A Three-Dimensional Finite Element Model of Radiofrequency Ablation with Blood Flow and its Experimental Validation

Abstract

A novel three-dimensional finite element model for the study of radiofrequency ablation is presented. The model was used to perform an analysis of the temperature distribution in a tissue block heated by RF energy and cooled by blood (fluid) flow. This work extends earlier models by including true flow in place of a convective boundary condition to simulate realistic experimental conditions and to improve the prediction of blood temperatures. The effect of fluid flow on the temperature distribution, the lesion dimensions, and the ablation efficiency was studied. Three flow velocities were simulated: (i) 30, (ii) 55, and (iii) 85 mm/s. The modeling results were validated qualitatively and quantitatively with in vitro data. The correlation coefficients between the modeling and the experimental temperature measurements were 0.98, 0.97, and 0.95 for flows (i)-(iii), respectively. The slopes were 0.89, 0.95, and 1.06, and the mean root mean square differences between modeling and experimental temperature measurements were 17.3% +/- 11.6%, 15.8% +/- 13.4%, and 18.8% +/- 14.9% for flows (i)-(iii), respectively. A comparison of temperature distribution obtained with a convective boundary versus inclusion of fluid motion showed that the convective boundary resulted in a similar tissue temperature distribution, but overestimated fluid temperatures and lacked the flow asymmetry seen in the true flow model.

Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

“…In 1999, Jain and Wolf [10] suggested that computer simulations in which the temperature-dependent electrical conductivity is only considered for the cardiac tissue but not for the blood could somehow compensate the positive feedback by which temperature in the blood increases unrealistically. Subsequently, Jain and Wolf proposed the first RFCA model to take blood motion into account by estimating the fluid velocity field [24]. Their results suggested that including the fluid motion problem provides a realistic distribution of blood temperature and moreover is able to mimic the asymmetric temperature distribution in tissue and blood, where higher temperatures are observed on the outflow than the inflow side [24].…”

Considerations for Thermal Injury Analysis for RF Ablation Devices

“…Several studies have been conducted to describe lesion growth for radiofrequency ablation devices [2,[9][10][11][12]21,24,[29][30][34][35]. In the majority of these cases, markers such as temperature isotherms and thermal dosing are used as the primary measure for lesion size.…”

“…The temperature thresholds that have been used to predict lesion size and define thermal injury are well documented in the literature . The most common temperatures used are 43°C [22,23], 48°C [24,25], 50°C [9,13,14], and 59°C [12]. While some of this variation is attributable to differences in tissue *Address correspondence to this author at the U.S. Food and Drug Administration, White Oak, MD 20993, USA; E-mail: Isaac.Chang@fda.hhs.gov type (i.e.…”

Radiofrequency cardiac ablation with catheters placed on opposing sides of the ventricular wall: Computer modelling comparing bipolar and unipolar modes

“…In any case, it is generally accepted that this aspect would not affect either the temperature distribution in the tissue or the lesions created in the ventricular wall, but would provide a more realistic temperature distribution in the blood [31]. h CL = h CR and h EL = h ER are the thermal transfer coefficients at the endocardium-blood and the electrode-blood interfaces, respectively.…”