Estimation of optical parameters and fluence rate distribution in biological tissues via a single integrating sphere optical setup

Abstract Optical parameters of biological tissues play an important role in tissue characterization, including the absorption and scattering coefficients and the anisotropy factor. These parameters are high wavelength dependent and give functional information of the tissue such as total haemoglobin content, tissue oxygenation and water fraction. However, estimating the optical properties of any tissue requires measurements of diffuse reflectance, diffuse transmittance and collimated transmittance. Experimentally, these measurements can be obtained either by integrating spheres techniques or with methods that based on distant detectors array. In this work, total diffuse reflectance and transmittance of native and dry chicken breast skin were measured in vitro via a single integrating sphere optical setup at 660 and 808 nm laser irradiation. Then, a combination between Kubellka-Munk model and Bouguer-Beer-Lambert law was used to estimate the three optical parameters from the collected data. The calculated optical parameters were then introduced to the diffusion equation to compute the optical fluence rate distribution at the boundary of the sample using the finite element method. The Monte-Carlo simulation method was implemented for validation showing absolute error of 0.002 and 0.009 at 660, 808 nm respectively for normal skin, 0.0013, and 0.0078 in dry skin.