| Near-infrared light has been widely used in tissue optics due to low absorption. However, multiple scattering dominates light propagation at large distances, making it a challenge to use an optical method to image deep-tissue activities (> 1mm) directly. In the limit of multiple scattering, a diffusion approximation can be used to describe photon propagation inside the bulk tissue. When a long-coherence-length laser is used as an illumination source, speckles form on the tissue surface. The intensity of a single speckle fluctuates due to the motion of red blood cells inside the tissue. The fluctuation, quantified by an intensity temporal autocorrelation function (a measure of temporal coherence), is directly related to the average speed of red blood cells.;In this thesis, I first introduce the theory on how to reconstruct 3D blood flow distribution in deep tissue (> 1 mm) by measuring the temporal coherence of light on the tissue surface: namely, a technique called diffuse correlation tomography (DCT). Then, I describe how I constructed a DCT system and validated its performance through computer simulations and tissue phantom experiments. Finally, I present the results from the application of DCT to monitor blood flow changes in a healing mouse femoral graft, demonstrating the potential to non-invasively monitor deep tissue with a combination of optics and numerical computation. |
