Multi-spectral mueller matrix imaging polarimetry for studies of human tissues

The potential of Mueller matrix imaging polarimetry to become a new efficient technique for the optical biopsy and proper cancer staging was explored by measuring the exvivo samples of human tissues. Multi-spectral polarimetric images of both human colon and uterine cervix specimens reveal the enhanced contrasts between healthy and cancerous zones, compared to the unpolarized intensity images. For the understanding of physical origins of the observed polarimetric contrasts the Mueller matrix images of human colon tissue were simulated by Monte Carlo technique using multilayer optical model of tissue. The modeling results were compared with experimental data and confirmed that detected light is mainly backscattered by the objects small compared to the wavelength of probing light. The phenomenological model (decomposition of Mueller matrix into the product of elementary Mueller matrices of the homogeneous diattenuator, retarder, and depolarizer) was used for the quantitative characterization of the measured specimens in terms of their "effective" depolarization power, scalar birefringence and orientation of optical axis. The resulting polarimetric maps of the specimens were compared with the analysis of histological slides of corresponding specimen by anatomopathologists which is considered to be "gold-standard" in diagnostics. The general trends for depolarization and scalar birefringence values at different wavelengths confirmed the capability of Mueller polarimetry to differentiate between healthy and diseased tissue zones.