Concerns have been raised about possible cancer risks after exposure to computed tomography (CT) scans in childhood. The health effects of ionizing radiation are then estimated from the absorbed dose to the organs of interest which is calculated, for each CT scan, from dosimetric numerical models, like the one proposed in the NCICT software. Given that a dosimetric model depends on input parameters which are most often uncertain, the calculation of absorbed doses is inherently uncertain. A current methodological challenge in radiation epidemiology is thus to be able to account for dose uncertainty in risk estimation. A preliminary important step can be to identify the most influential input parameters implied in dose estimation, before modelling and accounting for their related uncertainty in radiation-induced health risks estimates. In this work, a variance-based global sensitivity analysis was performed to rank by influence the uncertain input parameters of the NCICT software implied in brain and red bone marrow doses estimation, for four classes of CT examinations. Two recent sensitivity indices, especially adapted to the case of dependent input parameters, were estimated, namely: the Shapley effects and the Proportional Marginal Effects (PME). This provides a first comparison of the respective behavior and usefulness of these two indices on a real medical application case. The conclusion is that Shapley effects and PME are intrinsically different, but complementary. Interestingly, we also observed that the proportional redistribution property of the PME allowed for a clearer importance hierarchy between the input parameters.

翻译：关于儿童期接受计算机断层扫描（CT）后可能存在的癌症风险已引发广泛关注。电离辐射的健康效应通常根据受照器官的吸收剂量进行估算，而该剂量通过数值剂量学模型（如NCICT软件所提出的模型）计算得出。由于剂量学模型的输入参数通常存在不确定性，吸收剂量的计算本身也固有不确定性。当前辐射流行病学面临的方法论挑战之一，是在风险评估中充分考虑剂量不确定性。一个重要的初步步骤是，在建模并量化辐射相关健康风险估计中的不确定性之前，首先识别剂量估计中最具影响力的输入参数。本研究基于方差方法对全局敏感性进行分析，针对四类CT检查，对影响脑部与红骨髓剂量估计的NCICT软件中不确定输入参数进行影响程度排序。我们评估了两种适用于输入参数存在依赖关系的敏感性指标：Shapley效应与比例边际效应（PME）。通过实际医疗应用案例，首次比较了这两种指标的行为特性与实用性。研究结论表明，Shapley效应与PME本质不同但具有互补性。值得注意的是，我们观察到PME的比例再分配特性能够更清晰地体现输入参数间的重要性层级。