Absorption, fluorescence, and dynamic scattering contrast in spatial frequency domain imaging (SFDI)

Quantitative characterization of tissue structure and function is a challenge due to structural heterogeneity and functional diversity across multiple spatial scales. Optical technologies are an inexpensive and safe method to visualize tissue at all spatial scales. Spatial Frequency Domain Imaging (SFDI) is a non-invasive, scan-free, and scalable field of view technology used to characterize tissue. Three SFDI instruments were developed to explore optical contrast mechanisms due to absorption, dynamic scattering, and fluorescence in tissue. For each platform, spectral and spatial frequency parameters were investigated in phantoms and in vivo to measure absorption for fast hemodynamics, fluorescence for accurate margin delineation, and dynamic light scattering for tissue perfusion. Based on these studies, a large field of view SFDI system was designed and constructed for intra-operative imaging. System validation was performed in pre-clinical models for free-flap measurement and sentinel lymph node mapping, and in a human subject during reconstructive surgery.