Omnidirectional ultrasound tomographic vector flow imaging with ring-array transducer

In conventional ultrasound (US) vector flow imaging (VFI) with linear array transducers, the limited aperture size restricts the detection of lateral Doppler frequency shifts, thereby limiting omnidirectional flow imaging capabilities and causing inaccuracies in vector flow reconstruction. In this study, we propose employing a ring-array US transducer that fully encloses the imaged object to interrogate frequency shifts from all directions. This approach, termed ultrasound tomographic vector flow imaging (UST-VFI), enables accurate estimation of both axial and lateral components of flow vectors based on the detected Doppler frequency shifts in each tomographic view, using a least-squares estimator. Proof-of-concept results from a rotary disk phantom demonstrated clear enhancements in uniformity and a reduction in angle-dependent errors in both the magnitude and phase of the estimated flow vectors. Once the method is fully developed, ultrasound tomography could enable the analysis of blood flow dynamics in response to pathological changes, such as breast tumor progression and treatment response.