This research focuses on development of structured light imaging (SLI), a new optical imaging technique based on spatial frequency domain modulation. The goal of this method is to quantitatively measure and map tissue optical properties, absorption and scattering, to determine tissue biochemical structure and composition. The work presented here extends the technology's spatial and spectral frequency impact. First, to expand the depth sectioning capability of spatial frequency modulation, a layered tissue model was developed, validated and shown to accurately recover in vivo parameters in skin (epidermis and dermis), effectively filtering out signal from the underlying subcutaneous tissue. Next, to expand the impact of spectral frequency information, the SLI system was combined with a Computed Tomography Imaging Spectrometer (CTIS), which eliminates the need to scan through wavelengths when gathering multispectral information. A single SLI-CTIS measurement gathers 36 absorption maps and 36 scattering maps, with a resulting measurement speed ∼30 times faster than the liquid crystal tunable filter method currently employed in multispectral SLI systems. The multispectral information can be used to determine the concentrations of multiple tissue chromophores and the relative density of the tissue. This is immediately useful for monitoring the brain for signs of trauma, including monitoring of oxygen delivery across the brain, mapping of hemoglobin concentration to detect hemorrhage, mapping of water content to monitor edema, and mapping of tissue density to monitor swelling. A simple in vivo brain injury example is presented to demonstrate recovery of these parameters. Finally, to demonstrate the spatial, spectral and temporal resolution of the SLI-CTIS system, measurements were performed on in vivo mouse brain during seizure with electroencephalography (EEG) confirmation.
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