Effect of blood vessel discreteness on necrosis formation during laser induced thermal coagulation limited by heat diffusion

When heated, living tissue exhibits random nonuniformities in temperature t hat are due to the discreteness of vessel arrangement. Because of the stron g temperature dependence of the thermal coagulation rate these nonuniformit ies should substantially affect the necrosis growth induced by local heatin g. In the present work we study the effect of vessel discreteness on the fo rm of a necrosis domain when its growth is limited by heat diffusion into t he surrounding tissue. Namely, we analyze the characteristics of the necros is boundary that are due to vessel discreteness. In particular, we find the mean amplitude delta(Gamma) and the correlation length l(Gamma) of the nec rosis boundary perturbations depending on the main tissue parameters. In ad dition, it is shown that there are universal relations between the mean siz e R of the necrosis domain and the characteristics delta(Gamma), l(Gamma) o f the boundary perturbations, which are due to the fractal structure of the vascular network, (C) 1999 Society of Photo-Optical Instrumentation Engine ers. [S1083-3668(99)00702-9].