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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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Related in: MedlinePlus

Heat Flux as a Function of Source Voltage The figure demonstrates that both temperature-dependant phenomena and tissue perfusion affect the heat flux.
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Figure 16: Heat Flux as a Function of Source Voltage The figure demonstrates that both temperature-dependant phenomena and tissue perfusion affect the heat flux.

Mentions: Figure 15 presents a comparison of the heat flux for the four models when a source voltage of 20.0 volts is applied. In each case, the heat flux is greatest at the proximal edge and the distal tip of the ablation probe. The data show that accounting for perfusion decreases the heat flux by 4%. Accounting for temperature-dependent electrical conductivity increases the heat flux by approximately 11%. This demonstrates that temperature-dependent phenomena dominate the changes that occur in the heat sink (Figure 16).


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

Chang I - Biomed Eng Online (2003)

Heat Flux as a Function of Source Voltage The figure demonstrates that both temperature-dependant phenomena and tissue perfusion affect the heat flux.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 16: Heat Flux as a Function of Source Voltage The figure demonstrates that both temperature-dependant phenomena and tissue perfusion affect the heat flux.
Mentions: Figure 15 presents a comparison of the heat flux for the four models when a source voltage of 20.0 volts is applied. In each case, the heat flux is greatest at the proximal edge and the distal tip of the ablation probe. The data show that accounting for perfusion decreases the heat flux by 4%. Accounting for temperature-dependent electrical conductivity increases the heat flux by approximately 11%. This demonstrates that temperature-dependent phenomena dominate the changes that occur in the heat sink (Figure 16).

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
Related in: MedlinePlus