Fig. 3: The SC method enables in vivo fast super-resolution vascular imaging.

Super-resolution ultrasound vascular imaging of a mouse hindlimb using a SC-ULM, b PSF-CC ULM, and c power-Doppler methods. All the images are recorded from 1.5 sec of data acquisition (DAQ). d The image saturation as a function of DAQ times in SC-ULM (blue) and PSF-CC ULM images (black), respectively. The averaged saturation is calculated from 96125 pixels from three randomly selected regions of interest (ROI) in the vascular structures. The error bars are standard deviations (N = 3). The solid curves are fitted through an asymptotic regression model with an asymptote at 1. The characteristic times are 1.5 and 32.5 sec with SC-ULM and PSF-CC ULM, respectively. The latter is calculated through extrapolation because PSF-CC is slow and cannot reach the same saturation in 12 sec. e The zoom-in view of vascular structures using SC-ULM (top row) and PSF-CC ULM (bottom row) at various DAQ times from 0.5 to 7 sec, respectively. The area shown here is marked by the white rectangles in a and b. The result shows SC-ULM reveals the structure of major vessels at 0.5 sec and nearly complete structures in 1.5 sec, while the PSF-CC image remains sparse after 7 sec. f, g resolution measurements using the Fourier ring correlation (FRC) method of SC-ULM and PSF-CC ULM at 1.5 sec of DAQ in (e), respectively. h The resolution of both methods as a function of DAQ times. The averaged resolution is calculated from four random ROIs with the FRC method. The center line in each box is the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers range of each box is within 1.5 interquartile. Scatter plots of the data used for the boxplot are overlaid on each boxplot. *p = 0.0015, ns denotes not significant.