Search results

The purpose of this paper is to enable the correct selection of the radiofrequency thermal ablation (RFTA) process parameters for an individual patient by applying a computer modelling of RFTA.

The model is based on the X‐ray computer tomography images of the primary and metastatic hepatic tumours. The authors used the professional package of FLUX3D to generate the geometric models, assign materials properties, assign boundary conditions, perform mesh, carry out coupled thermo‐electromagnetic analysis and for post processing. The distribution of temperature and electric potential in the tissues of tumour and liver had been obtained as main results of the calculations.

The computational results show that the RFTA algorithm is effective in solving this practical problem. The computational results show that the selection of the type of electrodes used in the RFTA process is as important as the correct selection of the process parameters, i.e. voltage and frequency.

The paper presents a method to simulate the RFTA process and to select the process parameters.

The purpose of this paper is to propose a planning strategy for the radio frequency ablation (RFA) treatment of hepatic tumors. The goal is to give to the surgeon the opportunity of controlling the shape and the size of the treated volume and preserving the healthy tissues.

A FEM model of the human torso is built from radiographic and MRI scans of the patients, and then the RFA treatment “dynamically optimized” by controlling currents in multiple external electrodes, in such a way to drive currents in the desired regions, burning the tumor while trying to preserve healthy regions. A suitable cellular death model is considered in order to achieve an effective description of the biological modifications in the tumor volume.

A numerical method to plan the RFA treatment of hepatic tumors has been defined, aiming to preserve as much as possible healthy tissues.

The method depends on the knowledge of inner structure and properties of the patient's torso; while the structure of tissues can be determined by TAC or MRI scans, the physiological properties are much more uncertain.

The proposed approach allows optimized RFA treatments to be designed, allowing reduction of damage to healthy tissues deriving from application of the treatment.

The problem of optimal design of RFA treatments has been previously tackled in literature, but in this paper, dynamical optimization techniques and a cell death rate model have been included.

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.

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.

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.

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 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.

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.

The results obtained show that the five-segment electrode arrangement allows a regular volume for the induced lesion, independently of the different values of applied voltage considered.

The presented work introduces a numerical simulation analysis on a modified based-stent electrode previously studied. In this case, the electrode is configured so it can be used as a bipolar electrode, i.e., active and ground electrode are placed in the same device. Besides the results evinced by the obtained results, this kind of electrode avoids eventual skin burns that might occur due to the need of the return electrodes when monopolar electrodes are used.

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.

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.

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.

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.

The purpose of this paper is to study haemodynamic flow characteristics and entropy analysis in a bifurcated artery system subjected to stenosis, magnetohydrodynamic (MHD) flow and aneurysm conditions. The findings of this study offer significant insights into the intricate interplay encompassing electro-osmosis, MHD flow, microorganisms, Joule heating and the ternary hybrid nanofluid.

The governing equations are first non-dimensionalised, and subsequently, a coordinate transformation is used to regularise the irregular boundaries. The discretisation of the governing equations is accomplished by using the Crank–Nicolson scheme. Furthermore, the tri-diagonal matrix algorithm is applied to solve the resulting matrix arising from the discretisation.

The investigation reveals that the velocity profile experiences enhancement with an increase in the Debye–Hückel parameter, whereas the magnetic field parameter exhibits the opposite effect, reducing the velocity profile. A comparative study demonstrates the velocity distribution in Au-CuO hybrid nanofluid and Au-CuO-GO ternary hybrid nanofluid. The results indicate a notable enhancement in velocity for the ternary hybrid nanofluid compared to the hybrid nanofluids. Moreover, an increase in the Brinkmann number results in an augmentation in entropy generation.

This study investigates the flow characteristics and entropy analysis in a bifurcated artery system subjected to stenosis, MHD flow and aneurysm conditions. The governing equations are non-dimensionalised, and a coordinate transformation is applied to regularise the irregular boundaries. The Crank–Nicolson scheme is used to model blood flow in the presence of a ternary hybrid nanofluid (Au-CuO-GO/blood) within the arterial domain. The findings shed light on the complex interactions involving stenosis, MHD flow, aneurysms, Joule heating and the ternary hybrid nanofluid. The results indicate a decrease in the wall shear stress (WSS) profile with increasing stenosis size. The MHD effects are observed to influence the velocity distribution, as the velocity profile exhibits a declining nature with an increase in the Hartmann number. In addition, entropy generation increases with an enhancement in the Brinkmann number. This research contributes to understanding fluid dynamics and heat transfer mechanisms in bifurcated arteries, providing valuable insights for diagnosing and treating cardiovascular diseases.

