The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part I. Laser and ultrasonic Doppler flow studies

Irregular carotid lesion surface is considered as a factor increasing the risk of the cerebral embolism. The objective of the study was to investigate the possibility to distinguish models of stenosed carotid bifurcation with lesion irregularity on the basis of the properties of flow velocity distributions. Two groups of elastic replicas of carotid bifurcations with different stenosis degree were investigated. Each group consisted of three models with different severity of plaque surface irregularity and one with smooth wall. Velocity data were collected using a one-component laser Doppler anemometer (LDA) system and a pulsed Doppler flowmeter. The LDA velocity distributions and Doppler spectral broadening index, turbulence intensity index and coefficient of skewness were analysed. sion irregularity resulted in change of the size and/or shape of reversed/reduced flow areas and of the position of the jet with respect to those observed in a smooth wall model. The flow features observed in the ultrasonic Doppler spectra were generally coherent with the axial LDA velocity distributions. Doppler spectral parameters demonstrated different sensitivities to the severity of the wall irregularity, however, the complexity of curves of these indices versus time did not allow to draw decisive conclusions and implied use of a more sensitive tool of analysis.