Korean J Radiol.  2014 Apr;15(2):235-244. 10.3348/kjr.2014.15.2.235.

Monopolar Radiofrequency Ablation Using a Dual-Switching System and a Separable Clustered Electrode: Evaluation of the In Vivo Efficiency

• Yoon JH
• Lee JM
• Hwang EJ
• Hwang IP
• Baek J
• Han JK
• Choi BI

• KMID: 1705578
• DOI: http://doi.org/10.3348/kjr.2014.15.2.235

Abstract

OBJECTIVE
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.
MATERIALS AND METHODS
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.
RESULTS
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 cm3 vs. 20.8 +/- 10.7 cm3; p < 0.001). Both groups showed similar circularity of the ablation zones (p = 0.29).
CONCLUSION
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.

Keyword

Liver; Interventional procedures; Thermal ablation; Radiofrequency ablation; Experimental study

MeSH Terms

Animals
Catheter Ablation/*instrumentation/*methods
*Electrodes
Feasibility Studies
Liver/*surgery
Male
Sus scrofa
Time Factors

Figure

• 

  Fig. 1 Prototype three-channel, dual-generator radiofrequency ablation unit (A) and single separable clustered (Octopus®) electrode (B).

• 

  Fig. 2 Comparison of ablation zones created by dual-switching monopolar radiofrequency ablation (DSM-RFA) at inter-electrode distances (IEDs) of 2.0 cm (A), 2.5 cm (B), 3.0 cm (C), and 3.5 cm (D). Note that ablation zones created in DSM-RFA at 2.0 cm and 2.5 cm IEDs showed united, round/oval-shaped lesions (A, B), although ablation zones at 3.0 cm and 3.5 cm IEDs were separated (C, D).

• 

  Fig. 3 Diagrams of radiofrequency (RF) energy delivery patterns during single-switching monopolar (SSM)-radiofrequency ablation (RFA) (A) and dual-switching monopolar (DSM)-RFA (B). A. SSM-RFA: RF energy (maximum 200 W) was applied to one of three electrodes and was switched among three electrode tips of SC electrode, depending on tissue impedance changes, for total of 12 minutes. B. DSM-RFA: synchronous parallel RF energy (maximum 330 W; 165 + 165 W) was applied to pair of three electrodes, and RF energy was delivered in alternating fashion to possible three pairs of electrodes of SC electrode, similar to SSM-RFA.

• 

  Fig. 4 Photographs of radiofrequency ablation (RFA)-induced ablation zones created by single-switching monopolar (SSM)-RFA and dual-switching monopolar (DSM)-RFA at 2-cm or 2.5-cm inter-electrode distances (IEDs). A. Transverse cut section of specimen created in DSM-RFA with 2-cm IED. Ablation zone was approximately 6.5 × 5.0 cm2. B. Transverse cut section of specimen created with DSM-RFA and 2.5-cm IED. Area of ablation zone was 4.5 × 5.0 cm2. Note that ablation zone is triangular shaped. C. Transverse cut section of specimen created in SSM-RFA with 2.0-cm IED. Maximum and minimum diameters of ablation zone were 5.8 cm and 5.3 cm, respectively. D. Transverse cut section of specimen created in SSM-RFA with 2.5-cm IED. Note that ablation zone was separated.

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