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Hepatic radiofrequency ablation using multiple probes: ex vivo and in vivo comparative studies of monopolar versus multipolar modes.

Lee JM, Han JK, Lee JY, Kim SH, Choi JY, Lee MW, Choi SH, Eo H, Choi BI - Korean J Radiol (2006 Apr-Jun)

Bottom Line: The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups.In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period.For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.

ABSTRACT

Objective: We wanted to compare the efficiency of multipolar radiofrequency ablation (RFA) using three perfused-cooled electrodes with multiple overlapping and simultaneous monopolar techniques for creating an ablation zone in ex vivo bovine livers and in in vivo porcine livers.

Materials and methods: In the ex vivo experiments, we used a 200 W generator (Valleylab, CC-3 model) and three perfused-cooled electrodes or internally cooled electrodes to create 30 coagulation zones by performing consecutive monopolar RFA (group A, n = 10), simultaneous monopolar RFA (group B, n = 10) or multipolar RFA (group C, n = 10) in explanted bovine livers. In the consecutive mode, three ablation spheres were created by sequentially applying 150 watts radiofrequency (RF) energy to the internally cooled electrodes for 12 minutes each for a total of 36 minutes. In the simultaneous monopolar and multipolar modes, RF energy was concurrently applied to the three perfused-cooled electrodes for 20 minutes at 150 watt with instillation of 6% hypertonic saline at 2 mL/min. During RFA, we measured the temperatures of the treated area at its center. The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups. In the in vivo experiments, three coagulations were created by performing multipolar RFA in a pig via laparotomy with using same parameter as the ex vivo study.

Results: In the ex vivo experiments, the impedance was gradually decreased during the RFA in groups B and C, but in group A, the impedance was increased during RFA and this induced activation by the pulsed RF technique. In groups A, B and C, the mean final-temperature values were 80+/-10 degrees C, 69+/-18 degrees C and 79+/-12 degrees C, respectively (p < 0.05). The multipolar mode created a larger volume of ablation than did the other modes: 37.6+/-4.0 cm3 (group A); 44.9+/-12.7 cm3 (group B); and 78.9+/-6.9 cm3 (group C) (p < 0.05). In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period. The mean volume of coagulations produced by multipolar RFA in the pig liver was 60.5+/-17.9 cm3.

Conclusion: For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.

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Related in: MedlinePlus

Graphs of mean temperatures at the center portion of the triangle that connected each electrode in each group. Note that higher temperatures occurred with the multipolar mode than with either the consecutive- or simultaneous-monopolar mode.
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Figure 4: Graphs of mean temperatures at the center portion of the triangle that connected each electrode in each group. Note that higher temperatures occurred with the multipolar mode than with either the consecutive- or simultaneous-monopolar mode.

Mentions: Compared with the simultaneous mode, the multipolar mode tended to produce round-shaped coagulation with a less prominent "waist" formation between the electrodes, i.e. the ratio of Dl/Dv was 1.6±0.4 in group B and it was 1.1±0.1 in group C (p < 0.05). There was a statistically significant difference in the Dl/Ds between groups B and C. Furthermore, the volumes of the ablation zones obtained with the consecutive, simultaneous and multipolar modes were 37.6±4 cm3, 44.9±12.7 cm3 and 78.9±6.9 cm3, respectively, and the differences in the volume of the ablation zones between the consecutive and multipolar modes or between the simultaneous and multipolar modes were statistically significant (p < 0.05). The graphs in Fig. 4 show the mean temperature at the center portion of the inserted electrodes. In groups A, B and C, the mean final-temperature values were 80±10℃, 69±18℃ and 79±12℃, respectively (p < 0.05)


Hepatic radiofrequency ablation using multiple probes: ex vivo and in vivo comparative studies of monopolar versus multipolar modes.

Lee JM, Han JK, Lee JY, Kim SH, Choi JY, Lee MW, Choi SH, Eo H, Choi BI - Korean J Radiol (2006 Apr-Jun)

Graphs of mean temperatures at the center portion of the triangle that connected each electrode in each group. Note that higher temperatures occurred with the multipolar mode than with either the consecutive- or simultaneous-monopolar mode.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2667583&req=5

Figure 4: Graphs of mean temperatures at the center portion of the triangle that connected each electrode in each group. Note that higher temperatures occurred with the multipolar mode than with either the consecutive- or simultaneous-monopolar mode.
Mentions: Compared with the simultaneous mode, the multipolar mode tended to produce round-shaped coagulation with a less prominent "waist" formation between the electrodes, i.e. the ratio of Dl/Dv was 1.6±0.4 in group B and it was 1.1±0.1 in group C (p < 0.05). There was a statistically significant difference in the Dl/Ds between groups B and C. Furthermore, the volumes of the ablation zones obtained with the consecutive, simultaneous and multipolar modes were 37.6±4 cm3, 44.9±12.7 cm3 and 78.9±6.9 cm3, respectively, and the differences in the volume of the ablation zones between the consecutive and multipolar modes or between the simultaneous and multipolar modes were statistically significant (p < 0.05). The graphs in Fig. 4 show the mean temperature at the center portion of the inserted electrodes. In groups A, B and C, the mean final-temperature values were 80±10℃, 69±18℃ and 79±12℃, respectively (p < 0.05)

Bottom Line: The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups.In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period.For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.

ABSTRACT

Objective: We wanted to compare the efficiency of multipolar radiofrequency ablation (RFA) using three perfused-cooled electrodes with multiple overlapping and simultaneous monopolar techniques for creating an ablation zone in ex vivo bovine livers and in in vivo porcine livers.

Materials and methods: In the ex vivo experiments, we used a 200 W generator (Valleylab, CC-3 model) and three perfused-cooled electrodes or internally cooled electrodes to create 30 coagulation zones by performing consecutive monopolar RFA (group A, n = 10), simultaneous monopolar RFA (group B, n = 10) or multipolar RFA (group C, n = 10) in explanted bovine livers. In the consecutive mode, three ablation spheres were created by sequentially applying 150 watts radiofrequency (RF) energy to the internally cooled electrodes for 12 minutes each for a total of 36 minutes. In the simultaneous monopolar and multipolar modes, RF energy was concurrently applied to the three perfused-cooled electrodes for 20 minutes at 150 watt with instillation of 6% hypertonic saline at 2 mL/min. During RFA, we measured the temperatures of the treated area at its center. The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups. In the in vivo experiments, three coagulations were created by performing multipolar RFA in a pig via laparotomy with using same parameter as the ex vivo study.

Results: In the ex vivo experiments, the impedance was gradually decreased during the RFA in groups B and C, but in group A, the impedance was increased during RFA and this induced activation by the pulsed RF technique. In groups A, B and C, the mean final-temperature values were 80+/-10 degrees C, 69+/-18 degrees C and 79+/-12 degrees C, respectively (p < 0.05). The multipolar mode created a larger volume of ablation than did the other modes: 37.6+/-4.0 cm3 (group A); 44.9+/-12.7 cm3 (group B); and 78.9+/-6.9 cm3 (group C) (p < 0.05). In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period. The mean volume of coagulations produced by multipolar RFA in the pig liver was 60.5+/-17.9 cm3.

Conclusion: For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.

Show MeSH
Related in: MedlinePlus