Comparison of Methods for RCR Component Selection From Computational Model Impedance Spectra

Vascular impedance represents the opposition to periodic blood flow though a network of vessels and is a good choice for use as a boundary condition for hemodynamic modeling. Vascular impedance can be computed using electrical analogs, such as two or three element Windkessel models, or computed from geometry using Womersley’s input impedance equations [3]. The challenges associated with using electrical analogs are the need for experimental data to determine appropriate component values and in determining an appropriate methodology to fit the experimental data to the simplified model. The challenges associated with using a geometry-based method are the necessity of knowing the geometry being modeled and the requirement of a periodic solution. While Windkessel models are routinely used in analyses, little detail is provided as to how these R and C parameters are extracted from the impedance spectra. Therefore, we examine the relative importance of matching different characteristics of impedance spectra to the resulting pressure and flow relationships.