Validation of ultrasound velocity measurements against particle image velocimetry

Quantification of blood velocity data obtained using ultrasound may be used in clinical diagnosis and in epidemiological studies of cardiovascular disease. Quantities of interest are maximum velocity, velocity profiles and wall shear stress. We describe the use of particle image velocimetry (PIV) to validate blood velocity data from ultrasound. This involves two flow systems identical in vessel geometry and flow waveforms. One is optically transparent and used in a particle image velocimetry flow rig. The other is suitable for ultrasound imaging where the flow phantom is acoustically matched to human tissues. Straight tubes with varying degrees of focal lumen reduction were constructed to simulate carotid stenosis. The results show good agreement in the overall shape of the profiles throughout the phantoms. In both, flow was fully developed before the stenosis. Plug flow was observed through the stenosis. Downstream of the stenosis, an asymmetric jet formed with large zones of recirculation. For the two flow rates used, peak velocity for developed flow agreed to within 7%, and through the stenosis to within 15%. Wall shear stress values in the throat region had a mean agreement of 13%. The maximum velocities and WSS values in the post-stenotic region agreed to within 6% and 13% respectively.