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首页> 外文期刊>Physics in medicine and biology. >Analytical calculation of the portal scatter to primary dose ratio: an EGS4 Monte Carlo and experimental validation at large air gaps.
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Analytical calculation of the portal scatter to primary dose ratio: an EGS4 Monte Carlo and experimental validation at large air gaps.

机译：门户散射与主要剂量比的分析计算：EGS4蒙特卡洛法和在大气隙下的实验验证。

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摘要

An analytical approximation for the scatter to primary dose ratio (SPR) on the central axis was validated against Monte Carlo results and experimental measurements for homogeneous and inhomogeneous phantoms. The analytical approximation only included first-order Compton scatter. The contribution to the total SPR from first-order Compton scatter, multiply scattered photons and electron scatter was investigated using Monte Carlo simulation for homogeneous phantoms (up to 30 cm thick for 6 and 18 MV beams; source to detector distances from 150 to 230 cm) as well as for a neck, thorax and pelvis phantom. SPRs were measured on the central axis with an ionization chamber for water phantoms (up to 20 cm thick at 4 MV, 30 cm for 6 MV and 10 MV and 40 cm for 18 MV; source to detector distances of 185 and 200 cm) and for phantoms representing the neck, thorax and pelvis (for air gaps of 50 cm and larger). The mean difference between the experimental and analytical SPRs on the central axis for source to detector distances of 170 cm or greater was within: -0.003 (neck); -0.012 (thorax); -0.028 (pelvis, 10 MV) and 0.008 (pelvis, 18 MV) respectively.
机译：相对于蒙特卡罗结果和均质和不均质体模的实验测量结果，验证了中心轴上散射与主要剂量比（SPR）的解析近似值。解析近似值仅包括一阶康普顿散射。使用蒙特卡罗模拟法对均质体模（6和18 MV光束最大厚度为30厘米;从源到探测器的距离为150至230厘米）使用一阶康普顿散射，多重散射光子和电子散射对总SPR的贡献进行了研究）以及颈部，胸部和骨盆幻影。用电离室对水体模在中心轴上测量SPR（4 MV时最大厚度为20厘米，6 MV和10 MV时最大为30厘米，18 MV时为40厘米;源到检测器的距离为185和200厘米）和用于代表颈部，胸部和骨盆的体模（用于50厘米或更大的气隙）。源到探测器的距离为170 cm或更大，中心轴上的实验SPR和分析SPR的平均差在-0.003（颈）内; -0.012（胸部）; -0.028（骨盆，10 MV）和0.008（骨盆，18 MV）。

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