Abstract
A high‐speed, contrast‐free, quantitative ultrasound velocimetry (vUS) for blood flow velocity imaging throughout the rodent brain is developed based on the normalized first‐order temporal autocorrelation function of the ultrasound field signal. vUS is able to quantify blood flow velocity in both transverse and axial directions, and is validated with numerical simulation, phantom experiments, and in vivo measurements. The functional imaging ability of vUS is demonstrated by monitoring the blood flow velocity changes during whisker stimulation in awake mice. Compared to existing Power‐Doppler‐ and Color‐Doppler‐based functional ultrasound imaging techniques, vUS shows quantitative accuracy in estimating both axial and transverse flow speeds and resistance to acoustic attenuation and high‐frequency noise.
Highlights
Functional quantitative in vivo imaging of the entire brain with high spatial and temporal resolution remains an open quest in biomedical imaging
Since the introduction of ultrafast plane wave emission-based Power Doppler functional ultrasound imaging (PD-fUS)[4], an increasing number of studies are exploiting the capabilities of PD-fUS for functional brain imaging studies[5,6,7]
We further developed a comprehensive experimental implementation and data processing methodology to apply vUS for blood flow velocity imaging of the rodent brain with high spatiotemporal resolution and without the need for exogenous contrast
Summary
Functional quantitative in vivo imaging of the entire brain with high spatial and temporal resolution remains an open quest in biomedical imaging. The microbubble tracking-based ultrasound localization microscopy (ULM[13]) method is able to map the whole mouse brain vasculature (coronal plane) and quantify the in-plane blood flow velocity (vULM[13,14]) with ~10 μm resolution. It suffers from a fundamental limitation of low temporal resolution as it requires extended data acquisition periods (~150 seconds for 75,000 images[13]) to accumulate. We further developed a comprehensive experimental implementation and data processing methodology to apply vUS for blood flow velocity imaging of the rodent brain with high spatiotemporal resolution and without the need for exogenous contrast. We further show its advantage over PD-fUS and CD-fUS in terms of quantitative accuracy in estimating axial and transverse flow speeds and its resistance to acoustic attenuation and high frequency noise through phantom and in vivo measurements
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