Quantitative blood flow velocity imaging using laser speckle flowmetry

Laser speckle flowmetry suffers from a debated quantification of the inverse relation between decorrelation time (tau(c)) and blood flow velocity (V), i.e. 1/tau(c) = alpha V. Using a modified microcirculation imager (integrated sidestream dark field - laser speckle contrast imaging [SDF-LSCI]), we experimentally investigate on the influence of the optical properties of scatterers on alpha in vitro and in vivo. We found a good agreement to theoretical predictions within certain limits for scatterer size and multiple scattering. We present a practical model-based scaling factor to correct for multiple scattering in microcirculatory vessels. Our results show that SDF-LSCI offers a quantitative measure of flow velocity in addition to vessel morphology, enabling the quantification of the clinically relevant blood flow, velocity and tissue perfusion.