Measurement of 2-D SpO2 distribution in skin tissue by multispectral imaging with depth selectivity control.

Two-dimensional hemoglobin oxygen saturation measurement is demonstrated by using the combination technique of multispectral imaging and the polarization control. Multispectral images are acquired at the wavelength range from 500 to 680 nm to observe the wavelength-dependent diffusely reflected light from the skin tissue. For eliminating the superficially reflected light from the skin, the skin tissue is illuminated by linearly polarized light and the polarization analyzer whose orientation is perpendicular to the illumination light is inserted in front of an imaging camera. The hemoglobin oxygen saturation levels corresponding to all image pixels are estimated by the partial least squares regression method with respect to each reflection spectrum. Mapping all the estimated values enables the oxygen saturation map across the observed tissue area.