Mathematical modeling of radiofrequency ablation during open-heart surgery (original) (raw)
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Medical & Biological Engineering & Computing, 2000
AbstractÐFinite element (FE) analysis has been utilised as a numerical tool to determine the temperature distribution in studies of radio frequency (RF) cardiac ablation. However, none of the previous FE analyses clari®ed such computational aspects as software requirements, computation time or convergence test. In addition, myocardial properties included in the previous models vary greatly. A process of FE modelling of a system that included blood, myocardium, and an ablation catheter with a thermistor embedded at the tip is described. The bio-heat equation is solved to determine the temperature distribution in myocardium using a commercial software application (ABAQUS). A Cauchy convergence test (E 0X1 C) was performed and it is concluded that the optimal number of elements for the proposed system is 24610. The effects of changes in myocardial properties ( AE 50% electric conductivity, 100%aÀ50% thermal conductivity, and 100%aÀ50% speci®c heat capacity) in both power-controlled (PCRFA) and temperature-controlled RF ablation (TCRFA) were studied. Changes in myocardial properties affect the results of the FE analyses of PCRFA more than those of TCRFA, and the maximum changes in lesion volumes were À58.6% (À50% electric conductivity), À60.7% (100% thermal conductivity), and 43.2% (À50% speci®c heat).
The open biomedical engineering journal, 2012
Radiofrequency cardiac ablation (RFCA) has been used to treat certain types of cardiac arrhythmias by producing a thermal lesion. Even though a tissue temperature higher than 50ºC is required to destroy the target, thermal mapping is not currently used during RFCA. Our aim was thus to develop mathematical models capable of estimating tissue temperature from tissue characteristics acquired or estimated at the beginning of the procedure (electrical conductivity, thermal conductivity, specific heat and density) and the applied voltage at any time. Biological tissue was considered as a system with an input (applied voltage) and output (tissue temperature), and so the mathematical models were based on transfer functions relating these variables. We used theoretical models based on finite element method to verify the mathematical models. Firstly, we solved finite element models to identify the transfer functions between the temperature at a depth of 4 mm and a constant applied voltage usi...
2010
Radiofrequency ablation has been used to treat some types of cardiac arrhythmias. We have previously proposed an ARMAX model (non structural) to estimate the temperature in the tissue during ablation. Computer modeling has allowed us to study the temperature distribution by means of solving numerically theoretical models based on partial differential equations, which represent physical phenomena. Now, our objective is to consider the biological tissue as a system with an input (applied voltage) and output (tissue temperature), and search for a transfer function between these variables. The final aim is to have a simple model that could estimate the temperature at each point of the tissue. We solved the model using the finite element method and identified the transfer function between the temperature at 4 mm depth and an applied voltage using a 7Fr and 4 mm electrode. We used COMSOL Multiphysics to solve the electro-thermal problem and MATLAB to obtain the transfer function. The resu...
Using ANSYS for three-dimensional electrical-thermal models for radio-frequency catheter ablation
Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. 'Magnificent Milestones and Emerging Opportunities in Medical Engineering' (Cat. No.97CH36136), 1997
A three-dimensional finite element model was developed using ANSYS, a commercial finite element analysis software. The effect of temperature-dependent electrical and thermal conductivities to the FE model which incorporated cardiac muscle, blood, electrode and catheter body, was investigated in this study. Computer simulations were performed to calculate the temperature distribution during RF ablation. We compared the results of the two cases. For the first case, we used constant properties of the cardiac muscle. The other case had varying temperature dependent properties. The maximum temperatures found in the cardiac tissue for both cases are significantly different. The lesion depth and volume were larger for the second case. However, the locations of the maximum temperature of both cases were the same. A careful examination of the heattransfer system during RF ablation is needed. I.
2018
The outcome of radio frequency thermal ablation (RFTA) is significantly affected by the tissue electrical conductivity; thus, understanding the changes of this property during heating is fundamental to suitably model the medical procedure. In this work a reasonable procedure is proposed for selecting the appropriate experimental data of the temperature dependence of electrical conductivity for the simulation taking into account the heating rate at which the data was acquired and the power that will be delivered to the electrodes in the RFTA situation of interest, based on the computing of the time average of the heating rate in a representative point of the ablation zone. The numerical results confirmed that the use of lower frequencies (20 kHz) than currently used during RFTA (450 kHz) may result in preferential heating of the tumor and consequently in less damage on healthy tissue. Also, the effect on the computed thermal lesion size of three different models of the temperature de...
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing, 1999
A variety of basic factors such as electrode tip pressure, flow around the electrode and electrode orientation influence lesion size during radiofrequency ablation, but importantly is dependent on the chosen mode of ablation. However, only little information is available for the frequently used temperature-controlled mode. The purpose of the present experimental study was to evaluate the impact during temperature-controlled radiofrequency ablation of three basic factors regarding electrode-tissue contact and convective cooling on lesion size. In vitro strips of porcine left ventricular myocardium were ablated in a tissue bath. Temperature-controlled ablation at 80 degrees C for 60 s was performed using a 7F 4 mm tip electrode in either perpendicular or parallel contact with the endocardium at a pressure of 10 or 20 g. Increased flow around the electrode was induced by circulating the saline in the tissue bath at a flow-velocity of 0.1 m/s. Lesion volume was determined by cutting les...
Toward fluid radiofrequency ablation of cardiac tissue: modeling, analysis and simulations
arXiv (Cornell University), 2023
This paper deals with the mathematical analysis and numerical simulation of a new nonlinear ablation system modeling radiofrequency ablation phenomena in cardiac tissue, which incorporates the effects of blood flow on the heat generated when ablation by radiofrequency. The model also considers the effects of viscous energy dissipation. It consists of a coupled thermistor problem and the incompressible Navier-Stokes equations that describe the evolution of temperature, velocity and potential in cardiac tissue. In addition to Faedo-Galerkin method, we use Schauder's fixed-point theory to prove the existence of the weak solutions in two-and three-dimensional space. Moreover, we prove the uniqueness of the solution under some additional conditions on the data and the solution. Finally, we discuss some numerical results for the validation of the proposed model using the finite element method. 1.2. Governing equations In this section, we describe the coupled system modeling the dynamic of RFA treatment in the presence of a fluid. Let us first describe the geometric configurations. Let Ω ⊂ ℝ , = 2, 3 is a bounded domain with a 1,1 boundary
Pacing and clinical electrophysiology : PACE, 1989
The characteristics of radiofrequency catheter ablation induced injury in the heart are not well characterized. Since the mechanism of injury by radiofrequency energy is thermal, this study was performed to determine the temperature gradient in myocardial tissue during radiofrequency (RF) catheter ablation, and to validate a thermodynamic model derived to describe these observations. Lesions were created by RF heating in an experimental model of isolated perfused and superfused canine right ventricular (RV) free wall. RF power output was adjusted to maintain electrode tip temperature at 80 degrees C for 120 seconds in 151 serial lesions and radial temperature gradients were measured. With increasing distance from the electrode, the temperature of the myocardium decreased in a hyperbolic form that was closely predicted by a derived thermodynamic model (P = 0.0001, r = 0.98). This gradient and resultant lesion sizes were unaffected by the rate of coronary perfusion. The utility of tip...