Fast blood flow monitoring in deep tissues with real-time software correlators

Abstract

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. References and links 1. D. A. Boas, L. E. Campbell, and A. G. Yodh, "Scattering and imaging with diffusing temporal field correlations," Phy. Rev. Lett. 75, 1855Lett. 75, -1858Lett. 75, (1995

Assessment of a multi-layered diffuse correlation spectroscopy method for monitoring cerebral blood flow in adults

“…8, despite the presence of a relatively thick extracerebral layer (of the order of 1 cm). The ML DCS technique could be further optimized by incorporating optical property measurements for the different tissue layers and by improving the SNR through the use of a software correlator to measure only relevant correlations times [49]. Recent improvements for monitoring CBF were demonstrated in the adult head by a pressure modulation algorithm, without requiring a priori anatomical information [24].…”

Clinical applications of near-infrared diffuse correlation spectroscopy and tomography for tissue blood flow monitoring and imaging

“…This is due to the utilization of single-mode detector fibers with a small core diameter of 5 μm in DCS/DCT measurements to ensure the detection of autocorrelation functions of light intensity. Efforts have been made to improve SNR through the spatial average of multiple autocorrelation functions detected by a detector fiber bundle (Dietsche et al , 2007) or the temporal average of DCS signals obtained by a fast software correlator (Wang et al , 2016). …”

Highly parallel, interferometric diffusing wave spectroscopy for monitoring cerebral blood flow dynamics

“…Taking advantage of the parallel multispeckle detection of our iDWS system, we monitored high-speed pulsatile blood flow dynamics in the human brain in vivo [18,19,34,35]. A healthy adult human subject sat on a chair with her head placed on a chin rest.…”

“…(S8). Typical optical properties of ${{\mu }^{\prime }}_s=7.38$ cm −1 and μ a = 0.12 cm −1 [35] were assumed for brain tissue. The estimated BFI time course in Fig.…”