Frame‑wise weighted resolution‑enhanced power Doppler ultrasound for microvascular structural and functional imaging

Advances in ultrasound acquisition and clutter suppression have established microvascular Power Doppler imaging (PDI) as a valuable tool for clinical diagnosis and neurovascular research. However, conventional PDI remains limited by insufficient spatial resolution and contrast, which restrict detailed vessel delineation and microvascular quantification. In this study, we develop a frame-wise weighted resolution-enhanced PDI (FW-WE PDI) framework that improves spatial resolution and contrast by applying an MSSR-derived spatial super-resolution process as a multiplicative weight to each clutter-suppressed blood-flow frame. This weighting approach is adapted to the physics of ultrasound speckle, enabling sharpening of the speckle main lobe and reduction of spatial diffusion of blood-flow energy while preserving the physiological meaning of Doppler power. Scatterer-based simulations and microbubble-trajectory phantom experiments elucidate the mechanisms through which the proposed method enhances microvascular PDI. Validation across contrast-enhanced and label-free datasets from rat brain, mouse liver, kidney, tumor, and human heart demonstrates two- to threefold improvements in spatial resolution together with substantial gains in vessel-to-background contrast. Furthermore, in neurofunctional ultrasound experiments, FW-WE PDI reveals subtle high-resolution brain activation patterns that are undetectable with conventional PDI. These results indicate that FW-WE PDI provides a practical, hardware-agnostic enhancement to microvascular and functional ultrasound imaging, enabling higher-fidelity morphological and hemodynamic assessment in both research and clinical settings.