Supplementary file 1_Estimating flow division in aortic branches of diseased aorta: a method for boundary condition specification in CFD analysis.docx

Hemodynamic predictions using computational fluid dynamics (CFD) simulations can provide valuable guidance assessing aortic disease risks. However, their reliability is hindered by the lack of patient-specific boundary conditions, particularly measured flow rates. This study addresses this knowledge gap by introducing a method for estimating flow division in aortic branches. The geometry of the lesional aorta was first repaired to obtain a near-healthy reference geometry. An iterative CFD simulation was then employed to estimate the flow division in the branches of the diseased aorta. Specifically, empirical boundary conditions from healthy individuals were used to predict the outlet pressures of reference geometry, which were subsequently converted into resistance models. These resistance models were then assigned to the outlets of the diseased aorta to predict the inlet pressure. The discrepancy between the predicted and target inlet pressures was iteratively minimized by adjusting the inlet pressure of the reference model until convergence was achieved. The final flow division in the branches of the diseased aorta was then obtained. The performance of the proposed method was investigated in three patients with aortic dissection or aneurysm. The proposed method predicted lower flow rates in branches with severe stenosis, which was more consistent with physiological expectations. Furthermore, the predicted blood pressure differed significantly from that obtained using the traditional method and was closer to the target values. The proposed method provides a practical solution for specifying boundary conditions in hemodynamic studies when clinically measured flow rates are unavailable.

利用计算流体动力学（CFD）模拟开展血流动力学预测，可为主动脉疾病风险评估提供重要指导。但由于缺乏患者特异性边界条件（尤其是实测流量），此类模拟的可靠性受到限制。本研究针对这一研究空白，提出了一种估算主动脉分支流量分配的方法：首先修复病变主动脉的几何形态，得到近似健康的参考几何模型；随后采用迭代CFD模拟，估算病变主动脉分支的流量分配。具体而言，先利用健康人群的经验边界条件预测参考几何模型的出口压力，继而将其转换为阻力模型；将该阻力模型赋予病变主动脉的出口，以预测其入口压力。通过调整参考模型的入口压力，迭代最小化预测入口压力与目标入口压力之间的偏差，直至收敛，最终得到病变主动脉分支的流量分配结果。本研究在3例主动脉夹层或动脉瘤患者中验证了所提方法的性能，结果显示：该方法对重度狭窄分支的流量预测值更低，更符合生理预期；此外，预测血压与传统方法所得结果存在显著差异，且更接近目标值。本研究为临床缺乏实测流量的血流动力学研究提供了一种实用的边界条件设定方案。