Investigation on vector Doppler method for carotid artery wall with focused transmit beams produced from a cross-shaped probe

Conventional methods for estimating 1D or 2D velocities were developed for the dynamic measurement of carotid walls. However, a carotid wall moves in 3D due to a heart pulsation, and the wall motion velocity in the longitudinal-axis cross-section is affected by out-of-plane displacements that cannot be measured with a 1D array probe. To estimate the out-of-plane displacement, we proposed the cross-shaped probe. The cross-shaped probe can estimate 3D velocity vector with 256 transmit-receive channels. Single or multiple focused beams were transmitted by the main array of the cross-shaped probe, and the RF signals received all the elements were used for 3D velocity vector estimation based on the multi-angle Doppler method. Numerical simulations and basic experiments showed that out-of-plane displacements in the longitudinal-axis cross section can be estimated. Furthermore, the in vivo experiments on a human common carotid artery showed that arterial wall motion during a cardiac cycle can be measured.