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TECHNICAL PAPERS: Fluids/Heat/Transport

# Radio-Frequency Ablation in a Realistic Reconstructed Hepatic Tissue

[+] Author and Article Information
Prasanna Hariharan

Graduate Student Mechanical Engineering Department, University of Cincinnati, 688 Rhodes Hall, P.O. Box 210072, Cincinnati, OH 45221-0072

Isaac Chang

Biomedical Engineer Division of Physics, Center for Devices and Radiological Health, US Food and Drug Administration, 10903 New Hampshire Avenue, Building 62, Silver Spring, MD 20993-0002

Matthew R. Myers

Research Physicist Division of Solid and Fluid Mechanics, Center for Devices and Radiological Health, US Food and Drug Administration, 10903 New Hampshire Avenue, Building 62, Silver Spring, MD 20993-0002

Rupak K. Banerjee1

Associate Professor Mechanical Engineering Department, 688 Rhodes Hall, University of Cincinnati, PO Box 210072 Cincinnati, OH 45221-0072rupak@banerjee@uc.edu

1

Corresponding author.

J Biomech Eng 129(3), 354-364 (Nov 19, 2006) (11 pages) doi:10.1115/1.2720912 History: Received March 18, 2006; Revised November 19, 2006

## Abstract

This study uses a reconstructed vascular geometry to evaluate the thermal response of tissue during a three-dimensional radiofrequency (rf) tumor ablation. MRI images of a sectioned liver tissue containing arterial vessels are processed and converted into a finite-element mesh. A rf heat source in the form of a spherically symmetric Gaussian distribution, fit from a previously computed profile, is employed. Convective cooling within large blood vessels is treated using direct physical modeling of the heat and momentum transfer within the vessel. Calculations of temperature rise and thermal dose are performed for transient rf procedures in cases where the tumor is located at three different locations near the bifurcation point of a reconstructed artery. Results demonstrate a significant dependence of tissue temperature profile on the reconstructed vasculature and the tumor location. Heat convection through the arteries reduced the steady-state temperature rise, relative to the no-flow case, by up to 70% in the targeted volume. Blood flow also reduced the thermal dose value, which quantifies the extent of cell damage, from $∼3600min$, for the no-flow condition, to $10min$ for basal flow $(13.8cm∕s)$. Reduction of thermal dose below the threshold value of $240min$ indicates ablation procedures that may inadequately elevate the temperature in some regions, thereby permitting possible tumor recursion. These variations are caused by vasculature tortuosity that are patient specific and can be captured only by the reconstruction of the realistic geometry.

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Copyright © 2007 by American Society of Mechanical Engineers
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## Figures

Figure 3

Gaussian-distributed RF heat source. The Gaussian heat source in W∕m3 is plotted along the y axis.

Figure 4

Temperature contours within the tumor zone, in the x-z plane at time t=20min for arterial velocities 1cm∕s and 13.8cm∕s

Figure 1

MRI images of the excised porcine liver cross section shown in (A) and (B), provided by Jan Johannessan (Food and Drug Administration, Rockville, MD)

Figure 2

Reconstructed bifurcated arteries with surrounding hepatic tissues are shown in different planes. The RF ablation probe is inserted in the spherical tumor domain, considered to be the ablation zone.

Figure 5

Temperature rise within the tumor as a function of x, y, and z axis distances at time t=20min for tumor location-1. z=0 denotes tumor center. Arterial velocities are 0cm∕s, 1cm∕s, and 13.8cm∕s. #1=lower tumor boundary close to the bifurcation region; #2=upper tumor boundary away from the bifurcation region.

Figure 6

Temperature rise within the tumor as a function of x, y, and z axis distances at time t=20min for tumor location-2. z=0 denotes tumor center. Arterial velocities are 0cm∕s, 1cm∕s, and 13.8cm∕s. #1=peak temperature rise location.

Figure 7

Temperature rise within the tumor as a function of x, y, and z axis distances at time t=20min for tumor location-3. z=0 denotes tumor center. Arterial velocities are 0cm∕s, 1cm∕s, and 13.8cm∕s. #1=peak temperature rise location, #2=tumor boundary located close to main branch of the artery, and #3=tumor boundary located away from main branch of the artery.

Figure 8

Temperature time history along the outer surface of the tumor located near the bifurcation point (location-1). Arterial velocities are 0cm∕s, 1cm∕s, and 13.8cm∕s. #1, #2, #3=time at which the temperature rise attains 80% of the steady state value.

Figure 9

Thermal dose values as a function of artery inlet velocities (1cm∕s and 13.8cm∕s) at z=±7mm and x=±7mm

Figure 10

Temperature plots along y and z direction for three different conditions (a) no convection and scalar perfusion (b) u=13.8cm∕s as inlet velocity including vector perfusion and (c) u=13.8cm∕s as inlet velocity including vector perfusion

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