School of Applied Sciences and Health Innovations Research Institute, RMIT University, Melbourne, Australia.
Med Phys. 2012 Apr;39(4):1769-78. doi: 10.1118/1.3689810.
The most appropriate method of evaluating the effective atomic number necessitates consideration of energy-dependent behavior. Previously, this required quite laborious calculation, which is why many scientists revert to over-simplistic power-law methods. The purpose of this work is to develop user-friendly software for the robust, energy-dependent computation of effective atomic numbers relevant within the context of medical physics, superseding the commonly employed simplistic power law approaches.
Visual Basic was used to develop a GUI allowing the straightforward calculation of effective atomic numbers. Photon interaction cross section matrices are constructed for energies spanning 10 keV to 10 GeV and elements Z = 1-100. Coefficients for composite media are constructed via linear additivity of the fractional constituents and contrasted against the precalculated matrices at each energy, thereby associating an effective atomic number through interpolation of adjacent cross section data. Uncertainties are of the order of 1-2%.
Auto-Z(eff) allows rapid (∼0.6 s) calculation of effective atomic numbers for a range of predefined or user-specified media, allowing estimation of radiological properties and comparison of different media (for instance assessment of water equivalence). The accuracy of Auto-Z(eff) has been validated against numerous published theoretical and experimental predictions, demonstrating good agreement. The results also show that commonly employed power-law approaches are inaccurate, even in their intended regime of applicability (i.e., photoelectric regime). Furthermore, comparing the effective atomic numbers of composite materials using power-law approaches even in a relative fashion is shown to be inappropriate.
Auto-Z(eff) facilitates easy computation of effective atomic numbers as a function of energy, as well as average and spectral-weighted means. The results are significantly more accurate than normal power-law predictions. The software is freely available to interested readers, who are encouraged to contact the authors.
评估有效原子序数的最恰当方法需要考虑能量相关的行为。以前，这需要相当繁琐的计算，这就是为什么许多科学家回归到过于简单的幂律方法的原因。本工作的目的是开发用于稳健、能量相关的有效原子序数计算的用户友好型软件，以取代常用的简单幂律方法，这些方法适用于医学物理学背景。
使用 Visual Basic 开发了一个图形用户界面（GUI），允许简单地计算有效原子数。构建了跨越 10keV 至 10GeV 能量范围和元素 Z=1-100 的光子相互作用截面矩阵。复合材料的系数通过各分数成分的线性加和构建，并在每个能量与预先计算的矩阵进行对比，从而通过相邻截面数据的插值关联有效原子数。不确定性约为 1-2%。
Auto-Z(eff)允许快速（约 0.6s）计算一系列预定义或用户指定的介质的有效原子数，从而可以估计辐射性质并比较不同的介质（例如评估水等效性）。Auto-Z(eff)的准确性已经通过大量已发表的理论和实验预测进行了验证，结果表明吻合良好。结果还表明，即使在其预期的适用范围内（即光电区），常用的幂律方法也是不准确的。此外，即使以相对方式比较复合材料的有效原子数也被证明是不合适的。
Auto-Z(eff)方便地计算了作为能量函数的有效原子数以及平均和谱加权平均值。结果比正常的幂律预测准确得多。该软件可供感兴趣的读者免费使用，鼓励读者与作者联系。
