Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

Alba-Martínez, Jose; Trujillo, Macarena; Blasco-Gimenez, Ramon; Berjano, Enrique

doi:10.3109/02656736.2011.586665

Cited by 11 publications

(7 citation statements)

References 21 publications

(37 reference statements)

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“…The electrode was assumed to be inserted into the tissue to a depth (D E ) of 1.25 mm [14]. The model included a temperature sensor (thermistor 0.75 × 0.3 mm) embedded in the tip of the electrode, which was used for the temperature control simulation [5,14,20]. The dispersive electrode was modeled as an electrical boundary condition at a distance from the active electrode (bottom surface).…”

Section: Comparative Analysis Of Different Methods Ofmentioning

confidence: 99%

“…2b and 2c show the thermal and velocity boundary conditions. The effect of blood circulating inside the cardiac chamber was modeled by four methods which have been used in previous studies [3,5,[9][10][11][13][14][15]17,20,24]. Each case was assessed under conditions of high and low blood flow.…”

Section: Properties Of the Model Elementsmentioning

confidence: 99%

“…From that time on all models have considered in one form or another the thermal effect of circulating blood. Some models do not consider blood as part of the model domain, and consequently the blood-tissue and blood-electrode interfaces were really model boundaries [3][4][5][6][7][8] on which an electrical boundary condition of zero current density was set. Other models consider blood as part of the domain [9][10][11][12][13][14][15][16][17][18][19][20][21], thus allowing RF current to flow through the blood.…”

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confidence: 99%

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

González-Suárez

Berjano

2016

IEEE Trans. Biomed. Eng.

146

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Abstract-Goal: Our aim was to compare the different methods of modeling the effect of circulating blood flow on the thermal lesion dimensions created by radiofrequency cardiac ablation and on the maximum blood temperature. Methods: Computational models were built to study the temperature distributions and lesion dimensions created by a non-irrigated electrode by two radiofrequency energy delivery protocols (constant voltage and constant temperature) under high and low blood flow conditions. Four methods of modeling the effect of circulating blood flow on lesion dimensions and temperature distribution were compared. Three of them considered convective coefficients at the electrode-blood and tissue-blood interfaces to model blood flow: 1) without including blood as a part of the domain; 2) constant electrical conductivity of blood; and 3) temperature-dependent electrical conductivity of blood (+2%/ºC). Method 4) included blood motion and was considered to be a reference method for comparison purposes. Results: Only Method 4 provided a realistic blood temperature distribution. The other three methods predicted lesion depth values similar to those of the reference method (differences smaller than 1 mm), regardless of ablation mode and blood flow conditions. Conclusion: Considering the aspects of lesion size and maximum temperature reached in blood and tissue, Method 2 seems to be the most suitable alternative to Method 4 in order to reduce the computational complexity. Significance: Our findings could have an important implication in future studies of RF cardiac ablation, in particular, in choosing the most suitable method to model the thermal effect of circulating blood.

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Section: Comparative Analysis Of Different Methods Ofmentioning

confidence: 99%

Section: Properties Of the Model Elementsmentioning

confidence: 99%

mentioning

confidence: 99%

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

González-Suárez

Berjano

2016

IEEE Trans. Biomed. Eng.

146

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“…These algorithms alter the delivery of RF energy into the tissue based on pre‐determined threshold, such as tissue impedance and temperature. Changes to the RF energy delivery can be executed either in a pulse manner by repeatedly switching on and off the RF generator 38‐40 or continuously via some feedback controller such as the proportional‐integral‐derivative controller 41‐44 . More recently, a broad control system that takes into consideration the area of the tumour tissue and the tumour temperature was proposed 45 .…”

Section: Methodsmentioning

confidence: 99%

Thermal and thermal damage responses during switching bipolar radiofrequency ablation employing bipolar needles: A computational study on the effects of different electrode configuration, input voltage and ablation duration

Cheong

Ooi

2020

Numer Methods Biomed Eng

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Recent studies have demonstrated the effectiveness of switching bipolar radiofrequency ablation (bRFA) in treating liver cancer. Nevertheless, the clinical use of the treatment remains less common than conventional monopolar RFA – likely due to the lack of understanding of how the tissues respond thermally to the switching effect. The problem is exacerbated by the numerous possible switching combinations when bRFA is performed using bipolar needles, thus making theoretical deduction and experimental studies difficult. This article addresses this issue via computational modelling by examining if significant variation in the treatment outcome exists amongst six different electrode configurations defined by the X‐, C‐, U‐, N‐, Z‐ and O‐models. Results indicated that the tissue thermal and thermal damage responses varied depending on the electrode configuration and the operating conditions (input voltage and ablation duration). For a spherical tumour, 30 mm in diameter, complete ablation could not be attained in all configurations with 70 V input voltage and 5 minutes ablation duration. Increasing the input voltage to 90 V enlarged the coagulation zone in the X‐model only. With the other configurations, extending the ablation duration to 10 minutes was found to be the better at enlarging the coagulation zone.

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“…Therefore, we used a PI controller with a target temperature of 55ºC. The values of the Kp and Ki of the PI controller were 4.78 and 3.39, respectively [13]. The change in cardiac tissue electrical conductivity was taken as +1.5%/ºC [10] and in thermal conductivity as +0.001195K -1 [14].…”

Section: Methodsmentioning

confidence: 99%

Mathematical Models Based on Transfer Functions to Estimate Tissue Temperature During RF Cardiac Ablation in Real Time

Alba-Martínez

Trujillo²,

Blasco-Gimenez³

et al. 2012

TOBEJ

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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 using a 7Fr and 4 mm electrode. The results showed that the relationships can be expressed as first-order transfer functions. Changes in electrical conductivity only affected the static gain of the system, while specific heat variations produced a change in the dynamic system response. In contrast, variations in thermal conductivity modified both the static gain and the dynamic system response. Finally, to assess the performance of the transfer functions obtained, we conducted a new set of computer simulations using a controlled temperature protocol and considering the temperature dependence of the thermal and electrical conductivities, i.e. conditions closer to those found in clinical use. The results showed that the difference between the values estimated from transfer functions and the temperatures obtained from finite element models was less than 4ºC, which suggests that the proposed method could be used to estimate tissue temperature in real time.

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Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models

Cited by 11 publications

References 21 publications

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

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

Thermal and thermal damage responses during switching bipolar radiofrequency ablation employing bipolar needles: A computational study on the effects of different electrode configuration, input voltage and ablation duration

Mathematical Models Based on Transfer Functions to Estimate Tissue Temperature During RF Cardiac Ablation in Real Time

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