Korean J Radiol.  2006 Jun;7(2):97-105. 10.3348/kjr.2006.7.2.97.

Radio Frequency Ablation in the Rabbit Lung Using Wet Electrodes: Comparison of Monopolar and Dual Bipolar Electrode Mode

• Jin GY
• Park SH
• Han YM
• Chung GH
• Kwak HS
• Jeon SB
• Lee YC

• KMID: 1782182
• DOI: http://doi.org/10.3348/kjr.2006.7.2.97

Abstract

OBJECTIVE
To compare the effect of radio frequency ablation (RFA) on the dimensions of radio frequency coagulation necrosis in a rabbit lung using a wet electrode in monopolar mode with that in dual electrode bipolar mode at different infusion rates (15 mm/hr versus 30 ml/hr) and saline concentrations (0.9% normal versus 5.8% hypertonic saline) . MATERIALS AND METHODS: Fifty ablation zones (one ablation zone in each rabbit) were produced in 50 rabbits using one or two 16-guage wet electrodes with a 1-cm active tip. The RFA system used in the monopolar and dual electrode wet bipolar RFA consisted of a 375-kHz generator (Elektrotom HiTT 106, Berchtold, Medizinelektronik, Germany). The power used was 30 watts and the exposure time was 5 minutes. The rabbits were assigned to one of five groups. Group A (n = 10) was infused with 0.9% NaCl used at a rate of 30 ml/hr in a monopolar mode. Groups B (n = 10) and C (n = 10) were infused with 0.9% NaCl at a rate of 15 and 30 ml/hr, respectively in dual electrode bipolar mode; groups D (n = 10) and E (n = 10) were infused with 5.8% NaCl at a rate of 15 and 30 ml/hr, respectively in a dual electrode bipolar mode. The dimensions of the ablation zones in the gross specimens from the groups were compared using one-way analysis of variance by means of the Scheffe test (post-hoc testing). RESULTS: The mean largest diameter of the ablation zones was larger in dual electrode bipolar mode (30.9+/-4.4 mm) than in monopolar mode (22.5+/-3.5 mm). The mean smallest diameter of the ablation zones was larger in dual electrode bipolar mode (22.3+/-2.5 mm) than in monopolar mode (19.5+/-3.5 mm). There were significant differences in the largest and smallest dimension between the monopolar (group A) and dual electrode wet bipolar mode (groups B-E). In dual electrode bipolar mode, the mean largest diameter of the ablation zones was larger at an infusion rate of 15 ml/hr (34.2+/-4.0 mm) than at 30 ml/hr (27.6+/-0.1 mm), and the mean smallest diameter of the ablation zones was larger at an infusion rate of 15 ml/hr (27.2+/-7.5 mm) than at an infusion rate of 30 ml/hr (24+/-2.9 mm). CONCLUSION: Using a wet electrode, dual electrode bipolar RFA can create a larger ablation zone more efficiently than monopolar RFA.

Keyword

Lung, interventional procedures; Radio-frequency ablation; Experimental study

MeSH Terms

Sodium Chloride/administration & dosage
Rabbits
Pulmonary Alveoli/pathology
Necrosis
Lung Neoplasms/surgery
Equipment Design
*Electrodes
Catheter Ablation/*instrumentation/methods
Animals

Figure

• 

  Fig. 1 CT scans and pathology findings of the spherical ablation zones in groups A, C and E. A, B. Non-contrast CT scans after RFA using the dual wet electrode showed a 15×11 mm, 10×9 mm ellipsoidal consolidation (arrows) with ill-defined margins in the right lower lung field and mild peripheral ground glass opacity. C, D. Gross specimen (C) shows a central dark area within the ablation zone between the two electrodes (arrow). Microscopic specimen (D) findings shows severe destruction, hemorrhage and complete necrosis of the normal lung structure in the center (arrow). The peripheral region showed incomplete necrosis of the normal lung parenchyma with an alveolar structure maintained without a hyalinized alveolar wall, no infiltration of the inflammatory cell, weak eosinophilic infiltration, and proteinous material within the alveoli (arrowheads).

• 

  Fig. 2 CT scans and pathology findings of the tumbling doll shape ablation zone in groups B and D. A, B. The non-contrast CT scans after RFA using a dual wet electrode showed a 12×10 mm , 8×7 circle consolidation (arrows) with an ill-defined margin in right lower lung and extensive peripheral ground-glass opacity. C, D. The ablation zones show two areas of coagulation necroses. The one electrode (arrow) creats larger ablation zone and the other (arrowhead) creats smaller ablation zone. Microscopic specimens show that larger ablation zone (L in D) has more severe hemorrhage and parenchymal destruction than smaller ablation zone (S in D).

• 

  Fig. 3 Measurement of the ablation zone. There was a significant difference in the Da and Dt between the monopolar and dual bipolar wet electrode mode.

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