Early detection of asymptomatic carotid stenosis may help identifying individuals at risk of stroke. We explore a new method based on laser Doppler vibrometry (LDV) which could allow the non-contact detection of stenosis from neck skin vibrations due to stenosis-induced flow disturbances. Experimental fluid dynamical tests were performed with water on a severely stenosed patient-specific carotid bifurcation model. Measurements were taken under various physiological flow regimes both in a compliant and stiff-walled version of the model, at 1 to 4 diameters downstream from the stenosis. An inter-arterial pressure catheter was positioned as reference. Increasing flow led to corresponding increase in power spectral density (PSD) of pressure and LDV recordings in the 0–500 Hz range. The stiff model lead to higher PSD. PSD of the LDV signal was less dependent on the downstream measurement location than pressure. The strength of the association between PSD and flow level, model material and measuring location was highest in the 0–50 Hz range, however useful information was found up to 200 Hz. This proof-of-concept suggests that LDV has the potential to detect stenosis-induced disturbed flow. Further computational and clinical validation studies are ongoing to assess the sensitivity and specificity of the technique for clinical screening.
(1) Background: We aimed to assess the validity of laser Doppler vibrometry (LDV) as an emerging method to measure the local pulse wave velocity (PWV) from skin displacement generated by the pressure pulse inside an underlying artery. (2) Methods: A finite element model representing a simplified common carotid artery embedded within a soft tissue mimicking material was used to reproduce how tissue motions due to a wave propagation along the artery radiates to the skin surface. A parametric study was set up, varying: (i) the pressure conditions inside the artery (shock and traveling pressure impulse), (ii) the arterial depth and (iii) the geometry in a patient-specific artery model. (3) Results: under all conditions, the arterial pulse induced primary and secondary waves at the skin surface; of which the propagation speed deviated from the imposed PWV (deviations between −5.0% to 47.0% for the primary wave front). (4) Conclusions: the propagation of a short pressure impulse induced complex skin displacement patterns revealing a complicated link between PWV and measured propagation speeds at the skin surface. Wave propagation at the skin level may convey information about arterial PWV, however, advanced signal analysis techniques will be necessary to extract local PWV values.
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