title: Monte Carlo method for photon heating using temperature-dependent optical properties.
abstract: The Monte Carlo method for photon transport is often used to predict the volumetric heating that an optical source will induce inside a tissue or material. This method relies on constant (with respect to temperature) optical properties, specifically the coefficients of scattering and absorption. In reality, optical coefficients are typically temperature-dependent, leading to error in simulation results. The purpose of this study is to develop a method that can incorporate variable properties and accurately simulate systems where the temperature will greatly vary, such as in the case of laser-thawing of frozen tissues. A numerical simulation was developed that utilizes the Monte Carlo method for photon transport to simulate the thermal response of a system that allows temperature-dependent optical and thermal properties. This was done by combining traditional Monte Carlo photon transport with a heat transfer simulation to provide a feedback loop that selects local properties based on current temperatures, for each moment in time. Additionally, photon steps are segmented to accurately obtain path lengths within a homogenous (but not isothermal) material. Validation of the simulation was done using comparisons to established Monte Carlo simulations using constant properties, and a comparison to the Beer-Lambert law for temperature-variable properties. The simulation is able to accurately predict the thermal response of a system whose properties can vary with temperature. The difference in results between variable-property and constant property methods for the representative system of laser-heated silicon can become larger than 100K. This simulation will return more accurate results of optical irradiation absorption in a material which undergoes a large change in temperature. This increased accuracy in simulated results leads to better thermal predictions in living tissues and can provide enhanced planning and improved experimental and procedural outcomes.
authors.affiliation: Bourns Hall A342, University of California, Riverside, Riverside, CA 92521, USA.
authors.forename: Adam Broadbent
authors.initials: AB
authors.lastname: Slade
authors.affiliation: Bourns Hall A345, University of California, Riverside, Riverside, CA 92521, USA. Electronic address: gaguilar@engr.ucr.edu.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Aguilar
mesh_terms: D006358:Hot Temperature; D009010:Monte Carlo Method; D055095:Optics and Photonics; D017785:Photons
keywords: Heat transfer; Laser heating; Monte Carlo; Optical irradiation; Photon transport; Temperature-dependent