Patient-specific modeling of cerebral blood flow: geometrical variations in a 1D model

Cerebral aneurysm growth is influenced by hemodynamical factors, which are commonly estimated by means of a computational fluid dynamics (CFD) model of a small 3D patient-specific segment of the arterial tree. Since direct in vivo assessment of the boundary conditions for the 3D segment is often not possible, the flow pulses are generally computed with a patient-generic 1D model. The aim of this study is to evaluate the necessity of, and requirements for, full patient-specific modeling, i.e., both geometry and boundary conditions based on patient data. The flow waveforms obtained with several models from literature and a patient-specific geometry of the arterial tree are compared and analysed. By comparing patient-specific and patient-generic models, it is investigated whether different but all reasonable modeling assumptions result in substantial differences in flow distribution. The flow pulses obtained at the boundaries of the arterial segment of interest are significantly affected by the 1D geometry and boundary conditions associated with the different modeling assumptions. The geometry as well as the in- and outflow conditions of the 1D model should be patient-specific, as they significantly influence the flow pulses to be prescribed at the boundaries of the 3D arterial segment.