The effect of vessel architecture on fusion by radio frequency current

Sealing and fusion of vessels by electrosurgical current is strongly influenced by the inhomogeneous architecture of the tissue constituents, particularly in the large arteries. Inhomogeneities in electrical properties of the constituents, specifically smooth muscle, collagen and elastin, lead to sharp spatial gradients in volumetric power deposition which results in uneven heating. The mechanical properties of the various tissue constituents are also of considerable importance. Vessel collagen and elastin distribution varies from vessel to vessel, species to species in the same artery, and point to point in the same vessel of the same animal or person. We present histologic evidence of vascular constituent variations, measurements of germane tissue electrical properties and numerical model studies of their effect on local heating rates and temperature rise in geometrically realistic finite difference vessel models. Comparisons between predicted and measured damage boundaries showed favorable agreement.