Diagnostic minor stenoses in carotid artery bifurcation models using the disturbed velocity field

This paper presents a study on the diagnoses of minor stenoses at the non-divider side in the internal carotid artery of the carotid bifurcation using information provided by local disturbances of the flow field. The three-dimensional time-dependent flow fields in stenosed and non-stenosed bifurcation models were analyzed by means of both computational and experimental methods. The computational study indicates that in a model with a 50% area reducing stenosis, the global flow field is significantly disturbed as compared to that in a non-stenosed model. The main characteristic of the stenosed flow field is found in a peak systolic jet-flow distal to the stenosis, resulting in a significant diastolic post-stenotic flow separation area. In a 25% stenosed model, the induced disturbances are much less pronounced since the stenosis is located in the low shear area, which is well known to exist in the internal of non-stenosed artery bifurcations. A detailed experimental study was performed, applying laser Doppler velocity measurements in Plexiglas bifurcation models, in order to analyze the flow field (and its disturbances induced by minor [25%] stenoses) in either spatial, temporal or frequency domains. Analysis of the experimental data revealed that significant differences between stenosed and non-stenosed flow characteristics can be found. However, they probably cannot be used in clinical practice because of their sensitivity to inter-individual differences in bifurcation geometry and shape of the flow pulse.