Hyperspectral Algorithm for Mapping Tissue Oxygen Saturation

A simple algorithm based on computational estimates of spectral feature amplitudes in hyperspectral images is described for mapping oxygen delivery in tissue. Features are determined from contiguous image bands spanning the prominent absorption wavelengths of hemoglobin. Pixel values along the z-axis at each image coordinate establish a spectral curve. A reference baseline is obtained by linear interpolation between isosbestic points on the curve which are insensitive to changes in oxygen saturation of the blood. An oxygen-sensitive vector is determined from areas between the recorded curve and baseline, which estimates relative amounts of oxyhemoglobin and deoxyhemoglobin that contribute to the blood spectrum. Corrections are applied to account for variation in total light between recordings, and for the volume of blood at each pixel location in the recording. Here we apply the method to map relative oxygen saturation in the optic nerve head and overlying retinal vessels at normal and elevated intraocular pressure.