Multiexposure laser speckle contrast imaging of the angiogenic microenvironment.

We report the novel use of laser speckle contrast imaging (LSCI) at multiple exposure times (meLSCI) for enhanced in vivo imaging of the microvascular changes that accompany angiogenesis. LSCI is an optical imaging technique that can monitor blood vessels and the flow therein at a high spatial resolution without requiring the administration of an exogenous contrast agent. LSCI images are obtained under red (632 nm) laser illumination at seven exposure times (1-7 ms) and combined using a curve-fitting approach to obtain high-resolution meLSCI images of the rat brain vasculature. To evaluate enhancement in in vivo imaging performance, meLSCI images are statistically compared to individual LSCI images obtained at a single exposure time. We find that meLSCI reduced the observed variability in the LSCI-based blood-flow estimates by 30% and improved the contrast-to-noise ratio in regions with high microvessel density by 41%. The ability to better distinguish microvessels, makes meLSCI uniquely suited to longitudinal imaging of changes in the vascular microenvironment induced by pathological angiogenesis. We demonstrate this utility of meLSCI by sequentially monitoring, over days, the microvascular changes that accompany wound healing in a mouse ear model.