Abstract
We introduce, validate and demonstrate a new software correlator for high-speed measurement of blood flow in deep tissues based on diffuse correlation spectroscopy (DCS). The software correlator scheme employs standard PC-based data acquisition boards to measure temporal intensity autocorrelation functions continuously at 50 - 100 Hz, the fastest blood flow measurements reported with DCS to date. The data streams, obtained in vivo for typical source-detector separations of 2.5 cm, easily resolve pulsatile heart-beat fluctuations in blood flow which were previously considered to be noise. We employ the device to separate tissue blood flow from tissue absorption/scattering dynamics and thereby show that the origin of the pulsatile DCS signal is primarily flow, and we monitor cerebral autoregulation dynamics in healthy volunteers more accurately than with traditional instrumentation as a result of increased data acquisition rates. Finally, we characterize measurement signal-to-noise ratio and identify count rate and averaging parameters needed for optimal performance.
Highlights
Blood flow is a clinical biomarker for tissue health because of its importance for oxygen delivery and clearance of metabolic byproducts, and Diffuse Correlation Spectroscopy (DCS) [1, 2] is emerging as the non-invasive optical method of choice to measure blood flow in tissues located 1 − 3 cms below the surface [3,4,5,6,7]
Besides the obvious cost advantages, fast sampling can reduce the imaging frame rate to seconds or less, enabling dynamic imaging. In this contribution we report on the development of a novel software correlator optimized for continuous, high-speed monitoring of deep tissue blood flow based on diffuse correlation spectroscopy (DCS)
We explore the utility of the real-time software correlator in the context of a critical clinical application wherein rapid acquisition of blood flow information is needed: measurement of cerebral autoregulation dynamics [41]
Summary
Blood flow is a clinical biomarker for tissue health because of its importance for oxygen delivery and clearance of metabolic byproducts, and Diffuse Correlation Spectroscopy (DCS) [1, 2] is emerging as the non-invasive optical method of choice to measure blood flow in tissues located 1 − 3 cms below the surface [3,4,5,6,7]. Photons collected from many (32 − 48) detector positions can be routed to a few (4 − 8) photon detectors via an optical switch In these cases, besides the obvious cost advantages, fast sampling can reduce the imaging frame rate to seconds or less (rather than minutes), enabling dynamic imaging
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