Dynamic light scattering Monte Carlo: a method for simulating time-varying dynamics for ordered motion in heterogeneous media

Abstract

Few methods exist that can accurately handle dynamic light scattering in the regime between single and highly multiple scattering. We demonstrate dynamic light scattering Monte Carlo (DLS-MC), a numerical method by which the electric field autocorrelation function may be calculated for arbitrary geometries if the optical properties and particle motion are known or assumed. DLS-MC requires no assumptions regarding the number of scattering events, the final form of the autocorrelation function, or the degree of correlation between scattering events. Furthermore, the method is capable of rapidly determining the effect of particle motion changes on the autocorrelation function in heterogeneous samples. We experimentally validated the method and demonstrated that the simulations match both the expected form and the experimental results. We also demonstrate the perturbation capabilities of the method by calculating the autocorrelation function of flow in a representation of mouse microvasculature and determining the sensitivity to flow changes as a function of depth.

Fig. 1

Autocorrelation measurement setup for PDMS phantom experiments.

Fig. 2

Comparison of experimental and simulation results from PDMS phantom experiment. (a) Shows the simulation (−) and experimental (x) results at four different constant linear speeds. (b) and (c) show the simulated histograms of q · v and the number of scattering events.

Fig. 3

Example calculation of autocorrelation function of mouse cortical microvasculature. Two photon maximum intensity projection of microvasculature stack is shown in (a).

Fig. 4

The change in τ_c from a 95% change in flow velocity for the (a) surface vessel ROI and (b) parenchyma ROI in each 50 μm layer of the geometry.