Tony Richard O. Almeida

Saline‐enhanced RF ablation on a cholangiocarcinoma: a numerical simulation

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 fin...

Using a tubular electrode for radiofrequency ablation: Numerical and experimental analysis

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.In the last two decades radiofrequency ablation (RFA) has been considered a promising medical procedure for the treatment of primary and secondary malignancies. However, the needle-based electrodes so far developed for this kind of treatment are not suitable for the thermal ablation of tumors located in hollow organs like esophagus, colon or bile duct. In this work a tubular electrode solution is presented. Numerical and experimental analyses were performed to characterize the volume of the lesion induced. Results show that this kind of electrode is a feasible solution and numerical simulation might provide a tool for planning RFA procedure with some accuracy.

Thermal ablation in biological tissue using tubular electrode

In the last decade, the study of methodologies for heating biological tissue has been an area of most interest in biology and medicine. As a result, the number of electrode solutions has grown in the past years. In this work, we study the capability of using a tubular electrode for heating biological tissue. To test this possibility, liver samples ex-vivo were used and numerical simulations were made. The final results were compared and revealed satisfactory and promising use of tubular electrodes for this kind of application.

Numerical modelling of magnetic induction heating of a tubular implant for hyperthermia procedures

In this paper it is studied the feasibility of using of a self-expandable stent, as an applicator for hyperthermia treatments by magnetic induction. This approach avoids the physical connection of the implant to a generator, and heat is generated from the interaction of the conductor with an applied external magnetic field. The latter induces a current in the section of the stent which, by Joule effect, will warm the adjacent tumour tissues. This study is carried considering a numerical simulation, based on finite element analysis, of a cholangiocarcinoma, a cancerous tumour located in the bile duct. Data obtained from this analysis have shown promising results, proving that it might be possible to induce thermal necrosis on the tissue adjacent to the implant. Still, the influence of major blood vessels next to the bile duct affect the temperature distribution and so the lesion volume might not be as uniform as expected.

Influence of slot geometry on air gap magnetic flux density of rotating machines

The objective of this work is to investigate the influence of slotted air gap constructive parameters on magnetic flux density of rotating machines. For this purpose, different approaches were used to solve the air gap field diagram using finite element method and the magnetic field distribution uniformity was evaluated by Carters factor calculation. Sensitivity analysis of slot constructive parameters was performed and results show that slot geometry modifies the magnetic flux on air gap and shifts the air gap magnetic equipotential midline of double slotted machines.

Modelling of a bipolar stent-based electrode for thermal radio frequency ablation of tumours located in hollow organs

Purpose – In this paper a numerical simulation analysis of a modified stent-based electrode is introduced to be used as a bipolar electrode for radio frequency ablation of tumours located in hollow organs. The purpose of this paper is to study the possibility of achieving a more regular volume of induced lesion with the presented electrode without imperilling the ductal organ where the tumour is located. Design/methodology/approach – Three types of bipolar electrode configurations were considered, formed by two, three and five tubular segments. Numerical simulations were performed considering a tumour located in the bile duct, where two important blood vessels – the portal vein and the hepatic artery – have a significant impact due to the convective heat transfer caused by the blood flow (heat sink effect) which significantly affects the shape of lesion that is intended to induce in order to destroy the tumour. Findings – The results obtained show that the five-segment electrode arrangement allows a regul...

Effects of the geometry of a tubular electrode on the temperature distribution in biologial tissue

Tubular electrodes provide a practicable way for heating biological tissues, suitable for medical and biological applications. This kind electrode is made from interlaced nitinol wires, forming a flexible tube that can be easily folded. This paper presents a study concerning the impact of the mesh density on tissue heating.

EasyMAG – magnetic field toolbox calculator for electrical installation project

Purpose – This paper aims to present a software application, called EasyMAG, for simulating and calculating the magnetic field during the design of domestic/industrial electrical installations.Design/methodology/approach – From a CAD software 3D representation of the model, including the electric wiring and considering the current in the electrical circuits, the software evaluates the magnetic field intensity for power‐line frequencies at different heights.Findings – Two application examples are presented consisting of a cabling layout in a lab room with three phase illumination and power socket circuits and a computer room above a power transformer room. The results were compared with measured values showing a good agreement between them.Originality/value – Shows that with this software it is possible to anticipate areas where magnetic field values might reach abnormally high values and to analyze alternative wiring layouts in order to keep the magnetic field values as low as possible.