Improved Ultrasound Localization Microscopy Using United Spatial and Angular Adaptive Scaling Wiener Postfilter Based Beamformer

Ultrasound localization microscopy (ULM) was an emerging technique to visualize the morphology and hemodynamics of microvessels, which are usually invisible using conventional ultrasound imaging. Plane wave transmission with ultra-high frame rate is an important technology basis for ULM. However, the lack of transmission focus of plane wave causes low image quality, which degrades the subsequent microvascular imaging and decreases the accuracy of ULM. A united spatial and angular adaptive scaling wiener postfilter based beamformer (uSA-ASW) has been proposed to improve ultrafast power Doppler imaging (uPDI), which unites the spatial and angular dimensions of clutter-filtered blood flow data to estimate the signal power and noise power. Among these, the spatial coherence and angular coherence of signals are simultaneously utilized to suppress background noise as much as possible. In this paper, we applied uSA-ASW to ULM. The ULM velocity map obtained by delay-and-sum (DAS), coherence factor (CF), adaptive scaling Wiener postfilter (ASW), and uSA-ASW are compared. Results demonstrate that the proposed uSA-ASW beamforming method can effectively suppress background noise and improve the imaging quality of ULM.