title: Establishing the diffuse correlation spectroscopy signal relationship with blood flow.
abstract: Diffuse correlation spectroscopy (DCS) measurements of blood flow rely on the sensitivity of the temporal autocorrelation function of diffusively scattered light to red blood cell (RBC) mean square displacement (MSD). For RBCs flowing with convective velocity [Formula: see text], the autocorrelation is expected to decay exponentially with [Formula: see text], where [Formula: see text] is the delay time. RBCs also experience shear-induced diffusion with a diffusion coefficient [Formula: see text] and an MSD of [Formula: see text]. Surprisingly, experimental data primarily reflect diffusive behavior. To provide quantitative estimates of the relative contributions of convective and diffusive movements, we performed Monte Carlo simulations of light scattering through tissue of varying vessel densities. We assumed laminar vessel flow profiles and accounted for shear-induced diffusion effects. In agreement with experimental data, we found that diffusive motion dominates the correlation decay for typical DCS measurement parameters. Furthermore, our model offers a quantitative relationship between the RBC diffusion coefficient and absolute tissue blood flow. We thus offer, for the first time, theoretical support for the empirically accepted ability of the DCS blood flow index ([Formula: see text]) to quantify tissue perfusion. We find [Formula: see text] to be linearly proportional to blood flow, but with a proportionality modulated by the hemoglobin concentration and the average blood vessel diameter.
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: David A
authors.initials: DA
authors.lastname: Boas
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: Sava
authors.initials: S
authors.lastname: Sakadžić
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: Juliette
authors.initials: J
authors.lastname: Selb
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: Parisa
authors.initials: P
authors.lastname: Farzam
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: Franceschini
authors.affiliation: MGH/HST Athinoula A. Martinos Center for Biomedical Imaging , Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, United States.
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Carp
keywords: Monte Carlo; blood flow; diffuse correlation spectroscopy; photon migration