Ex Vivo Optical Properties Estimation for Reliable Tissue Characterization

Abstract

: Lasers are demonstrating high impact in many medical and biological applications. They have different interaction mechanisms within tissues depending on operational parameters, particularly the wavelength. In addition, the optical properties of the examined tissue (i.e., absorption and scattering properties) influence the efficacy of the applied laser. The development of optical biomedical techniques relies on the examination of tissues’ optical properties, which describe the viability of tissue optical evaluation and the effect of light on the tissue. Understanding the optical properties of tissues is necessary for the interpretation and evaluation of diagnostic data, as well as the prediction of light and energy absorption for therapeutic and surgical applications. Moreover, the accuracy of many applications, including tissue removal and coagulation, depends on the tissues' spectroscopic characteristics. In the current paper, a set of ex vivo absorption and scattering coefficients of different types of biological samples (skin, skull, liver and muscle) at 650 nm laser irradiation were retrieved using an integrating phere system paired with the Kubelka–Munk model. The obtained optical parameters were utilized to acquire the local fluence rate within the irradiated tissues based on the Monte Carlo simulation method and the diffusion approximation of the radiative transfer equation. The obtained results reveal that the optical absorption and scattering coefficients control the light propagation and distribution within biological tissues. Such an understanding refers to system design optimization, light delivery accuracy and the minimization of undesirable physiological effects such as phototoxicity or photobleaching.