Thermal modeling of lesion growth with radiofrequency ablation devices

Chang, Isaac; Nguyen, Uyen D.

doi:10.1186/1475-925x-3-27

Cited by 205 publications

(121 citation statements)

References 53 publications

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“…The geometry of the electrode and tissue was constructed in a 2-D axis symmetric model in order to capitalize in the rotational symmetry and generate the solutions in a more computationally efficient manner than the equivalent 3-D model. The liver tissue domain was selected to be 24 cm in length (z-direction) and 12 cm in width (r-direction) which represents a 3-D cylindrical domain which is twice the dimensions of the one implemented by Chang et al in order to prevent edge effects [47]. Due to rotational symmetry of the geometry, only the electrode radius (0.825 mm) was modeled as depicted in Figure 1B .…”

Section: Methodsmentioning

confidence: 99%

A Numerical Investigation of the Electric and Thermal Cell Kill Distributions in Electroporation-Based Therapies in Tissue

2014

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Electroporation-based therapies are powerful biotechnological tools for enhancing the delivery of exogeneous agents or killing tissue with pulsed electric fields (PEFs). Electrochemotherapy (ECT) and gene therapy based on gene electrotransfer (EGT) both use reversible electroporation to deliver chemotherapeutics or plasmid DNA into cells, respectively. In both ECT and EGT, the goal is to permeabilize the cell membrane while maintaining high cell viability in order to facilitate drug or gene transport into the cell cytoplasm and induce a therapeutic response. Irreversible electroporation (IRE) results in cell kill due to exposure to PEFs without drugs and is under clinical evaluation for treating otherwise unresectable tumors. These PEF therapies rely mainly on the electric field distributions and do not require changes in tissue temperature for their effectiveness. However, in immediate vicinity of the electrodes the treatment may results in cell kill due to thermal damage because of the inhomogeneous electric field distribution and high current density during the electroporation-based therapies. Therefore, the main objective of this numerical study is to evaluate the influence of pulse number and electrical conductivity in the predicted cell kill zone due to irreversible electroporation and thermal damage. Specifically, we simulated a typical IRE protocol that employs ninety 100-µs PEFs. Our results confirm that it is possible to achieve predominant cell kill due to electroporation if the PEF parameters are chosen carefully. However, if either the pulse number and/or the tissue conductivity are too high, there is also potential to achieve cell kill due to thermal damage in the immediate vicinity of the electrodes. Therefore, it is critical for physicians to be mindful of placement of electrodes with respect to critical tissue structures and treatment parameters in order to maintain the non-thermal benefits of electroporation and prevent unnecessary damage to surrounding healthy tissue, critical vascular structures, and/or adjacent organs.

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Section: Methodsmentioning

confidence: 99%

A Numerical Investigation of the Electric and Thermal Cell Kill Distributions in Electroporation-Based Therapies in Tissue

2014

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“…This may be due to greater gas generation in the unperfused liver. Blood perfusion introduces a “heat-sink” effect that mitigates heat and mass transfer so greater vaporization would be expected in tissue lacking blood flow (Goldberg et al 1998, Chang and Nguyen 2004). However, this hypothesis would need additional controlled experimentation for confirmation.…”

Section: Discussionmentioning

confidence: 99%

Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

Brace

2016

Phys. Med. Biol.

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Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR = 1.57±0.73, boundary gradient = 0.7±0.4 HU/mm), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR = 2.04±0.84, boundary gradient = 6.3±1.1 HU/mm) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient = 3.9±1.1 HU/mm). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility was highest when contrast is delivered intra-procedurally. Therefore, CECT may be feasible for real-time thermal ablation monitoring.

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“…The cumulative tissue damage of EM hyperthermia-induced ablation zone can be calculated by using the following Arrhenius equation [22]: XðtÞ ¼ ln…”

Section: Thermal Lesion Quantificationmentioning

confidence: 99%

“…where X(t) is the cumulative tissue damage as a function of time and n cell (t) denotes the concentration of living cells; R a and A denote the universal gas constant (8.3145 J/mol K) and the frequency factor (7.39 Â 1039 s À1 ), respectively [22,23]; and DE is the activation energy for the irreversible damage reaction (2.5774 Â 105 J/mol) [22,23].…”

Section: Thermal Lesion Quantificationmentioning

confidence: 99%

Thermal Electrical Property Effects of Bone Structure on the Magnetic-Nanoparticle Enhanced Hyperthermia Targeting Tumor Underneath the Ribs

Jin

Jing

2015

Journal of Heat Transfer

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Bone has very different thermal and electrical properties with the surrounding tissues. Misjustification of the heating dosage during an electromagnetic (EM) hyperthermia may lead to the failure of the treatment. Here aiming to disclose such clinically important issue, the present study presented a theoretical evaluation on the heating effects of magnetic-nanoparticles (MNPs) enhanced hyperthermia on the liver tumor underneath the ribs with bone features particularly addressed. The results revealed the following factors: (1) The existence of bone structure, i.e., ribs has an inevitable effect on the distribution of EM field; specifically, due to its lower dielectric property, the bone structure served as a barrier to attenuate the transport of EM energy and conversion of heat into the tissues, especially the tumor in the deep body.(2) Applying higher dosage or larger size MNPs would significantly enhance the temperature elevation at the target tumor tissues and thereby guarantee the performance of the hyperthermia. (3) Further parametric studies indicated that a higher frequency EM field would result in a worse heating effect; while stronger EM field will evidently enhance the heating effects of the hyperthermia process. This study promoted the better understanding of the EM heating on the bone structured tissues, and the findings are expected to provide valuable reference for planning an accurate surgery in future clinical liver tumor EM ablation.

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Thermal modeling of lesion growth with radiofrequency ablation devices

Cited by 205 publications

References 53 publications

A Numerical Investigation of the Electric and Thermal Cell Kill Distributions in Electroporation-Based Therapies in Tissue

A Numerical Investigation of the Electric and Thermal Cell Kill Distributions in Electroporation-Based Therapies in Tissue

Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

Thermal Electrical Property Effects of Bone Structure on the Magnetic-Nanoparticle Enhanced Hyperthermia Targeting Tumor Underneath the Ribs

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