Simulation study of the cooling effect of blood vessels and blood coagulation in hepatic radio-frequency ablation

Nikhil Vaidya (Corresponding author), Marco Baragona, Valentina Lavezzo, Ralph Maessen, Karen Veroy

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Abstract

Purpose
Computer simulations of hepatic radio-frequency ablation (RFA) were performed to: (i) determine the dependence of the vessel wall heat transfer coefficient on geometrical parameters; (ii) study the conditions required for the occurrence of the directional effect of blood; and (iii) classify blood vessels according to their effect on the thermal lesion while considering blood coagulation. The information thus obtained supports the development of a multi-scale bio-heat model tailored for more accurate prediction of hepatic RFA outcomes in the vicinity of blood vessels.

Materials and methods
The simulation geometry consisted of healthy tissue, tumor tissue, a mono-polar RF-needle, and a single cylindrical blood vessel. The geometrical parameters of interest were the RF-needle active length and those describing blood vessel configuration. A simple, novel method to incorporate the effects of blood coagulation into the simulation was developed and tested.

Results
A closed form expression giving the dependence of the vessel wall heat transfer coefficient on geometrical parameters was obtained. Directional effects on the thermal lesion were found to occur for blood vessel radii between 0.4 mm and 0.5 mm. Below 0.4 mm blood coagulation blocked the flow.

Conclusions
The closed form expression for the heat transfer coefficient can be used in models of RFA to speed up computation. The conditions on vessel radii required for the occurrence of directional effects on the thermal lesion were determined. These conditions allow the classification of blood vessels. Different approximations to the thermal equation can thus be used for these vessel classes.
Original languageEnglish
Pages (from-to)95-104
Number of pages10
JournalInternational Journal of Hyperthermia
Volume38
Issue number1
DOIs
Publication statusPublished - 2 Feb 2021

Keywords

  • Nusselt number
  • Radio-frequency ablation
  • blood coagulation
  • directional effect
  • modeling

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