Simulating the hemodynamic effect in imaging brain tissue using two-photon laser scanning microscopy

Data interpretation of two-photon fluorescence microscopy on dyes with small signal change such as $\beta $\textit{-nicotinamide adenine dinucleotide }(NADH) faces enormous challenge because the measured signal change is often highly distorted by hemodynamic changes. Prior work modeled two-photon NADH fluorescence with precise maps of cortical microvasculature and corrected for the measured NADH signal change by using the fluorescence change of Sulforhodamine 101 (SR101), a functionally inert dye. The correction scheme, however, was not performed for a realistic three dimensional (3D) microvasculature. Here, we extend the prior work to calculate the point to point correction factor using a 3D microvasculature. We use ray tracing scheme and consider the effects of light scattering and absorption due to blood vessels. We will present the correction factors from multiple animal models and dyes; show its effect on data interpretation; and compare this correction scheme with the simple one-value approach. Our study allows more accurate interpretation of functional imaging studies.