Time-Lagged Functional Ultrasound for Multi-Parametric Cerebral Hemodynamic Imaging

Area of Science:

• Neuroimaging
• Biomedical Engineering
• Physiology

Background:

• Functional ultrasound (fUS) is a promising neuroimaging technique.
• Quantifying hemodynamic changes like cerebral blood flow (CBF) and volume (CBV) is crucial for understanding brain function.
• Existing methods may have limitations in precisely distinguishing between different hemodynamic parameters.

Purpose of the Study:

• To introduce and validate a novel ultrasound speckle decorrelation-based time-lagged functional ultrasound (tl-fUS) technique.
• To quantify relative changes in cerebral blood flow speed (rCBFspeed), cerebral blood volume (rCBV), and cerebral blood flow (rCBF) during functional stimulations.
• To assess the capability of tl-fUS in differentiating and quantifying these hemodynamic parameters.

Main Methods:

• Development of the time-lagged functional ultrasound (tl-fUS) technique based on ultrasound speckle decorrelation.
• Utilization of numerical simulations and phantom experiments for initial validation.
• In vivo experiments using mouse brains to test the technique's performance during functional stimulations.

Main Results:

• The tl-fUS technique successfully quantified relative changes in rCBFspeed, rCBV, and rCBF.
• Blood volume changes were observed to be more pronounced in arterioles than in venules.
• Peak blood flow changes were approximately 2.5 times the peak blood volume changes during brain activation, consistent with prior literature.

Conclusions:

• The developed tl-fUS method effectively distinguishes and quantifies relative changes in rCBFspeed, rCBV, and rCBF.
• This technique provides valuable data for specific physiological interpretations of fUS measurements.
• tl-fUS advances the field of neurovascular coupling research and functional brain imaging.