3D Doppler Angle Estimation Using Spectral Symmetry and Matrix Arrays

Doppler-based velocity estimation requires accurate knowledge of the beam-to-flow angle. Current threedimensional (3D) methods often rely on computationally demanding algorithms, such as volumetric speckle tracking or cross-correlation, which are difficult to execute in real-time. This paper presents a lightweight and robust procedure for Doppler angle estimation, which extends the two-dimensional method based on Spectral Symmetry Index (SSI) calculation to 3D using a matrix array probe. After vessel localization, a focused (reference) beam is dynamically steered across angle pairs , to sample a pyramidal angular volume. Multigate spectral Doppler (MSD) profiles are calculated for each angle pair, and SSI values are evaluated. A two-step coarse-to-fine scan refines the flow direction identification. Experimental validation was performed using a fully-parallel 1024-channel open ultrasound research platform and a commercial flow phantom scanned across 5 vessel orientations and 3 flow velocities. An angular estimation accuracy better than ± 1% was achieved, demonstrating robust performance.