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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

Comparison of radiofrequency-induced coagulation created by applying radiofrequency in the three groups. Note that the mean shortest coagulation diameters midway between the two electrodes were largest in group C. Arrows indicate electrode tracks.A. Photograph of specimen from group AB. Photograph of specimen from group BC. Photograph of specimen from group C
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Figure 4: Comparison of radiofrequency-induced coagulation created by applying radiofrequency in the three groups. Note that the mean shortest coagulation diameters midway between the two electrodes were largest in group C. Arrows indicate electrode tracks.A. Photograph of specimen from group AB. Photograph of specimen from group BC. Photograph of specimen from group C

Mentions: After RFA, a well-defined area with central white discoloration was seen in the liver section of the ablated zones. The maximum overlapping width, measured in gross specimens of the three groups, was as follows: 40.4±7.8 mm in group A, 49.8±4.1 mm in group B, and 49.2±6.6 mm in group C (p < 0.05) (Table 1). In addition, the mean shortest coagulation diameters at the midpoint between the two electrodes were largest in group C: 5.4±5.6 mm in group A, 28.8±8.2 mm in group B, and 31.2±7.6 mm in group C. In groups B and C, the mean overlapping widths of the ablated spheres, measured along the two electrodes, and the shortest diameter, were larger than in group A (p < 0.05) (Fig. 4). Compared with monopolar RFA (group A), bipolar RFA (group C) therefore tended to produce oval-shaped coagulation with less prominent waist formation at the midpoint between the two electrodes (Table 1). Furthermore, bipolar RFA took less time than was required by monopolar RFA, group B, to produce similar coagulation necrosis, even though the energy output of the former was less than that of the latter (28778±1300 Watt·s vs. 26675±3047 Watt·s). Per unit of electrical energy used, bipolar RFA was thus more efficient.


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)

Comparison of radiofrequency-induced coagulation created by applying radiofrequency in the three groups. Note that the mean shortest coagulation diameters midway between the two electrodes were largest in group C. Arrows indicate electrode tracks.A. Photograph of specimen from group AB. Photograph of specimen from group BC. Photograph of specimen from group C
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Comparison of radiofrequency-induced coagulation created by applying radiofrequency in the three groups. Note that the mean shortest coagulation diameters midway between the two electrodes were largest in group C. Arrows indicate electrode tracks.A. Photograph of specimen from group AB. Photograph of specimen from group BC. Photograph of specimen from group C
Mentions: After RFA, a well-defined area with central white discoloration was seen in the liver section of the ablated zones. The maximum overlapping width, measured in gross specimens of the three groups, was as follows: 40.4±7.8 mm in group A, 49.8±4.1 mm in group B, and 49.2±6.6 mm in group C (p < 0.05) (Table 1). In addition, the mean shortest coagulation diameters at the midpoint between the two electrodes were largest in group C: 5.4±5.6 mm in group A, 28.8±8.2 mm in group B, and 31.2±7.6 mm in group C. In groups B and C, the mean overlapping widths of the ablated spheres, measured along the two electrodes, and the shortest diameter, were larger than in group A (p < 0.05) (Fig. 4). Compared with monopolar RFA (group A), bipolar RFA (group C) therefore tended to produce oval-shaped coagulation with less prominent waist formation at the midpoint between the two electrodes (Table 1). Furthermore, bipolar RFA took less time than was required by monopolar RFA, group B, to produce similar coagulation necrosis, even though the energy output of the former was less than that of the latter (28778±1300 Watt·s vs. 26675±3047 Watt·s). Per unit of electrical energy used, bipolar RFA was thus more efficient.

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