Quantitative assessment of renal arterial occlusion in a porcine model using spatial frequency domain imaging

We present the results of a feasibility study with spatial frequency domain imaging (SFDI) to produce quantitative measurements of optical property and chromophore concentration maps of three porcine kidneys utilizing a renal occlusion model at the near-infrared wavelengths of 658, 730, and 850 nm. Using SFDI, we examined the dynamics of absolute oxygen saturation (StO2). The mean StO2 for the kidneys varied from approximately 60% before occlusion, to 20% during occlusion, to 55% after reperfusion. We also present, for the first time to the best of our knowledge, reduced scattering coefficient (μ(s)') maps of the kidney during occlusion. We observed a substantial decrease in the wavelength dependence of scattering (i.e., scattering power) in the three kidneys, with a mean decrease of 18%±2.6%, which is indicative of an increase in scatterer size, and is likely due to tissue changes such as edema that follow from occlusion and inflammation.