Multiple-Electrode Radiofrequency Ablation Creates Confluent Areas of Necrosis: In Vivo Porcine Liver Results1

Department of Radiology, University of Wisconsin, Box 3252, Clinical Science Center-E3, 600 Highland Ave, Madison, WI 53792, USA.
Radiology (Impact Factor: 6.87). 10/2006; 241(1):116-24. DOI: 10.1148/radiol.2411051271
Source: PubMed


To prospectively evaluate, in vivo in pigs, an impedance-based multiple-electrode radiofrequency (RF) ablation system for creation of confluent areas of hepatic coagulation.
The study was preapproved by the institutional research animal care and use committee. A prototype multiple-electrode RF system that enables switching between three electrically independent electrodes at impedance spikes was created. Forty-two coagulation zones (18 with single, 12 with cluster, and 12 with multiple [three single electrodes spaced 2 cm apart] electrodes) were created at laparotomy in 15 female pigs. Half the ablations were performed for 12 minutes, and half were performed for 16 minutes. The coagulation zones were excised and sliced into approximately 3-mm sections for measurement. Analysis of variance and two-sample t tests (with Bonferroni correction, alpha = .0033) were used to assess for differences between groups.
At 12 minutes, the mean multiple-electrode coagulation was significantly larger than the mean single-electrode coagulation (minimum diameter, 2.8 vs 1.6 cm; maximum diameter, 4.2 vs 2.0 cm; volume, 22.1 vs 6.7 cm(3); P < .0033 for all comparisons). The mean maximum diameter achieved at 12 minutes with multiple electrodes was significantly larger than that achieved with the cluster electrode (4.2 vs 2.9 cm, P = .02). At 16 minutes, the mean multiple-electrode coagulation (minimum diameter, 3.2 cm; maximum diameter, 4.2 cm; volume, 29.1 cm(3)) was significantly larger than the mean single-electrode (minimum diameter, 1.7 cm; maximum diameter, 2.2 cm; volume, 7.1 cm(3); P < .0033 for all comparisons) and cluster-electrode (minimum diameter: 2.3 cm, P = .007; maximum diameter: 3.2 cm, P = .005; volume: 13.1 cm(3), P = .001) coagulations.
Compared with the single and cluster systems used as controls, the multiple-electrode RF ablation system enabled the creation of significantly larger coagulation zones.

