P.043 Application of Womersley Theory: Estimation of Pulse Volume Flow and Wall Shear Stress in Large Artery Using Ultrasound

Abstract

In order to assess pulse volume flow (PVF) and wall shear stress (WSS) in large arteries by the means of ultrasound, a Womerlsey theory based iterative method is proposed. Firstly, the PVF is computed by integrating the estimated velocity profiles obtained from multi-gate ultrasound Doppler; the vessel diameter was assessed through M-mode ultrasound. Secondly, an algorithm was applied in order to determine the PVF that gives the optimal fit of the core velocities estimated by ultrasound to the ones obtained through Womersley theory applied for tubes with none moving walls. The WSS is consequently computed from the fitted Womerlsey profiles. The PVF and WSS obtained through this method were compared to the ones given by Poiseuille theory. The method was applied on measurements performed on the brachial artery, repeated at least three times, of 9 presumed healthy volunteers. The results displayed a large relative difference in average maximal PVF (27±7%, p < 0.01) and WSS (72±36%, p < 0.01), the intra individual variations being 4±9% for the PVF and 11±6% for the WSS. In the case of the mean PVF and WSS, relative differences of 6±8% (p < 0.05) and –1±15% (p <1) respectively were evidentiated. The estimations based on Poiseuille theory present a significant underestimation of both maximum and mean PVF as well as maximum WSS by comparison to the results obtained through Womersley profiles fitting. No significant difference was observed for the mean WSS.