Optical clearing of human dura mater

The changes in the optical parameters of the human dura mater in the spectral range 400–700 nm caused by the action of an aqueous solution of mannitol with a concentration of 0.16 g/ml are studied in vitro. The diffusion of mannitol into the tissue leads to a partial matching between the refractive indices of the structure-forming elements (the collagen fibrils) and the base substance of the dura mater (the interstitial fluid). As a result, the light scattering by the biological tissue in the entire spectral range under study is decreased, on the average, by a factor of 1.5–2. The immersion of the biological tissue is shown to cause a decrease in the absorption of the dura mater in the range of the blood absorption bands by a factor of 1.2–1.6. The results presented may prove to be useful in the laser therapy and optical diagnostics of brain diseases.