A Unified Clutter and Noise Filter to Improve Ultrafast Power Doppler Image Quality

Ultrafast power Doppler (UPD) imaging can significantly improve the sensitivity of blood flow detection with plane wave imaging (PWI) and advanced spatiotemporal filters, compared with traditional power Doppler imaging. However, UPD image quality still suffers from clutter and noise due to the acoustic attenuation and reflection in the tissue, as well as the lack of transmit focusing in PWI. Methods proposed to suppress depth-dependent background noise and reject tissue clutters, including noise equalization, tophat filtering, and block-wise singular value decomposition (SVD), have failed to achieve the best tradeoff between vessel visualization and background suppression. We proposed a unified clutter and noise filter combining depth-dependent SVD and tophat filtering to improve the visualization of vessels and the UPD image quality. In vivo animal and human experiments were performed to acquire IQ data with linear and convex arrays, respectively. Results demonstrated that the proposed method shows a substantial improvement in image quality compared with conventional UPD implementation, with strong suppression of depth-dependent background noise, superior rejection of near-field tissue clutters, and clear depiction of vessel structures.