Spectral OA imaging exploits the wavelength-dependent optical absorption properties of specific chromophores in tissue (e.g. hemoglobin), with as goal to provide quantitative estimates of their spatially varying concentrations. A physiologically important example is the determination of local blood oxygen saturation, based on the distinct absorption spectra of oxy- and deoxyhemoglobin in the near-infrared range. This is of particular relevance for the study of oxygenation heterogeneity in tumors, the early detection and monitoring of cerebral ischemia in brain, and of other abnormalities characterized by a change in tissue oxygenation or perfusion status.
A central issue, which makes quantitative oxygenation measurements challenging, is the unknown extent of wavelength-dependent optical attenuation inside biological tissue. It engenders a spectral distortion of the recorded OA signals relative to the absorption spectrum of the chromophore's of interest. Only when this distortion is taken into account (which is referred to as "spectral correction"), a recovery of accurate quantitative information is possible.
As part of our research on quantitative deep OA imaging, we investigate techniques to correct for the spectral distortion of the recorded OA signals.
