Light distributions in artery tissue: Monte Carlo simulations for finite‐diameter laser beams

Finite‐width light distributions in arterial tissue during Argon laser irradiation (476 nm) are simulated using the Monte Carlo method. Edge effects caused by radial diffusion of the light extend ±1.5 mm inward from the perimeter of a uniform incident beam. For beam diameters exceeding 3 mm the light distribution along the central axis can be described by the one‐dimensional solution for an infinitely wide beam. The overlapping edge effects for beam diameters smaller than 3 mm reduce the penetration of the irradiance in the tissue. The beam profile influences the light distribution significantly. The fluence rates near the surface for a Gaussian beam are two times higher on the central axis and decrease faster radially than for a flat profile. The diverging light from a fiber penetrates tissue in a manner similar to collimated light.