title: Fast blood flow monitoring in deep tissues with real-time software correlators.
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.
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA; Interdisciplinary Laboratory of Physics and Biomedicine, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China.
authors.forename: Detian
authors.initials: D
authors.lastname: Wang
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Ashwin B
authors.initials: AB
authors.lastname: Parthasarathy
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Wesley B
authors.initials: WB
authors.lastname: Baker
authors.affiliation: Div. of Stroke and Neurocritical Care, Hospital of the University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Gannon
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Venki
authors.initials: V
authors.lastname: Kavuri
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Ko
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Schenkel
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA; State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Li
authors.affiliation: Interdisciplinary Laboratory of Physics and Biomedicine, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China.
authors.forename: Zeren
authors.initials: Z
authors.lastname: Li
authors.affiliation: Div. of Stroke and Neurocritical Care, Hospital of the University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Mullen
authors.affiliation: Div. of Stroke and Neurocritical Care, Hospital of the University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Detre
authors.affiliation: Dept. of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 USA.
authors.forename: Arjun G
authors.initials: AG
authors.lastname: Yodh
keywords: (030.0030) Coherence and statistical optics; (030.5260) Photon counting; (030.5290) Photon statistics; (110.4153) Motion estimation and optical flow; (170.1470) Blood or tissue constituent monitoring; (170.1610) Clinical applications; (170.2655) Functional monitoring and imaging; (170.3880) Medical and biological imaging; (170.5270) Photon density waves; (170.6480) Spectroscopy, speckle; (170.6510) Spectroscopy, tissue diagnostics; (290.4210) Multiple scattering