Radiofrequency Ablation with an Internally Cooled Monopolar Directional Electrode: Ex Vivo and in Vivo Experimental Studies in the Liver

Abstract The application of radiofrequency ablation (RFA) has been widely explored in treating various types of cardiac arrhythmias. Computational modelling provides a safe and viable alternative to ex vivo and in vivo experimental studies for quantifying the effects of different variables efficiently and reliably, apart from providing a priori estimates of the ablation volume attained during cardiac ablation procedures. In this contribution, we report a fully coupled thermo-electro-mechanical model for a more accurate prediction of the treatment outcomes during the radiofrequency cardiac ablation. A numerical model comprising of cardiac tissue and the cardiac chamber has been developed in which an electrode has been inserted perpendicular to the cardiac tissue to simulate actual clinical procedures. Temperature-dependent heat capacity, electrical and thermal conductivities, and blood perfusion rate have been considered to model more realistic scenarios. The effects of blood flow and contact force of the electrode tip on the efficacy of a fully coupled model of RFA have been systematically investigated. The numerical study predicts that the efficacy of RFA is significantly dependent on the thermo-electro-mechanical parameters of the cardiac tissue.

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Perivascular vital cells in the ablation center after multibipolar radiofrequency ablation in an in vivo porcine model

Scientific Reports ◽

10.1038/s41598-021-93406-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

F. G. M. Poch ◽

C. A. Neizert ◽

B. Geyer ◽

O. Gemeinhardt ◽

S. M. Niehues ◽

...

Keyword(s):

Radiofrequency Ablation ◽

Early Stage ◽

Pringle Maneuver ◽

Vessel Diameter ◽

Inflow Occlusion ◽

White Zone ◽

Cell Vitality ◽

Internally Cooled ◽

Hepatic Vessels

AbstractMultibipolar radiofrequency ablation (RFA) is an advanced ablation technique for early stage hepatocellular carcinoma and liver metastases. Vessel cooling in multibipolar RFA has not been systematically investigated. The objective of this study was to evaluate the presence of perivascular vital cells within the ablation zone after multibipolar RFA. Multibipolar RFA were performed in domestic pigs in vivo. Three internally cooled bipolar RFA applicators were used simultaneously. Three experimental settings were planned: (1) inter-applicator-distance: 15 mm; (2) inter-applicator-distance: 20 mm; (3) inter-applicator-distance: 20 mm with hepatic inflow occlusion (Pringle maneuver). A vitality staining was used to analyze liver cell vitality around all vessels in the ablation center with a diameter > 0.5 mm histologically. 771 vessels were identified. No vital tissue was seen around 423 out of 429 vessels (98.6%) situated within the central white zone. Vital cells could be observed around major hepatic vessels situated adjacent to the ablation center. Vessel diameter (> 3.0 mm; p < 0.05) and low vessel-to-ablation-center distance (< 0.2 mm; p < 0.05) were identified as risk factors for incomplete ablation adjacent to hepatic vessels. The vast majority of vessels, which were localized in the clinically relevant white zone, showed no vital perivascular cells, regardless of vessel diameter and vessel type. However, there was a risk of incomplete ablation around major hepatic vessels situated directly within the ablation center. A Pringle maneuver could avoid incomplete ablations.

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Computational Investigation of Transmural Differences in Left Ventricular Contractility

Journal of Biomechanical Engineering ◽

10.1115/1.4034558 ◽

2016 ◽

Vol 138 (11) ◽

Cited By ~ 6

Author(s):

Hua Wang ◽

Xiaoyan Zhang ◽

Shauna M. Dorsey ◽

Jeremy R. McGarvey ◽

Kenneth S. Campbell ◽

...

Keyword(s):

Myocardial Contractility ◽

Ex Vivo ◽

Experimental Studies ◽

Contractile Force ◽

Left Ventricular ◽

Lv Function ◽

Fe Model ◽

Myocardial Layers ◽

Best Fit

Myocardial contractility of the left ventricle (LV) plays an essential role in maintaining normal pump function. A recent ex vivo experimental study showed that cardiomyocyte force generation varies across the three myocardial layers of the LV wall. However, the in vivo distribution of myocardial contractile force is still unclear. The current study was designed to investigate the in vivo transmural distribution of myocardial contractility using a noninvasive computational approach. For this purpose, four cases with different transmural distributions of maximum isometric tension (Tmax) and/or reference sarcomere length (lR) were tested with animal-specific finite element (FE) models, in combination with magnetic resonance imaging (MRI), pressure catheterization, and numerical optimization. Results of the current study showed that the best fit with in vivo MRI-derived deformation was obtained when Tmax assumed different values in the subendocardium, midmyocardium, and subepicardium with transmurally varying lR. These results are consistent with recent ex vivo experimental studies, which showed that the midmyocardium produces more contractile force than the other transmural layers. The systolic strain calculated from the best-fit FE model was in good agreement with MRI data. Therefore, the proposed noninvasive approach has the capability to predict the transmural distribution of myocardial contractility. Moreover, FE models with a nonuniform distribution of myocardial contractility could provide a better representation of LV function and be used to investigate the effects of transmural changes due to heart disease.

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A minimally invasive catheter-based ultrasound technology for therapeutic interventions in brain: initial preclinical studies

Neurosurgical FOCUS ◽

10.3171/2017.11.focus17631 ◽

2018 ◽

Vol 44 (2) ◽

pp. E13 ◽

Cited By ~ 4

Author(s):

Goutam Ghoshal ◽

Lucy Gee ◽

Tamas Heffter ◽

Emery Williams ◽

Corinne Bromfield ◽

...

Keyword(s):

Parkinson’S Disease ◽

Parkinson's Disease ◽

Minimally Invasive ◽

Focused Ultrasound ◽

Ex Vivo ◽

Experimental Studies ◽

Rodent Model ◽

Therapeutic Interventions ◽

Porcine Liver

OBJECTIVEMinimally invasive procedures may allow surgeons to avoid conventional open surgical procedures for certain neurological disorders. This paper describes the iterative process for development of a catheter-based ultrasound thermal therapy applicator.METHODSUsing an ultrasound applicator with an array of longitudinally stacked and angularly sectored tubular transducers within a catheter, the authors conducted experimental studies in porcine liver, in vivo and ex vivo, in order to characterize the device performance and lesion patterns. In addition, they applied the technique in a rodent model of Parkinson’s disease to investigate the feasibility of its application in brain.RESULTSThermal lesions with multiple shapes and sizes were readily achieved in porcine liver. The feasibility of catheter-based focused ultrasound in the treatment of brain conditions was demonstrated in a rodent model of Parkinson’s disease.CONCLUSIONSThe authors show proof of principle of a catheter-based ultrasound system that can create lesions with concurrent thermode-based measurements.

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