Modeling laser irradiation conditions for mucosal tissues in antimicrobial photodynamic therapy

Abstract

We use computer modeling to analzye empirically selected conditions for antimicrobial photodynamic therapy of mucosal tissues. We calculate the optical and thermal fields for experimental conditions for low-intensity (cold) laser irradiation used in treatment of lesions in mucosal tissues stained by methylene blue: λ = 670 nm, power density 150–300 mW/cm2, doses 9–18 J/cm2; λ = 632.8 nm, 15 mW/cm2, dose 4.5 J/cm2. For numerical estimates, we used the optical characteristics of methylene blue and three layers of mucosal tissues at the laser radiation wavelengths, and also the thermal characteristics of the tissues. The experimental conditions were optimized using the ratio of the tissue penetration depth for the absorbed optical energy and the penetration depth of methylene blue into the lesion, while maintaining safe tissue heating temperatures.