Radiofrequency (RF) ablation can be delivered percutaneously to hepatic tumors in a minimally invasive manner. The major limitation of RF ablation has been a high post- treatment local tumor recurrence rate. The most troublesome reason for the high local recurrence rate associated with RF, the inability of RF to destroy all tumor cells within a zone targeted for ablation, is the focus of this proposal. Preliminary finite element modeling (FEM) of a commonly used RF device has suggested that tumor cells within an RF lesion, but adjacent to vessels, were not heated to lethal temperatures. We have developed an implantable in vivo animal model of solitary liver metastasis. In this model RF ablation sometimes yielded incomplete tumor cell death within the RF lesion. We therefore hypothesize that RF, as currently delivered, does not kill all tumor cells within a lesion. We propose to develop FEMs of RF ablation that predict current and temperature distribution in hepatic tumors. These models will incorporate RF catheter specifications, thermal convection (effect of blood flow), tissue resistivities, and tissue thermal conductivities. Commercially available devices will be modeled and the results confirmed in both a solitary metastasis model, and a model of tumor adjacent to large vessels. We further hypothesize that FEM can be utilized to design better RF devices and procedures, and thus optimize cell death. RF delivered by new electrode designs, at different frequencies, and via multiple devices will be modeled. Biomedical engineers will focus on the FEM and construction of different RF probe systems utilizing electrical resistivity data and thermal tissue properties. When a promising design is found, in vivo experiments to validate the mathematical model will be performed. The team we have formed is uniquely poised to address the clinical problem of ineffective RF ablation. Using these data, new RF units can be designed to overcome the limitations of currently available RF ablation systems.
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