A novel ultrasound-based velocimetry technique (Echo PIV) for quantitative assessment of cardiovascular hemodynamics: Recent improvement, in vitro and in vivo validation, and its initial application in vascular profiling of human carotid arteries

Cardiovascular diseases are the world's largest killers, claiming 17.1 million lives a year. In cardiovascular diseases, atherosclerosis remains the leading cause of morbidity and mortality in the Western world. Recent studies showed that the blood flow hemodynamics and wall shear stress (WSS) play a localizing role in the cause of plaque formation. However, noninvasive and accurate assessment of blood flow information in human has always been a challenging problem, and the current clinical techniques, such as phase-contrast MRI (PC-MRI) and ultrasound Doppler all have some inherent limitations.;Echo particle image velocimetry (Echo PIV) is a novel ultrasound-based and easy-to-use method developed in our group. It can provide instantaneous whole-field mappings of multi-component velocity field with both high temporal and high spatial resolution. Meanwhile, it provides morphological information of blood vessels in one single measurement, from which, together with velocity fields, comprehensive hemodynamic information could be derived.;The Echo PIV technique/system has been improved by applying customized signal/image processing techniques as well as advanced PIV algorithms. The improved Echo PIV system has a temporal resolution up to 0.7 ms and a spatial vector resolution up to 0.4 mm in axial direction of the transducer. This technique was validated in a patient-specific carotid artery model under pulsatile flow condition with optical PIV providing reference measurements. Significant agreements were found between all measurements by echo and optical PIV.;The Echo PIV technique was as well validated in-vivo in assessing hemodynamics information in human right carotid artery against PC-MRI. The comparison analysis found good agreement between the measurements by the two modalities, with mean correlation coefficient of 0.92+/-0.05 for peak velocity, 0.94+/-0.05 for flow rate and 0.91+/-0.05 for WSS, respectively. The WSS in right common carotid artery (rCCA) positively correlates with peak velocity in rCCA (r=0.87, p<0.0001; n=28) and negatively with age of subjects (r=-0.60, p<0.001; n=28) and internal diameter of rCCA (r=-0.49, p=0.008; n=28). No correlation was found between WSS and flow rate.