Korean J Radiol.  2013 Jun;14(3):403-411. 10.3348/kjr.2013.14.3.403.

Dual Switching Monopolar Radiofrequency Ablation Using a Separable Clustered Electrode: Comparison with Consecutive and Switching Monopolar Modes in Ex Vivo Bovine Livers

• Yoon JH
• Lee JM
• Han JK
• Choi BI

• KMID: 1705451
• DOI: http://doi.org/10.3348/kjr.2013.14.3.403

Abstract

OBJECTIVE
To compare the in-vitro efficiency of dual-switching monopolar (DSM) radiofrequency ablation (RFA) using a separable clustered electrode (Octopus(R) electrodes) with consecutive monopolar (CM) and switching monopolar (SM) RFA techniques to create an ablative zone in the explanted bovine liver.
MATERIALS AND METHODS
For DSM-RFA, we used a prototype, three-channel, dual generator RFA Unit and Octopus(R) electrodes with three, 17 gauge internally cooled electrodes. The RFA Unit allowed simultaneous radiofrequency (RF) energy delivery to two electrodes of the Octopus(R) electrodes as well as automatic switching among the three electrode pairs according to the impedance changes. RF energy was sequentially applied to one of the three electrodes for 24 minutes (group A; CM mode, n = 10) or alternatively applied for 12 minutes (group B; SM mode, n = 10) or concurrently applied to a pair of electrodes for 12 minutes (group C; DSM mode, n = 10) in explanted bovine livers. Changes in the impedance and current during RFA as well as the dimensions of the thermal ablative zones were compared among the three groups.
RESULTS
The mean, delivered RF energy amounts in groups A, B, and C were 63.15 +/- 8.6 kJ, 72.13 +/- 5.4 kJ, and 106.08 +/- 13.4 kJ, respectively (p < 0.001). The DSM mode created a significantly larger ablation volume than did the other modes, i.e., 68.1 +/- 10.2 cm3 (group A), 92.0 +/- 19.9 cm3 (group B), and 115.1 +/- 14.0 cm3 (group C) (p < 0.001). The circularity in groups A, B, and C were 0.84 +/- 0.06, 0.87 +/- 0.04 and 0.90 +/- 0.03, respectively (p = 0.03).
CONCLUSION
DSM-RFA using Octopus(R) electrodes can help create large ablative zones within a relatively short time.

Keyword

Liver, interventional procedures; Radiofrequency ablation; Experimental study

MeSH Terms

Analysis of Variance
Animals
Catheter Ablation/*instrumentation/methods
Cattle
Electric Impedance
Electrodes
Equipment Design
Liver/*surgery

Figure

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  Fig. 1 Photographs of single Octopus® electrode and prototype three-channel dual generator radiofrequency ablation unit.

• 

  Fig. 2 Diagram showing typical patterns of radiofrequency energy delivery during radiofrequency ablation in three groups. A. Consecutive mode: radiofrequency (RF) energy was consecutively applied to each electrode for eight minutes by changing current flow to second electrode just after ablation with first electrode (in total 24 minutes). B. Switching monopolar mode: RF energy (- maximum 200 W) was applied to one of three electrodes and was switched between three electrode tips of Octopus® electrode depending on tissue impedance changes for total of 12 minutes. C. Dual switching mode: synchronous parallel RF energy (- maximum 400 W; 200 + 200 W) was applied to pair of three electrodes; similar to switching monopolar mode, RF energy was delivered in alternating fashion to three possible pairs of electrodes of Octopus® electrode.

• 

  Fig. 3 Comparison of radiofrequency ablation (RFA)-induced coagulation created by applying radiofrequency in consecutive, switching, and dual switching modes and with 3 cm, inter-electrode distance. A. Transverse cut section of specimen created in consecutive monopolar RFA showed 4.54 × 5.03 sized ablation area. B. Transverse cut section of specimen created in switching monopolar RFA. Long-axis and short-axis diameters of ablative zone were 5.77 cm and 5.29 cm, respectively. C. Transverse cut section of specimen created in dual switching RFA. Long-axis and short-axis diameters of ablative zone were 6.78 cm and 6.55 cm, respectively.

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