Nowadays, biophotonics is widely used in neuroscience. The effectiveness of biophotonic techniques, such as fluorescence imaging and optogenetics, is affected by the optical properties of the examined tissue. Therefore, knowledge of these properties is essential to carefully plan experiments. Mice and rats are widely used in neuroscience studies. However, reports about optical properties of their brains are very rare. We measured optical absorption <i>μ<sub>a</sub></i> and reduced scattering <i>μ’<sub>s</sub></i> coefficients of native rat brain in the visible and near-infrared wavelength region, using contact spatially resolved spectroscopy (SRS). In this study, we estimate <i>μ<sub>a</sub></i> and <i>μ’<sub>s</sub></i> for the rat cortex and discuss their stability in time. Additionally, variations in optical properties within and between samples were characterized. The results extend the range of known optical properties for the rat cortex, especially in the visible range, relevant to optogenetics. <i>μ<sub>a</sub></i> and <i>μ’<sub>s</sub></i> are stable within a time span of four hours, and show low variation in and between brain samples. This indicates that a suitable protocol was used to estimate optical properties of rodent brain tissue. Since contact SRS is a non-destructive method, this technique could be used also to measure <i>μ<sub>a</sub></i> and <i>μ’<sub>s</sub></i> in living animals. Moreover, the probe has small dimensions, allowing the characterization of optical properties in different structures of the brain.
A contact spatially resolved spectroscopy (SRS) setup based on a fiber-optics probe in the Vis/NIR range (400-1000 nm) was
developed, calibrated, and validated for its measurements and optical properties estimation by means of a metamodeling method
on a set of liquid optical phantoms. Thirty Braeburn apples cultivated in sub-fertilization condition were harvested and measured
before and after shelf-life storage (2 weeks at 18 °C) by the setup and were analyzed for quality attributes (firmness and soluble
solids contents (SSC)) by destructive reference methods. Estimated optical properties (absorption and reduced scattering
coefficients) acquired from SRS measurements at the beginning and the end of the shelf-life indicated changes in chemical
composition of the apples. Partial Least Squares Regression (PLSR) was employed to construct calibration models relating the
estimated optical properties to the reference quality attributes. The constructed PLS models based on the absorption coefficient
spectra gave good prediction performance for the quality attributes of the apples in the validation set with correlation coefficients
r of 0.901 and r of 0.844, respectively for SSC and firmness. The obtained results clearly show the potential of the SRS
measurements for nondestructive quality evaluation of apples.
Food quality is critically determined by its microstructure and composition. These properties could be quantified noninvasively
by means of optical properties (absorption and reduced scattering coefficients) of the food samples. In this
research, a spatially-resolved spectroscopy setup based on a fiber-optic probe was developed for acquiring spatiallyresolved
diffuse reflectance of three sugar foams with different designed microstructures in the range 500 - 1000 nm. A
model for light propagation in turbid media based on diffusion approximation for solving the radiative transport equation
was employed to derive optical properties (absorption and reduced scattering coefficients) of these foams. The accuracy
of this light propagation model was validated on four liquid phantoms with known optical properties. The obtained
results indicated that the optical properties estimation was successfully validated on these liquid phantoms. The
estimated reduced scattering coefficients μs' of the foams clearly showed the effect of foaming time on their
microstructures. The acquired absorption coefficients μa were also in good agreement with the designed ingredients of
these sugar foams. The research results clearly support the potential of spatially-resolved spectroscopy for nondestructive
food quality inspection and process monitoring in the food industry.