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Relevant chemotherapy-induced changes to intra-tumor heterogeneity occur at multiple length scales, but few imaging methods are capable of simultaneous multiscale monitoring. We have developed a multiscale imaging technique called Diffuse and Nonlinear Imaging (DNI) that uses Spatial Frequency Domain Imaging (SFDI) for wide-field mapping of tumor optical properties and hemodynamics, and Multiphoton Microscopy (MPM) to image tumor micro-vessel and collagen architecture, and endogenous metabolic molecules with cellular resolution. Importantly, DNI co-registers MPM throughout the SFDI field-of-view. The SFDI system uses LEDs to illuminate a digital micro-mirror device with near-infrared wavelengths (650-850 nm) to project structured intensity patterns onto a sample, with diffuse reflectance collected by a CCD camera. The extended wavelength (680-1300 nm) MPM system consists of a femtosecond tunable laser for two-photon excitation (TPE) of fluorescently labeled microvasculature, Second Harmonic Generation imaging of collagen, and TPE auto-fluorescence of intracellular NADH and FAD.
We have conducted in vivo DNI monitoring of a syngeneic murine mammary tumor model (Py230) through a mammary imaging window in 10 untreated C57BL/6 female mice. Our initial results revealed that global hemoglobin concentrations and micro-vessel density were highly correlated (ρ = 0.83). This presentation will report on multiscale relationships among tumor hemodynamic, microenvironment, and metabolic metrics, as well as on Monte Carlo modeling and phantom studies comparing depth penetration between the two imaging regimes. In the future, DNI will be used to evaluate chemo-resistance over a range of spatial scales and contrast mechanisms to obtain a more complete picture of the in vivo tumor state.
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