Images of representative mouse skull samples are shown in Fig. 1, before (a) and after immersion for 30 min in (b). Before immersion in , blood is present in the bone tissues whereas after applying the sample is clearer, almost bloodless. For the first group of mice, the average absorption coefficients before and after immersion in are shown in Fig. 2. Coefficients varied from at 455 nm to at 705 nm before using . After treatment, the absorption coefficients varied from at 455 nm to at 705 nm. Data collected between 455 and 595 nm present a significant difference between both conditions (, ). Data collected between 595 and 705 nm do not present any statistically significant differences (, ). This is likely due to a lower contribution of blood to absorption at higher wavelengths. The standard error of the mean shows moderate interindividual variability, which is independent of wavelength and is comparable to what was observed previously.12 As expected, the absorption coefficient for fresh skull presents blood absorption peaks characteristics of oxy-haemoglobin absorption in the visible range with two maxima, respectively, at 537 and 568 nm. These two peaks strongly diminished after using . The average reduced scattering coefficients for the first group are shown in Fig. 3. Reduced scattering coefficients vary from at 455 nm to at 705 nm before and varied from at 405 nm to at 705 nm after . Coefficients are significantly different before versus after treatment for all the wavelengths (, ). The refractive index of hydroxyapatite (the main materials of the bone scatterers) is about 1.5, whereas refractive index of interstitial fluid is 1.35 to 1.36.13 Thus, the replacement of the interstitial fluid and bone by should induce refractive index matching and, so, decrease of reduced scattering coefficient. A hypothesis that requires further investigation would be that treatment leads to structural denaturation of bone, for example, by increasing bone porosity leading to the increase of the reduced scattering coefficient. A power law fit of the reduced scattering dependence with wavelength is classically observed for biological tissues.12,14 Here, it leads to before and after treatment ( in and in nm).