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Finite element analysis of hepatic radiofrequency ablation probes using temperature-dependent electrical conductivity.

Chang I - Biomed Eng Online (2003)

Bottom Line: While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed.The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures.Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100 degrees C.

View Article: PubMed Central - HTML - PubMed

Affiliation: Office of Science and Technology, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Rockville, MD, USA. iac@cdrh.fda.gov

ABSTRACT

Background: Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed.

Methods: The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion.

Results: The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion.

Conclusion: Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100 degrees C.

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Electrical Conductivity as a Function of Source Voltage Figure demonstrates that larger sources are necessary to achieve the same electrical conductivity change in cases where tissue perfusion are accounted for.
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Figure 10: Electrical Conductivity as a Function of Source Voltage Figure demonstrates that larger sources are necessary to achieve the same electrical conductivity change in cases where tissue perfusion are accounted for.

Mentions: A major consequence of accounting for temperature-dependent phenomena is the large change in the electrical conductivity. Figures 9 and 10 show that the electrical conductivity change considerably when temperature-dependence is accounted for (128% without perfusion, 60% with perfusion). As seen in the results for current density, the electrical conductivity is explicitly related to temperature-dependent phenomena and implicitly related to tissue perfusion. Figure 11 shows the distribution of temperature-dependent electrical conductivity along the surface of the ablation probe. For the case where tissue perfusion is neglected, the center of the ablation probe is the area with the largest conductivity change. When tissue perfusion is accounted for, the areas corresponding to the proximal edge and the distal tip experience the most change. Figure 12 shows a three-dimensional representation of the temperature-dependent conductivity change with no perfusion. The figure shows a rapid decrease in the conductivity change in the radial direction.


Finite element analysis of hepatic radiofrequency ablation probes using temperature-dependent electrical conductivity.

Chang I - Biomed Eng Online (2003)

Electrical Conductivity as a Function of Source Voltage Figure demonstrates that larger sources are necessary to achieve the same electrical conductivity change in cases where tissue perfusion are accounted for.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC156890&req=5

Figure 10: Electrical Conductivity as a Function of Source Voltage Figure demonstrates that larger sources are necessary to achieve the same electrical conductivity change in cases where tissue perfusion are accounted for.
Mentions: A major consequence of accounting for temperature-dependent phenomena is the large change in the electrical conductivity. Figures 9 and 10 show that the electrical conductivity change considerably when temperature-dependence is accounted for (128% without perfusion, 60% with perfusion). As seen in the results for current density, the electrical conductivity is explicitly related to temperature-dependent phenomena and implicitly related to tissue perfusion. Figure 11 shows the distribution of temperature-dependent electrical conductivity along the surface of the ablation probe. For the case where tissue perfusion is neglected, the center of the ablation probe is the area with the largest conductivity change. When tissue perfusion is accounted for, the areas corresponding to the proximal edge and the distal tip experience the most change. Figure 12 shows a three-dimensional representation of the temperature-dependent conductivity change with no perfusion. The figure shows a rapid decrease in the conductivity change in the radial direction.

Bottom Line: While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed.The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures.Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100 degrees C.

View Article: PubMed Central - HTML - PubMed

Affiliation: Office of Science and Technology, Center for Devices and Radiological Health, U.S. Food and Drug Administration, Rockville, MD, USA. iac@cdrh.fda.gov

ABSTRACT

Background: Few finite element models (FEM) have been developed to describe the electric field, specific absorption rate (SAR), and the temperature distribution surrounding hepatic radiofrequency ablation probes. To date, a coupled finite element model that accounts for the temperature-dependent electrical conductivity changes has not been developed for ablation type devices. While it is widely acknowledged that accounting for temperature dependent phenomena may affect the outcome of these models, the effect has not been assessed.

Methods: The results of four finite element models are compared: constant electrical conductivity without tissue perfusion, temperature-dependent conductivity without tissue perfusion, constant electrical conductivity with tissue perfusion, and temperature-dependent conductivity with tissue perfusion.

Results: The data demonstrate that significant errors are generated when constant electrical conductivity is assumed in coupled electrical-heat transfer problems that operate at high temperatures. These errors appear to be closely related to the temperature at which the ablation device operates and not to the amount of power applied by the device or the state of tissue perfusion.

Conclusion: Accounting for temperature-dependent phenomena may be critically important in the safe operation of radiofrequency ablation device that operate near 100 degrees C.

Show MeSH