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    • "However, it is technically challenging to place an electrode in the remaining tumor portion during overlapping ablations under ultrasound guidance due to gas bubble formation (19, 20). To overcome this technical difficulty of overlapping ablation and to generate larger ablation zones than RFA using a single electrode, multiple-electrode RF systems such as the switching controller (Valleylab, Boulder, CO, USA), the multi-channel RF generator (STARmed Co., Ltd., Goyang, Korea), and the multipolar RF system (Celon, Teltow, Germany) have been introduced and are commercially available (21-23). Several previous studies of monopolar RFA using a multiple-electrode switching system have shown its efficiency for creating a larger ablation zone in the liver than could be created using the standard monopolar RF technique (20, 24, 25). "
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    ABSTRACT: To determine the in vivo efficiency of monopolar radiofrequency ablation (RFA) using a dual-switching (DS) system and a separable clustered (SC) electrode to create coagulation in swine liver. Thirty-three ablation zones were created in nine pigs using a DS system and an SC electrode in the switching monopolar mode. The pigs were divided into two groups for two experiments: 1) preliminary experiments (n = 3) to identify the optimal inter-electrode distances (IEDs) for dual-switching monopolar (DSM)-RFA, and 2) main experiments (n = 6) to compare the in vivo efficiency of DSM-RFA with that of a single-switching monopolar (SSM)-RFA. RF energy was alternatively applied to one of the three electrodes (SSM-RFA) or concurrently applied to a pair of electrodes (DSM-RFA) for 12 minutes in in vivo porcine livers. The delivered RFA energy and the shapes and dimensions of the coagulation areas were compared between the two groups. No pig died during RFA. The ideal IEDs for creating round or oval coagulation area using the DSM-RFA were 2.0 and 2.5 cm. DSM-RFA allowed more efficient RF energy delivery than SSM-RFA at the given time (23.0 ± 4.0 kcal vs. 16.92 ± 2.0 kcal, respectively; p = 0.0005). DSM-RFA created a significantly larger coagulation volume than SSM-RFA (40.4 ± 16.4 cm(3) vs. 20.8 ± 10.7 cm(3); p < 0.001). Both groups showed similar circularity of the ablation zones (p = 0.29). Dual-switching monopolar-radiofrequency ablation using an SC electrode is feasible and can create larger ablation zones than SSM-RFA as it allows more RF energy delivery at a given time.
    Korean journal of radiology: official journal of the Korean Radiological Society 03/2014; 15(2):235-244. DOI:10.3348/kjr.2014.15.2.235 · 1.57 Impact Factor
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    • "Therefore, there have been various attempts to expand the ablation zone during a single session of RFA.7 Several needle electrodes such as internally cooled (IC), perfused, bipolar, expandable, and clustered electrodes have been developed to expand the RFA zone. Using multiple electrodes is another strategy to expand the ablation zone.8-10 Recently another energy source such as microwave has been used for thermal ablation to treat large hepatic tumors.11-13 "
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    ABSTRACT: Various strategies to expand the ablation zone have been attempted using hepatic radiofrequency ablation (RFA). The optimal strategy, however, is unknown. We compared hepatic RFA with an internally cooled wet (ICW) electrode and vascular inflow occlusion. EIGHT DOGS WERE ASSIGNED TO ONE OF THREE GROUPS: only RFA using an internally cooled electrode (group A), RFA using an ICW electrode (group B), and RFA using an internally cooled electrode with the Pringle maneuver (group C). The ablation zone diameters were measured on the gross specimens, and the volume of the ablation zone was calculated. The ablation zone volume was greatest in group B (1.82±1.23 cm(3)), followed by group C (1.22±0.47 cm(3)), and then group A (0.48±0.33 cm(3)). The volumes for group B were significantly larger than the volumes for group A (p=0.030). There was no significant difference in the volumes between groups A and C (p=0.079) and between groups B and C (p=0.827). Both the usage of an ICW electrode and hepatic vascular occlusion effectively expanded the ablation zone. The use of an ICW electrode induced a larger ablation zone with easy handling compared with using hepatic vascular occlusion, although this difference was not statistically significant.
    Gut and liver 10/2012; 6(4):471-5. DOI:10.5009/gnl.2012.6.4.471 · 1.81 Impact Factor
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    • "It has been proven that RFA using multiple electrodes creates a larger ablation volume than conventional single-electrode RFA (16, 26-34). Several preclinical in vivo experiments have shown that switching monopolar RFA can create a larger ablation volume than consecutive overlapping RFA (30, 35, 36); however, there have been only two retrospective studies reporting the early clinical experience of switching monopolar RFA for malignant liver tumors (37, 38). In one retrospective study, as the therapeutic results of switching monopolar RFA for treating malignant liver tumors, including HCCs as well as metastases, were described without distinguishing each type of tumor, the clinical efficacy of switching monopolar RFA for HCC has not yet been determined. "
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    ABSTRACT: To prospectively evaluate the safety and short-term therapeutic efficacy of switching monopolar radiofrequency ablation (RFA) with multiple electrodes to treat medium-sized (3.1-5.0 cm), hepatocellular carcinomas (HCC). In this prospective study, 30 patients with single medium-sized HCCs (mean, 3.5 cm; range, 3.1-4.4 cm) were enrolled. The patients were treated under ultrasonographic guidance by percutaneous switching monopolar RFA with a multichannel RF generator and two or three internally cooled electrodes. Contrast-enhanced CT scans were obtained immediately after RFA, and the diameters and volume of the ablation zones were then measured. Follow-up CT scans were performed at the first month after ablation and every three months thereafter. Technical effectiveness, local progression and remote recurrence of HCCs were determined. There were no major immediate or periprocedural complications. However, there was one bile duct stricture during the follow-up period. Technical effectiveness was achieved in 29 of 30 patients (97%). The total ablation time of the procedures was 25.4 ± 8.9 minutes. The mean ablation volume was 73.8 ± 56.4 cm(3) and the minimum diameter was 4.1 ± 7.3 cm. During the follow-up period (mean, 12.5 months), local tumor progression occurred in three of 29 patients (10%) with technical effectiveness, while new HCCs were detected in six of 29 patients (21%). Switching monopolar RFA with multiple electrodes in order to achieve a sufficient ablation volume is safe and efficient. This method also showed relatively successful therapeutic effectiveness on short-term follow up for the treatment of medium-sized HCCs.
    Korean journal of radiology: official journal of the Korean Radiological Society 01/2012; 13(1):34-43. DOI:10.3348/kjr.2012.13.1.34 · 1.57 Impact Factor
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