Measurement method of optical properties of ex vivo biological tissues of rats in the near-infrared range.

An optical fiber-based supercontinuum setup and a custom-made spectrophotometer that can measure spectra from 1100 to 2300 nm, are used to describe attenuation properties from different ex vivo rat tissues. Our method is able to differentiate between scattering and absorption coefficients in biological tissues. Theoretical assumptions combined with experimental measurements demonstrate that, in this infrared range, tissue attenuation and absorption can be accurately measured, and scattering can be described as the difference between both magnitudes. Attenuation, absorption, and scattering spectral coefficients of heart, brain, spleen, retina, and kidney are given by applying these theoretical and experimental methods. Light through these tissues is affected by high scattering, resulting in multiple absorption events, and longer wavelengths should be used to obtain lower attenuation values. It can be observed that the absorption coefficient has a similar behavior in the samples under study, with two main zones of absorption due to the water absorption bands at 1450 and 1950 nm, and with different absolute absorption values depending on the constituents of each tissue. The scattering coefficient can be determined, showing slight differences between retina and brain samples, and among heart, spleen and kidney tissues.