15 February 2013 Monte Carlo simulation of radiation transfer in human skin with geometrically correct treatment of boundaries between different tissues
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Abstract
In customary implementation of three-dimensional (3D) Monte Carlo (MC) numerical model of light transport in heterogeneous biological structures, the volume of interest is divided into voxels by a rectangular spatial grid. Each voxel is assumed to have homogeneous optical properties and curved boundaries between neighboring tissues inevitably become serrated. This raises some concerns over realism of the modeling results, especially with regard to reflection and refraction on such boundaries. In order to investigate the above concern, we have implemented an augmented 3D MC code, where tissue boundaries (e.g., blood vessel walls) are defined by analytical functions and thus maintain their shape regardless of grid discretization. Results of the customary and augmented model are compared for a few characteristic test geometries, mimicking a cutaneous blood vessel irradiated with a 532 nm laser beam of finite diameter. Our analysis shows that at specific locations inside the vessel, the amount of deposited laser energy can vary between the two models by up to 10%. Even physically relevant integral quantities, such as linear density of the energy absorbed by the vessel, can differ by as much as 30%. Moreover, the values obtained with the customary model vary strongly with discretization step and don’t disappear with ever finer discretization. Meanwhile, our augmented model shows no such behavior, indicating that the customary approach suffers from inherent inaccuracies arising from physically flawed treatment of tissue boundaries.
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Jan Premru, Jan Premru, Matija Milanič, Matija Milanič, Boris Majaron, Boris Majaron, Luka Vidovic, Luka Vidovic, } "Monte Carlo simulation of radiation transfer in human skin with geometrically correct treatment of boundaries between different tissues", Proc. SPIE 8579, Optical Interactions with Tissue and Cells XXIV, 85790Z (15 February 2013); doi: 10.1117/12.2003672; https://doi.org/10.1117/12.2003672
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