Optical low-coherence reflectometry to enhance Monte Carlo modeling of skin

Optical low-coherence reflectometry and confocal microscopy images were taken of the rat dorsal skin flap window model. Blood vessel depths and diameters measured with the two techniques, and preparation thickness determined from reflectometry images, are in reasonable agreement with measurements from histologic sections. Blood vessels appear as areas of low signal when constant-depth reflectometry images are taken at a depth near the center of a vessel, whereas they appear bright when taken close to the blood-dermis boundary. Doppler shift plus increased light absorption in blood, and the blood-dermis index of refraction mismatch, are discussed as possible causes of the dark- and bright-appearing vessels, respectively. One reflectometry image was used to generate an input grid for a novel Monte Carlo analysis program that is capable of determining the light distribution and heat generation [J/m³] within complex blood vessel geometries. The feasibility of imaging skin blood vessel accurately with optical low-coherence tomography, and using the acquired knowledge of blood vessels structure to create more realistic Monte Carlo analyses is demonstrated by the results of the study.