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A comparative experimental study of the in-vitro efficiency of hypertonic saline-enhanced hepatic bipolar and monopolar radiofrequency ablation.

Lee JM, Han JK, Kim SH, Sohn KL, Lee KH, Ah SK, Choi BI - Korean J Radiol (2003 Jul-Sep)

Bottom Line: The dimensions of the thermal ablation zones and changes in impedance and wattage during RFA were compared between the groups.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 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) Using an open perfusion system, HS-enhanced bipolar RFA more efficiently created larger areas of thermal ablation and higher tissue temperatures than monopolar RFA.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. leejm@radcom.snu.ac.kr

ABSTRACT

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.

Materials and 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)

Conclusion: Using an open perfusion system, HS-enhanced bipolar RFA more efficiently created larger areas of thermal ablation and higher tissue temperatures than monopolar RFA.

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Related in: MedlinePlus

General setting in monopolar and bipolar radiofrequency ablation in an in-vitro bovine liver model.A. Berchtold® radio-frequency system in monopolar mode (groups A and B). An open perfused electrode and injector were used for the continuous injection of hypertonic saline. Impedance, accumulated energy and power were continuously monitored by a generator. A thermocouple was inserted 15 mm from an electrode.B. Berchtold® radio-frequency system in bipolar mode (group C). Two pumps were employed to infuse hypertonic saline solution into the tissue. Note that a thermocouple was inserted midway between the two electrodes.
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Figure 1: General setting in monopolar and bipolar radiofrequency ablation in an in-vitro bovine liver model.A. Berchtold® radio-frequency system in monopolar mode (groups A and B). An open perfused electrode and injector were used for the continuous injection of hypertonic saline. Impedance, accumulated energy and power were continuously monitored by a generator. A thermocouple was inserted 15 mm from an electrode.B. Berchtold® radio-frequency system in bipolar mode (group C). Two pumps were employed to infuse hypertonic saline solution into the tissue. Note that a thermocouple was inserted midway between the two electrodes.

Mentions: For monopolar RFA, the distance between the electrodes and the dispersive metallic pad was set at 35 cm. Following the procedure of a previous experimental study by Gangi et al. (unpublished data, ECR 2003), two electrodes were placed in the liver, 3 cm apart, through an acryl plate containing multiple holes at 5-mm intervals. RF power was increased manually to 50 watts, and RF energy was applied sequentially for five or ten minutes in the monopolar mode by changing the current flow to the second probe just after ablation with the first. In this mode, current flows from one electrode to a dispersive metallic pad (Figs. 1A, B).


A comparative experimental study of the in-vitro efficiency of hypertonic saline-enhanced hepatic bipolar and monopolar radiofrequency ablation.

Lee JM, Han JK, Kim SH, Sohn KL, Lee KH, Ah SK, Choi BI - Korean J Radiol (2003 Jul-Sep)

General setting in monopolar and bipolar radiofrequency ablation in an in-vitro bovine liver model.A. Berchtold® radio-frequency system in monopolar mode (groups A and B). An open perfused electrode and injector were used for the continuous injection of hypertonic saline. Impedance, accumulated energy and power were continuously monitored by a generator. A thermocouple was inserted 15 mm from an electrode.B. Berchtold® radio-frequency system in bipolar mode (group C). Two pumps were employed to infuse hypertonic saline solution into the tissue. Note that a thermocouple was inserted midway between the two electrodes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2698083&req=5

Figure 1: General setting in monopolar and bipolar radiofrequency ablation in an in-vitro bovine liver model.A. Berchtold® radio-frequency system in monopolar mode (groups A and B). An open perfused electrode and injector were used for the continuous injection of hypertonic saline. Impedance, accumulated energy and power were continuously monitored by a generator. A thermocouple was inserted 15 mm from an electrode.B. Berchtold® radio-frequency system in bipolar mode (group C). Two pumps were employed to infuse hypertonic saline solution into the tissue. Note that a thermocouple was inserted midway between the two electrodes.
Mentions: For monopolar RFA, the distance between the electrodes and the dispersive metallic pad was set at 35 cm. Following the procedure of a previous experimental study by Gangi et al. (unpublished data, ECR 2003), two electrodes were placed in the liver, 3 cm apart, through an acryl plate containing multiple holes at 5-mm intervals. RF power was increased manually to 50 watts, and RF energy was applied sequentially for five or ten minutes in the monopolar mode by changing the current flow to the second probe just after ablation with the first. In this mode, current flows from one electrode to a dispersive metallic pad (Figs. 1A, B).

Bottom Line: The dimensions of the thermal ablation zones and changes in impedance and wattage during RFA were compared between the groups.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 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) Using an open perfusion system, HS-enhanced bipolar RFA more efficiently created larger areas of thermal ablation and higher tissue temperatures than monopolar RFA.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. leejm@radcom.snu.ac.kr

ABSTRACT

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.

Materials and 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)

Conclusion: Using an open perfusion system, HS-enhanced bipolar RFA more efficiently created larger areas of thermal ablation and higher tissue temperatures than monopolar RFA.

Show MeSH
Related in: MedlinePlus