Abstract
Optical properties of fresh and frozen tissues of rat heart, kidney, brain, liver, and muscle were measured in the 450- to 700-nm range. The total reflectance and transmittance were measured using a well-calibrated integral sphere set-up. Absorption coefficient μa and reduced scattering coefficient μ's were derived from the experimental measurements using the inverse adding doubling technique. The influence of cryogenic processing on optical properties was studied. Interindividual and intraindividual variations were assessed. These new data aim at filling the lack of validated optical properties in the visible range especially in the blue-green region of particular interest for fluorescence and optogenetics preclinical studies. Furthermore, we provide a unique comparison of the optical properties of different organs obtained using the same measurement set-up for fresh and frozen tissues as well as an estimate of the intraindividual and interindividual variability.
Highlights
The use of biophotonics techniques has increased steadily in the last decade for both fundamental and preclinical research on small living animals
Monte Carlo simulations might be extremely useful for the design and optimization of instruments and experimental protocols in biophotonics, they need to be based on accurate optical properties of the tissues so that the conclusions drawn from the simulations are reliable
Inversion of the macroscopic measurement using inverse adding doubling (IAD) led to μa 1⁄4 1.09 cm−1 and μ 0s 1⁄4 9.06 cm−1 at 530 nm and μa 1⁄4 1.02 cm−1 and μ 0s 1⁄4 9.23 cm−1 at 630 nm, showing a good agreement with the optical properties measured by the manufacturer using the time resolved technique
Summary
The use of biophotonics techniques has increased steadily in the last decade for both fundamental and preclinical research on small living animals. Wide-field bioluminescence has become a standard for fast screening of small animal models of cancers in preclinical oncology.[1] In vivo optical imaging at the cellular level, such as two-photon fluorescence imaging, second harmonic generation imaging, or wide-field imaging techniques at the structure or organ level (intrinsic optical imaging, calcium or sensitive dye imaging), have become routine tools in labs,[2] especially in the neuroscience field. These techniques produce new data, unraveling structural and functional mechanisms, and have been adopted quickly as reference tools. Monte Carlo simulations based on simple and established algorithms for light propagation in tissues are commonly used to estimate these parameters, in order to properly design device and correctly interpret optical signals.[4,5] Monte Carlo simulations might be extremely useful for the design and optimization of instruments and experimental protocols in biophotonics, they need to be based on accurate optical properties of the tissues so that the conclusions drawn from the simulations are reliable
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