Abstract
We propose a new optical coherence tomography (OCT) based method to measure red blood cell (RBC) velocities of single capillaries in the cortex of rodent brain. This OCT capillary velocimetry exploits quantitative laser speckle contrast analysis to estimate speckle decorrelation rate from the measured temporal OCT speckle signals, which is related to microcirculatory flow velocity. We hypothesize that OCT signal due to sub-surface capillary flow can be treated as the speckle signal in the single scattering regime and thus its time scale of speckle fluctuations can be subjected to single scattering laser speckle contrast analysis to derive characteristic decorrelation time. To validate this hypothesis, OCT measurements are conducted on a single capillary flow phantom operating at preset velocities, in which M-mode B-frames are acquired using a high-speed OCT system. Analysis is then performed on the time-varying OCT signals extracted at the capillary flow, exhibiting a typical inverse relationship between the estimated decorrelation time and absolute RBC velocity, which is then used to deduce the capillary velocities. We apply the method to in vivo measurements of mouse brain, demonstrating that the proposed approach provides additional useful information in the quantitative assessment of capillary hemodynamics, complementary to that of OCT angiography.
Highlights
Capillary is the smallest blood vessel in the body
The distal middle cerebral artery occlusion (dMCAO) usually results in a stop of blood flow in the barrel region of the somatosensory cortex, which is represented as deficit in number of capillaries perfused with red blood cell (RBC) in the angiogram (Fig. 5(b)) compared to pre-dMCAO (Fig. 5(a))
We introduced a new method of optical coherence tomography (OCT) velocimetry to measure velocity of RBC flow in perfused capillaries within mouse brain cortex
Summary
Capillary is the smallest blood vessel in the body. For mammals, its size is around 5 to 10μm in diameter, approximately the same order in the dimension of a red blood cell (RBC), constraining capillary blood flow to single RBC passage [1]. Tomita et al have reported a neuro-capillary coupling between neurons and capillary RBC motion, in which the neuronal activation modulated regional capillary blood flow in rat brain [3]. These findings have evidenced the involvement of cerebral capillary flow dynamics with the brain pathophysiology. To probe the capillary flow dynamics, usually, laser scanning fluorescence microscopy has been employed to image the motion of RBCs in individual capillaries [4,5]. It has been reported that RBC velocities in the single capillaries of a normal rat cerebral cortex are not uniform but highly heterogeneous, ranging from 0.1mm/s to 9.4mm/s with an average velocity of 1.96 ± 1.26mm/s (mean ± s.d) [5]. A main limitation of these methods is to monitor only one or a few capillaries at a time within the scan lines or the limited field of view, which provides a huge challenge in the investigation of capillary flow dynamics that requires flow measurement at multiple capillaries at the same time
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
