
- 类别：ph
- 出版时间：August 2007
- 卷：261
- 期：1-2
- 页码：755-759
- 文件大小：221 K
摘要
An Elekta SL-25 medical linear accelerator (Elekta Oncology Systems, Crawley, UK) has been modelled using Monte Carlo simulations with the photon flattening filter removed. It is hypothesized that intensity modulated radiation therapy (IMRT) treatments may be carried out after the removal of this component despite it’s criticality to standard treatments. Measurements using a scanning water phantom were also performed after the flattening filter had been removed. Both simulated and measured beam profiles showed that dose on the central axis increased, with the Monte Carlo simulations showing an increase by a factor of 2.35 for 6 MV and 4.18 for 10 MV beams. A further consequence of removing the flattening filter was the softening of the photon energy spectrum leading to a steeper reduction in dose at depths greater than the depth of maximum dose. A comparison of the points at the field edge showed that dose was reduced at these points by as much as 5.8%for larger fields. In conclusion, the greater photon fluence is expected to result in shorter treatment times, while the reduction in dose outside of the treatment field is strongly suggestive of more accurate dose delivery to the target.