Abstract (Summary)
This study describes a detailed methodology for modeling three-dimensional radiofrequency (rf) ablation using a reconstructed vasculature geometry. MRI images of a sectioned liver tissue containing arterial vessels are processed and converted into a finite-element mesh. Convective cooling within large vessels is treated using direct physical modeling of the heat and momentum transfer within the vessel. Perfusion within the smaller vessels is modeled using a porous medium. This direct-simulation approach allows for treatment of rf heating of tumors located near large vessels, which is problematic for approaches which handle perfusion using a lumped heat-transfer coefficient. An rf heat source in the form of a spherically symmetric Gaussian distribution, fit from a previously computed profile, as well as electrical heat source, are employed. Computations of temperature rise were performed for transient rf procedures in the case where the tumor is located near the bifurcation point of a hepatic artery. Results demonstrate a significant effect due to convective cooling by the large vessels. The effect of heat convection through the nearby arteries and elevated level of blood perfusion through the tissue reduced the steady state peak temperature by about 27%. In relation to the width of the heat source, the peak temperature shifted by about 20%. Substantial asymmetries in the temperature profiles indicate ablation procedures that may achieve adequate tumor destruction in some regions, but that elevate the temperature only minimally in other regions, thereby permitting possible tumor recursion. These critical features of the temperature field are due to the directional nature of the arterial flow, and are difficult to capture with models that treat perfusion with a scalar source term in the bioheat equation.
Bibliographical Information:


School:University of Cincinnati

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:radio frequency thermal ablalion pennes bioheat transfer equations image reconstruction hepatic tumor blood flow effect on heat in porous tissue


Date of Publication:01/01/2003

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