Monte Carlo (MC) codes serve as the gold standard simulation tool during design and optimisation of x-ray imaging systems. Such simulations often model Rayleigh scattering based on the Independent Atom Approximation Model (IAM). This model neglects the low range molecular interference (MI) effects of non-crystalline materials such as human tissues. Previous work has found discrepancies in the simulated images of planar x-ray images between IAM and MI models. However, insignificant differences were found for computed tomography (CT) reconstructions. In this work we present Geant4 MC simulations of a flat panel source digital tomosynthesis (DT) system for human extremities. Results show that with a 1:9 scatter to primary ratio (SPR) in the x-ray projections, the DT reconstructions are insensitive to the differences of the IAM and MI models. Therefore, MC codes that use the IAM model are sufficient for the study of DT systems. That is because DT algorithms have a larger effect on image quality than the few percent change in the noise due to a physical model and noise suppression methods make this change even less important. Dependency of this conclusion on SPR must be considered in other DT modalities where SPR might be larger.

蒙特卡洛 (MC) 代码在 X 射线成像系统的设计和优化过程中充当黄金标准模拟工具。此类模拟通常基于独立原子近似模型 (IAM) 对瑞利散射进行建模。该模型忽略了非晶体材料（例如人体组织）的低范围分子干扰 (MI) 效应。以前的工作发现 IAM 和 MI 模型之间的平面 X 射线图像的模拟图像存在差异。然而，在计算机断层扫描 (CT) 重建中发现了微不足道的差异。在这项工作中，我们展示了用于人体四肢的平板源数字断层合成 (DT) 系统的 Geant4 MC 模拟。结果表明，在 X 射线投影中具有 1:9 的散射与初级比率 (SPR)，DT 重建对 IAM 和 MI 模型的差异不敏感。因此，使用 IAM 模型的 MC 代码足以研究 DT 系统。这是因为 DT 算法对图像质量的影响大于由于物理模型引起的噪声的百分之几变化，而噪声抑制方法使这种变化变得不那么重要。在 SPR 可能更大的其他 DT 模式中，必须考虑该结论对 SPR 的依赖性。