Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity

Chang, Isaac

doi:10.1186/1475-925x-2-12

Cited by 111 publications

(49 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Any form of electrical stimulation produces passive heating and the extent of induced temperature increases are specific to both the stimulation and local tissue properties, with various stimulation and environmental parameters affecting the degree to which heating occurs 19,23,27 . Key stimulation parameters are the stimulation waveform (based on stimulator programming) and electrode montage (based on lead placement), which together with tissue anatomy and electrical conductivity determine joule heat deposition.…”

Section: Introductionmentioning

confidence: 99%

Temperature increases by kilohertz frequency spinal cord stimulation

et al. 2019

View full text Add to dashboard Cite

Introduction: Kilohertz frequency spinal cord stimulation (kHz-SCS) deposits significantly more power in tissue compared to SCS at conventional frequencies, reflecting increased duty cycle (pulse compression). We hypothesize kHz-SCS increases local tissue temperature by joule heat, which may influence the clinical outcomes. Methods: To establish the role of tissue heating in KHZ-SCS, a decisive first step is to characterize the range of temperature changes expected during conventional and KHZ-SCS protocols. Fiber optic probes quantified temperature increases around an experimental SCS lead in a bath phantom. These data were used to verify a SCS lead heat-transfer model based on joule heat. Temperature increases were then predicted in a seven-compartment (soft tissue, vertebral bone, fat, intervertebral disc, meninges, spinal cord with nerve roots) geometric human spinal cord model under varied parameterization. Results: The experimentally constrained bio-heat model shows SCS waveform power (waveform RMS) determines tissue heating at the spinal cord and surrounding tissues. For example, we predict temperature increased at dorsal spinal cord of 0.18–1.72 °C during 3.5 mA peak 10 KHz stimulation with a 40–10–40 μs biphasic pulse pattern, 0.09–0.22 °C during 3.5 mA 1 KHz 100–100–100 μs stimulation, and less than 0.05 °C during 3.5 mA 50 Hz 200–100–200 μs stimulation. Notably, peak heating of the spinal cord and other tissues increases superlinearly with stimulation power and so are especially sensitive to incremental changes in SCS pulse amplitude or frequency (with associated pulse compression). Further supporting distinct SCS intervention strategies based on heating; the spatial profile of temperature changes is more uniform compared to electric fields, which suggests less sensitivity to lead position. Conclusions: Tissue heating may impact short and long-term outcomes of KHZ-SCS, and even as an adjunct mechanism, suggests distinct strategies for lead position and programming optimization.

show abstract

Section: Introductionmentioning

confidence: 99%

Temperature increases by kilohertz frequency spinal cord stimulation

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Joule heating arises when energy dissipated by an electric current flowing through a conductor is converted into thermal energy. The resulting bioheat equation (1) governs heating during electrical stimulation [29-33].

ρ C_{p} \frac{\partial_{T}}{\partial_{t}} = \nabla_{(k^{\nabla} T)} - ρ_{b} ω_{b} C_{b} (T - T_{b}) + Q_{m} + σ {∣ \nabla_{v} ∣}^{2}

Where ρ b is the blood density (kg/m3), C b is the heat capacity of the blood (J/kg °C), k is the thermal conductivity of the brain tissue (W/m °C), T is the temperature (°C), ω b is the blood perfusion (ml/s/ml), is the brain tissue density, C p is the specific heat of the brain tissue (J/kg °C), T b is the body core temperature (°C), Q m is the metabolic heat source term (W/m 3 ).…”

Section: Model Methods and Analysismentioning

confidence: 99%

Temperature control at DBS electrodes using a heat sink: experimentally validated FEM model of DBS lead architecture

et al. 2012

View full text Add to dashboard Cite

There is a growing interest in the use of Deep Brain Stimulation for the treatment of medically refractory movement disorders and other neurological and psychiatric conditions. The extent of temperature increases around DBS electrodes during normal operation (joule heating and increased metabolic activity) or coupling with an external source (e.g. MRI) remains poorly understood and methods to mitigate temperature increases are being actively investigated. We developed a heat transfer finite element method simulation of DBS incorporating the realistic architecture of Medtronic 3389 leads. The temperature changes were analyzed considering different electrode configurations, stimulation protocols, and tissue properties. The heat-transfer model results were then validated using micro-thermocouple measurements during DBS lead stimulation in a saline bath. FEM results indicate that lead design (materials and geometry) may have a central role in controlling temperature rise by conducting heat. We show how modifying lead design can effectively control temperature increases. The robustness of this heat-sink approach over complimentary heat-mitigation technologies follows from several features: 1) it is insensitive to the mechanisms of heating (e.g. nature of magnetic coupling); 2) does not interfere with device efficacy; and 3) can be practically implemented in a broad range of implanted devices without modifying the normal device operations or the implant procedure.

show abstract

“…RFA models have been applied in thyroid tissue based on reconstructed models from magnetic resonance imaging and also in liver-tissue using a hyperbolic bioheat equation and a new-voltage calibration method [18,19]. Various ablation models have been used to study the effects of tissue properties such as electrical conductivity and blood perfusion rate [20][21][22]. Others models focus on specific commercially available electrodes [23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

“…Others models focus on specific commercially available electrodes [23][24][25][26]. Chang [20] focused on the effects of the blood perfusion rate and temperature-dependent electrical conductivity. Later, Chang and Nguyen [23] studied how isotherms can be used to predict the ablation zone.…”

Section: Introductionmentioning

confidence: 99%

Optimization of an Endoscopic Radiofrequency Ablation Electrode

Hanks

Frecker

Moyer

2018

Journal of Medical Devices

View full text Add to dashboard Cite

Radiofrequency ablation (RFA) is an increasingly used, minimally invasive, cancer treatment modality for patients who are unwilling or unable to undergo a major resective surgery. There is a need for RFA electrodes that generate thermal ablation zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone produced by an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of a specified diameter. This optimization procedure is then applied to EUS-RFA ablation of pancreatic tissue. For a target 2.5 cm spherical tumor, the optimal design parameters of the compliant electrode design are found for two cases. Cases 1 and 2 optimal solutions filled 70.9% and 87.0% of the target volume as compared to only 25.1% for a standard straight electrode. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes for a specific target shape.

show abstract

Finite Element Analysis of Hepatic Radiofrequency Ablation Probes using Temperature-Dependent Electrical Conductivity

Cited by 111 publications

References 23 publications

Temperature increases by kilohertz frequency spinal cord stimulation

Temperature increases by kilohertz frequency spinal cord stimulation

Temperature control at DBS electrodes using a heat sink: experimentally validated FEM model of DBS lead architecture

Optimization of an Endoscopic Radiofrequency Ablation Electrode

Contact Info

Product

Resources

About