Purpose -Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to carcinomas. Besides its mechanical application, SEMS can be regarded as well as potential electrode for performing RF ablation therapy on the tumor. The purpose of this work is to perform numerical and experimental analyses in order to characterize the lesion volume induced in biological tissue using this kind of tubular electrode. Design/methodology/approach -Data concerning electrical conductivity and dimension of the damaged tissue after RF ablation procedure were obtained from ex vivo samples. Next, numerical models using 3D finite element method were obtained reassembling the conditions considered at experimentation setup and results were compared. Findings -Numerical and experimental results show that a regular volume of damaged tissue can be obtained considering this type of electrode. Also, results obtained from numerical simulation are close to those obtained by experimentation. Originality/value -SEMSs, commonly used as devices to minimize obstruction problems due to the growth of tumors, may still be considered as an active electrode for RF ablation procedures. A method considering this observation is presented in this paper. Also, numerical simulation can be regarded in this case as a tool for determining the lesion volume.

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Purpose -Cholangiocarcinoma is an adenocarcinoma of the bile ducts which drain bile from the liver into the small intestine. Unfortunately, most patients are diagnosed at an advanced stage of the disease with almost no chances for surgery, the only potentially curative treatment. As nitinol stents can be used to reduce stricture problems of the bile duct, these can be also considered as potential electrodes for hyperthermia treatments. Previous works show that, in fact, these metallic stents might be used as part of a feasible solution for delivering radiofrequency (RF) energy into a tumor located in a hollow organ to destroy the tumor tissue. However, the tissue lesion induced is not completely uniform due to convective heat transfer associated to the blood flow in the nearby vessels. The purpose of this paper is to study the use of saline solution for modifying the electrical conductivity of the tissue in order to obtain a more uniform lesion. Design/methodology/approach -A numerical analysis using finite element method on a simplified model of the porta hepatis is performed. The tumor tissue is divided in three sections and simulations were performed considering a higher electrical conductivity in the middle section of the tumor, imitating the presence of a saline solution in this part of the tissue. Findings -Results show that it is possible to obtain a more regular volume, by the way the tumor tissue is preferentially heated, although there are still some risks on exceeding the dimension of the bile duct. Originality/value -This study presents the numerical analysis of a saline-enhanced RF tissue thermoablation of a cholangiocarcinoma considering a stent-based electrode. Results point to the possibility of obtaining a more regular volume of damaged tissue in order to heat and preferentially destroy the tumor tissue.

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