A model for optical and thermal analysis of laser balloon angioplasty

Laser balloon angioplasty is modeled using an infinitely long, axisymmetric cylinder. The balloon surface is assumed to be uniformly irradiated by diffuse light at 1060 nm delivered from within the balloon core. The diffusion approximation to the radiative transport equation is solved for a single-layer homogeneous medium enclosing the transparent fluid-filled balloon. The computed light fluence rate (W-cm ^-2) just beneath the tissue surface is 4.7 times the primary irradiance, owing to scattering and secondary irradiance from the integrating cylinder effect of light backscattered into the inner core. The transient temperature response of the heated tissue is then calculated using an implicit finite-difference solution of the heat conduction equation for concentric layers of varying thermal properties. The extent of damage is analyzed using the Arrhenius rate process model. Changes in optical and thermal properties with temperature and thermal phase transitions have been omitted in all of the analyses.