Fluence compensated optoacoustic measurements of blood oxygen saturation in vivo at two optimal wavelengths

Non-invasive measurement of blood oxygen saturation in blood vessels is a promising clinical application of optoacoustic imaging. However, unknown spatial and spectral distribution of optical fluence within biotissue challenges precise multispectral optoacoustic measurements of blood oxygen saturation. The accuracy of the blood oxygen saturation measurement can be improved by the choice of optimal laser wavelengths. We propose the numerical approach to determine the optimal wavelengths for two-wavelengths OA measurements of blood oxygen saturation at various depths. The developed approach accounts for acoustic pressure noise, error in determination of optical scattering and absorption coefficients used for the calculation of the optical fluence, and diameter of the investigated blood vessel. We demonstrate that in case of an unknown (or partially known) fluence spatial distribution at depths between 2 and 8 mm, minimal error in the determination of blood oxygen saturation is achieved at the wavelengths of 658±40 nm and 1069±40 nm. We report on the pilot results of OA in vivo measurements of blood oxygen saturation using optimal wavelengths obtained by the proposed approach.