Systems are provided for detecting the flow of blood or other fluids in biological tissue by illuminating the biological tissue with a coherent light source and detecting time-varying patterns of constructive and destructive interference in light received from portions of the biological tissue by an imager. The movement of blood cells and other light-scattering elements in the biological tissue causes transient, short-duration changes in light emitted from portions of the biological tissue proximate to the moving blood cells or other scatterers. High-frequency sampling or other high-bandwidth processing of light intensities detected by an imager could be used to determine the flow of blood or other fluids at a plurality of points in the biological tissue, to detect and/or localize a tumor in the biological tissue, to determine the location, pattern, width, or other properties of vasculature in the biological tissue, or to provide information for some other application(s).
