Perpendicular ultrasound velocity measurement by 2D cross correlation of RF data. Part B: volume flow estimation in curved vessels

A novel axial velocity profile integration method, obtained from ultrasonic perpendicular velocimetry, for flow estimation in curved tubes was validated. In an experimental set-up, physiologically relevant curved geometries and flows were considered. Axial velocity profile measurements were taken by applying particle imaging velocimetry-based methods to ultrasound data acquired by means of a linear array transducer positioned perpendicular to the axial velocity component. Comparison of the assessed asymmetric velocity profiles to computational fluid dynamics calculations showed excellent agreement. Subsequently, the recently introduced cos theta-integration method for flow estimation was compared to the presently applied Poiseuille and Womersley models. The average deviation between the cos theta-integration-based unsteady flow estimate and the reference flow was about 5%, compared to an average deviation of 20% for both the Poiseuille and Womersley approximation. Additionally, the effect of off-centre measurement was analysed for the three models. It was found that only for the cos theta-integration method, an accurate flow estimation is feasible, even when it is measured off centre.