Recently, the porous media theory has been successively proposed for many bioengineering applications. The purpose of this paper is to analyze if the porous media theory can be applied to model radiofrequency (RF) cardiac ablation.

Blood flow, catheter and tissue are modeled. The latter is further divided into a fluid and a solid phase, and porous media equations are used to model them. The heat source term is modeled using the Laplace equation, and the finite element method is used to solve the governing equations under the appropriate boundary conditions and closure coefficients.

After validation with available literature data, results are shown for different velocities and applied voltages to understand how these parameters affect temperature fields (and necrotic regions).

The model might require further validation with experiments under different conditions after comparisons with available literature. However, this might not be possible due to the experimental complexity.

The improvement in predictions from the model might help the final user, i.e. the surgeon, who uses cardiac ablation to treat arrhythmia.

This is the first time that the porous media theory is applied to RF cardiac ablation. The robustness of the model, in which many variables are taken into account, makes it suitable to better predict temperature fields, and damaged regions, during RF cardiac ablation treatments.

This paper aims to summarize the radiological interventions that can be used by obstetricians and gynecologists.

E-health systems apply in all hospital sectors in the world; interventional radiology (IR) now includes transcatheter and percutaneous techniques that can be applied to various organ systems, including the female reproductive system and pelvis. Interventional radiologists can now offer many services to obstetricians and gynecologists. With the advent of new procedures and refinement of existing techniques, there are now a number of procedures that can be used to treat both vascular and non-vascular diseases. This review summarizes the radiological interventions that can be used by obstetricians and gynecologists.

This review is intended to help gynecologists and obstetricians understand the role of IR in their specialty. Many valuable vascular and nonvascular interventional services can be provided by radiologists for both obstetric and gynecological indications. Many of these IR procedures are minimally invasive with less risk to the patients.

IR is now being used to treat some conditions encountered in obstetrics and gynecology, in particular, uterine leiomyomas, placenta accreta, postpartum hemorrhage and pelvic congestion syndrome. Moreover, with the help of IR, radiologists can also manage several nonvascular pathologies, including drainage of pelvic abscesses, fallopian tube recanalization, image-guided biopsy and fluid collections involving ovarian lesions. The major challenges faced when performing obstetric IR procedures are reduction of radiation exposure for the patient and fetus and preservation of fertility. This review highlights the role of IR in the treatment of various vascular and nonvascular pathologies encountered in obstetrics and gynecology.

The purpose of this study is to show that the methods of the numerical simulation can be a very effective tool for a proper choice of control parameters of artificial hyperthermia. An electromagnetic field induced by two external electrodes and a temperature field resulting from electrodes action in a 3D domain of biological tissue is considered. An important problem is the appropriate directing of heat in the region of tumor, so as to avoid damaging healthy cells surrounding the tumor. Recently, to concentrate the heat on the tumor, magnetic nanoparticles, which are introduced into the tumor, were used. The nanoparticles should be made of material that ensures appropriate magnetic properties and has a high biocompatibility with the biological tissue. External electric field causes the heat generation in the tissue domain.

The distribution of electric potential in the domain considered is described by the Laplace system of equations, while the temperature field is described by the Pennes’ system of equations. These problems are coupled by source function being the additional component in the Pennes’ equation and resulting from the electric field action. The boundary element method is applied to solve the coupled problem connected with the heating of biological tissues.

The aim of investigations is to determine an electric potential of external electrodes and the number of nanoparticles introduced to a tumor region to obtain the artificial hyperthermia state. The tests performed showed that the proposed tool to solve the inverse problem provides correct results.

In the paper the steady state bioheat transfer problem is considered, so the thermal damage is a function of the temperature only. Therefore, the solution can be considered as the maximum ablation zone of cancer. Additionally, the choice of appropriate parameters will be affected on the position and shape of the tumor and the electrodes.

In the paper the inverse problem has been solved using the evolutionary algorithm, gradient method and hybrid algorithm which is a combination of the two previous.

Gives a bibliographical review of the finite element methods (FEMs) applied in biomedicine from the theoretical as well as practical points of view. The bibliography at the end of the paper contains 748 references to papers, conference proceedings and theses/dissertations dealing with the finite element analyses and simulations in biomedicine that were published between 1985 and 1999.