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

When heated, living tissue exhibits random nonuniformities in temperature that are due to the discreteness of vessel arrangement. Because of the strong temperature dependence of the thermal coagulation rate these nonuniformities should substantially affect the necrosis growth induced by local heating. In the present work we study the effect of vessel discreteness on the form of a necrosis domain when its growth is limited by heat diffusion into the surrounding tissue. Namely, we analyze the characteristics of the necrosis boundary that are due to vessel discreteness. In particular, we find the mean amplitude δΓ and the correlation length lΓ of the necrosis boundary perturbations depending on the main tissue parameters. In addition, it is shown that there are universal relations between the mean size ℜ of the necrosis domain and the characteristics δΓ,lΓ of the boundary perturbations, which are due to the fractal structure of the vascular network. © 1999 Society of Photo-Optical Instrumentation Engineers.