Can CW Nd: YAG Photocoagulation Lesion Dimensions in Myocardium Be Predicted By Monte Carlo Light Propagation Simulations?

Light dosimetry may be a helpful tool for predicting lesion dimensions achieved by Nd:YAG laser photocoagulation of myocardium in two experimental groups: non-contact laser irradiation with a 5-mm spot size (group I); contact 400- mu m fiber (group II). Monte Carlo-simulated radiant intensity models were generated for normal (A) and photocoagulated (B) tissue optical parameters. The histological lesion depth (D) and radius (r) showed a linear increase with laser output, both in groups I and II. Heuristic results of the lesion dimensions and the tissue local radiant intensity isodoses ( omega ) were as follows (R is correlation coefficient): group I A & B - Lesion depth showed no acceptable fit; IA - r = 0.9 + 470/ omega , R = 0.8; IB - r = 2 + 310/ omega , R = 0.85; IIA - D = 4 + 200/ omega , R = 0.89; IIB - D = 3.5 + 118/ omega , R = 0.92; IIA - r = 4 + 400/ omega , R = 0.5; IIB - r = 3.5 + 250/ omega , R = 0.7. Exponential regression analyses did not present significant statistical improvements. Because of the wide spread in experimental data, a single general predicting formula could not be derived.