Computational modeling of radiofrequency ablation with an internally cooled wet electrode
A finite element model of radiofrequency tumor ablation with an internally cooled wet electrode was built and its computer results were compared to those reported in a clinical study involving 17 patients with hepatocellular carcinoma. The model whose res
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Abstract: A finite element model of radiofrequency tumor ablation with an internally cooled wet electrode was built and its computer results were compared to those reported in a clinical study involving 17 patients with hepatocellular carcinoma. The model whose results best matched the clinical results was based on three compartments and assumed a hydrated tumor: computed transversal diameter of 39.2 mm vs. reported diameter of 33.7 ± 7.1 mm. The impedances of the model (47.9 Ω) and the clinical trials (46 ± 6 Ω) were also similar, both at 140 W. The results showed the advantage of a three-compartment over a two-compartment model when simulating the real effects of treatment on cancerous tissue. Keywords: radiofrequency ablation, internally cooled wet electrode, hepatocellular carcinoma, computational modeling
performance. As far as we know there exist few computational studies on ICW [3]–[5], and none has considered the tumor or tried to define saline distribution inside the tissue. We therefore built a computational model of HCC radiofrequency ablation with an ICW electrode. The modeling study included three compartments (tumor, tissue and saline irrigated tumor). The saline distribution employed in the model was estimated from an in vivo study on porcine liver and the clinical outcome of a previous study was used to validate the computational results. Our aim was to assess the influence of considering the tumor and hydrated tissue in the ICW computational model.
II. I.
METHODS
INTRODUCTION A. Computational model
Hepatocellular carcinoma (HCC) is the 5th most frequently encountered malignancy and has the second highest cancer mortality rate. Radiofrequency ablation (RFA) is a procedure widely employed to treat HCC smaller than 3 cm in size. However, the main issue still lies in the high number of cases with difficult-to-treat tumors larger than 3 cm. One of the techniques proposed to overcome this limitation is the use of internally cooled wet electrodes (ICW) based on a system of hydration of the adjacent tissue with hypertonic saline (20% NaCl) and simultaneous internal cooling of the electrode. ICW electrodes prevent tissue from vaporizing and charring, increase its electrical conductivity and improve power deposition in the tissue, which extends the time before the abrupt rise in impedance (roll-off). The fully dehydrated tissue surrounding the electrode has a marked tendency to cause roll-off [1]. It is also known that there is an optimal distance from the saline infusion to prevent dehydration and enlarge the coagulation zone [2]. Rapid and low-cost computational models can play a vital role in optimizing clinical findings in this field and more realistic models are necessary to improve ICW electrode
© Springer Nature Singapore Pte Ltd. 2018 H. Eskola et al. (eds.), EMBEC & NBC 2017, IFMBE Proceedings 65, DOI: 10.1007/978-981-10-5122-7_267
The computational model encompassed the RFA of an HCC tumor with an ICW electrode (Fig. 1a). The problem was solved by a finite element analysis. As shown in
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