In Vivo Three-Dimensional Velocity Vector Imaging and Volumetric Flow Rate Measurements

The three-dimensional (3-D) Transverse Oscillation (TO) method is used to obtain 3-D velocity vector estimates in two orthogonal planes. The method is suitable for a real-time implementation. Data are acquired using a Vermon 3.0 MHz 32x32 element 2-D phased array and the experimental ultrasound scanner SARUS. Measurements are conducted on a carotid artery flow phantom from Danish Phantom Design, and 20 frames are acquired with a constant flow rate of 16.7 +/- 0.17 mL/s provided by a Shelley Medical Imaging Technologies CompuFlow 1000 system. The peak velocity magnitude in the vessel is found to be 52.3 +/- 8.1 m/s compared to an expected peak velocity of 53.6 +/- 0.54 cm/s. Based on the out-of-plane velocity component in the cross-sectional plane, the estimated volumetric flow rates are 17.1 +/- 1.4 mL/s. The coefficient of variation is 8.3%, and the bias is 2.2%. An in vivo measurement of 3-D M-mode velocities is conducted over five heart beats. The peak systolic and end-diastolic velocities are 69 +/- 5.4 cm/s and 7.9 +/- 5.5 cm/s at the center of the vessel. For comparison, a commercial BK Medical ultrasound scanner using the spectral estimator yields 71.2 cm/s and 7.70 cm/s, respectively. The results demonstrate that the 3-D TO method can estimate 3-D velocities in two crossed planes, volumetric flow rates, and 3-D velocities in vivo.