A comparative experimental study of the in-vitro efficiency of hypertonic saline-enhanced hepatic bipolar and monopolar radiofrequency ablation.
OBJECTIVE
To compare the in-vitro efficiency of a hypertonic saline (HS)-enhanced bipolar radiofrequency (RF) system with monopolar RF applications by assessing the temperature profile and dimensions of RF-created coagulation necrosis in bovine liver.


METHODS
A total of 27 ablations were performed in explanted bovine livers. After placement of two 16-gauge open-perfused electrodes at an interelectrode distance of 3 cm, 5% HS was instilled into tissue at a rate of 1 mL/min through the electrode. Seventeen thermal ablation zones were created in the monopolar mode (groups A, B), and ten more were created using the two open-perfused electrodes in the bipolar mode (group C). RF was applied to each electrode for 5 mins (for a total of 10 mins, group A) or 10 mins (for a total of 20 mins, group B) at 50W in the sequential monopolar mode, or to both electrodes for 10 min in the bipolar mode (group C). During RF instillation, we measured tissue temperature at the midpoint between the two electrodes. The dimensions of the thermal ablation zones and changes in impedance and wattage during RFA were compared between the groups.


RESULTS
With open-perfusion electrodes, the mean accumulated energy output value was lower in the bipolar mode (group C: 26675+/-3047 Watt s) than in the monopolar mode (group A: 28778+/-1300 Watt s) but the difference was not statistically significant (p > 0.05). In the bipolar mode, there were impedance rises of more than 700 ohm during RF energy application, but in the monopolar modes, impedance did not changed markedly. In the bipolar mode, however, the temperature at the mid-point between the two probes was higher (85 degrees C) than in the monopolar modes (65 degrees C, 80 degrees C for group A, B, respectively) (p < 0.05). In addition, in HS-enhanced bipolar RFA (group C), the shortest diameter at the midpoint between the two electrodes was greater than in either of the monopolar modes: 5.4+/-5.6 mm (group A); 28.8+/-8.2 mm (group B); 31.2+/-7.6 mm (group C) (p < 0.05)


CONCLUSIONS
Using an open perfusion system, HS-enhanced bipolar RFA more efficiently created larger areas of thermal ablation and higher tissue temperatures than monopolar RFA.
Lee
Jeong Min
JM
Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. leejm@radcom.snu.ac.kr
Han
Joon Koo
JK
Kim
Se Hyung
SH
Sohn
Kyu Li
KL
Lee
Kyoung Ho
KH
Ah
Su Kyung
SK
Choi
Byung Ihn
BI
D000818:Animals; D017115:Catheter Ablation / Q000379:methods; D002417:Cattle; D004566:Electrodes; D066298:In Vitro Techniques; D008099:Liver / Q000601:surgery*; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D013997:Time Factors
D012462:Saline Solution, Hypertonic