Abstract
Optical coherence Doppler tomography (ODT) is a promising neurotechnique that permits 3D imaging of the cerebral blood flow (CBF) network; however, quantitative CBF velocity (CBFv) imaging remains challenging. Here we present a simple phase summation method to enhance slow capillary flow detection sensitivity without sacrificing dynamic range for fast flow and vessel tracking to improve angle correction for absolute CBFv quantification. Flow phantom validation indicated that the CBFv quantification accuracy increased from 15% to 91% and the coefficient of variation (CV) decreased 9.3-fold; in vivo mouse brain validation showed that CV decreased 4.4-/10.8- fold for venular/arteriolar flows. ODT was able to identify cocaine-elicited microischemia and quantify CBFv disruption in branch vessels and capillaries that otherwise would have not been possible.
Highlights
Cerebral blood flow (CBF) plays a crucial role in brain physiology, metabolism and function
Neuroimaging techniques that enable high spatiotemporal resolution and quantitative imaging of the cerebral blood flow network and dynamics are of high clinical relevance and may provide important insight into brain physiology, brain function and to understand the mechanisms underlying neurovascular dysfunction of disease progression
The high spatiotemporal resolutions can be used to help delineate the different vessel compartments that contribute to fMRI blood-oxygenation level dependent (BOLD) signals, and assess whether the BOLD changes are due to flow rate (CBFv) and/or changes in vessel diameters
Summary
Cerebral blood flow (CBF) plays a crucial role in brain physiology, metabolism and function. To uncover the temporal-spatial patterns of neurovascular coupling during neural activity is of great importance for understanding functional variations in cerebral cortical. Intravital two-photon microscopy has been widely utilized to explore the velocity change of red blood cells (RBCs) in a microvascular vessel in response to brain stimulation by tracking the time-lapse shadowgraph of fluorescently labeled RBCs flowing through an individual micro-vessel [5]. The blood-oxygenation level dependent (BOLD) signal of fMRI provides hemodynamic information of the entire brain by sensing paramagnetic deoxyhaemoglobin in venous blood [6], but its limited spatial resolution does not allow for resolving vessel compartments and cannot distinguish flow changes from individual vessels, which can be important to understand the mechanisms of downstream responses to specific brain activations and brain dysfunction. There is a need to bridge the gap between these two groups of image modalities
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