Radiation Physics, Skåne University Hospital and Lund University, Lund, Sweden.
Phys Med Biol. 2010 Dec 7;55(23):7333-44. doi: 10.1088/0031-9155/55/23/010. Epub 2010 Nov 16.
A Monte Carlo model of an Elekta Precise linear accelerator has been built and verified by measured data for a 6 and 10 MV photon beam running with and without a flattening filter in the beam line. In this study the flattening filter was replaced with a 6 mm thick copper plate, provided by the linac vendor, in order to stabilize the beam. Several studies have shown that removal of the filter improves some properties of the photon beam, which could be beneficial for radiotherapy treatments. The investigated characteristics of this new beam included output, spectra, mean energy, half value layer and the origin of scattered photons. The results showed an increased dose output per initial electron at the central axis of 1.76 and 2.66 for the 6 and 10 MV beams, respectively. The number of scattered photons from the accelerator head was reduced by (31.7 ± 0.03)% (1 SD) for the 6 MV beam and (47.6 ± 0.02)% for the 10 MV beam. The photon energy spectrum of the unflattened beam was softer compared to a conventional beam and did not vary significantly with the off-axis distance, even for the largest field size (0-20 cm off-axis).
已经建立了 Elekta 精确直线加速器的蒙特卡罗模型，并通过在光束线上运行的 6 和 10 MV 光子束的测量数据进行了验证，其中包括带有和不带有平坦化滤波器的情况。在这项研究中，为了稳定光束，将平坦化滤波器替换为直线加速器供应商提供的 6 毫米厚的铜板。有几项研究表明，去除滤波器可以改善光子束的某些特性，这可能对放射治疗有益。对这种新光束进行了研究，包括输出、光谱、平均能量、半价层和散射光子的起源。结果表明，6 和 10 MV 光束在中心轴上的初始电子剂量输出分别增加了 1.76 和 2.66。与常规光束相比，来自加速器头的散射光子数量减少了（31.7±0.03）%（1 个标准差）（对于 6 MV 光束）和（47.6±0.02）%（对于 10 MV 光束）。与常规光束相比，未平坦化光束的光子能谱更软，并且即使对于最大射野尺寸（离轴 0-20 厘米），也不会随离轴距离显著变化。
