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Optimization of wet radiofrequency ablation using a perfused-cooled electrode: a comparative study in ex vivo bovine livers.

Lee JM, Han JK, Kim SH, Lee JY, Shin KS, Han CJ, Lee MW, Choi JI, Choi BI - Korean J Radiol (2004 Oct-Dec)

Bottom Line: The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups.During RFA, the mean tissue impedances in groups A (243+/-88 ohm) and C (252.5+/-108 ohm) were significantly higher than those in groups B (85+/-18.7 ohm), D (108.2+/-85 ohm), E (70.0+/-16.3 ohm), and F (66.5+/-7 ohm) (p < 0.05).The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520+/-425 mA in group A, 1163+/-34 mA in group B, 652.5+/-418 mA in group C, 842.5+/-773 mA in group D, 1665+/-295 mA in group E, and 1830+/-109 mA in group F.

View Article: PubMed Central - PubMed

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

ABSTRACT

Objective: To determine the optimized protocol for wet monopolar radiofrequency ablation (RFA) using a perfused-cooled electrode to induce coagulation necrosis in the ex vivo bovine liver.

Materials and methods: Radiofrequency was applied to excised bovine livers in a monopolar mode using a 200W generator with an internally cooled electrode (groups A and B) or a perfused-cooled electrode (groups C, D, E, and F) at maximum power (150-200 W) for 10 minutes. A total of 60 ablation zones were created with six different regimens: group A-dry RFA using intra-electrode cooling; group B-dry RFA using intra-electrode cooling and a pulsing algorithm; group C-wet RFA using only interstitial hypertonic saline (HS) infusion; group D-wet RFA using interstitial HS infusion and a pulsing algorithm; group E-wet RFA using interstitial HS infusion and intra-electrode cooling; and group F-wet RFA using interstitial HS infusion, intra-electrode cooling and a pulsing algorithm. In groups C, D, E, and F, RFA was performed with the infusion of 6% HS through the perfused cooled electrode at a rate of 2 mL/minute. During RFA, we measured the tissue temperature at a distance of 15 mm from the electrode. The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups.

Results: During RFA, the mean tissue impedances in groups A (243+/-88 ohm) and C (252.5+/-108 ohm) were significantly higher than those in groups B (85+/-18.7 ohm), D (108.2+/-85 ohm), E (70.0+/-16.3 ohm), and F (66.5+/-7 ohm) (p < 0.05). The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520+/-425 mA in group A, 1163+/-34 mA in group B, 652.5+/-418 mA in group C, 842.5+/-773 mA in group D, 1665+/-295 mA in group E, and 1830+/-109 mA in group F. The mean volumes of the ablation regions in groups E and F were significantly larger than those in the other groups (p < 0.05): 17.7+/-5.6 cm(3) in group A, 34.5+/-3.0 cm(3) in group B, 20.2+/-15.6 cm(3) in group C, 36.1+/-19.5 cm(3) in group D, 68.1+/-12.4 cm(3) in group E, and 79.5+/-31 cm(3) in group F. The final tissue temperatures at a distance of 15 mm from the electrode were higher in groups E and F than those in groups A, C, and D (p < 0.05): 50+/-7.5 degrees C in group A, 66+/-13.6 degrees C in group B, 60+/-13.4 degrees C in group C, 61+/-12.7 degrees C in group D, 78+/-14.2 degrees C in group E, and 79+/-12.0 degrees C in group F.

Conclusion: Wet monopolar RFA, using intra-electrode cooling and interstitial saline infusion, showed better performance in creating a large ablation zone than either dry RFA or wet RFA without intra-electrode cooling.

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Photograph of a perfused-cooled electrode equipped for saline interstitial infusion on one side.
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Figure 1: Photograph of a perfused-cooled electrode equipped for saline interstitial infusion on one side.

Mentions: The RF system used in this study was a CC-3 Radionics generator that produces a maximum power of 200 W in association with a 17-gauge internally cooled electrode or a 15-gauge prototype perfused-cooled electrode with a 3 cm long active tip. As described in a previous study (28), we developed a prototype perfused-cooled electrode which allows both intra-electrode cooling and tissue hypertonic saline (HS) infusion to be performed simultaneously. To accomplish this, we modified an existing internally cooled electrode with a 3-cm active tip (Radionics) by covering it with a 15-gauge electrically insulated metal outer sheath, at a distance of up to 3.5 cm from the electrode tip (Fig. 1). The space between the 15-gauge sheath and the internally cooled electrode allowed for the saline infusion along the electrode. For wet RFA, 6% HS was infused at a rate of 2 mL/minute through the perfused-cooled electrode using an infusion pump (Pilotec IS; Fresenius Medical Care, Alzenau, Germany).


Optimization of wet radiofrequency ablation using a perfused-cooled electrode: a comparative study in ex vivo bovine livers.

Lee JM, Han JK, Kim SH, Lee JY, Shin KS, Han CJ, Lee MW, Choi JI, Choi BI - Korean J Radiol (2004 Oct-Dec)

Photograph of a perfused-cooled electrode equipped for saline interstitial infusion on one side.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2698169&req=5

Figure 1: Photograph of a perfused-cooled electrode equipped for saline interstitial infusion on one side.
Mentions: The RF system used in this study was a CC-3 Radionics generator that produces a maximum power of 200 W in association with a 17-gauge internally cooled electrode or a 15-gauge prototype perfused-cooled electrode with a 3 cm long active tip. As described in a previous study (28), we developed a prototype perfused-cooled electrode which allows both intra-electrode cooling and tissue hypertonic saline (HS) infusion to be performed simultaneously. To accomplish this, we modified an existing internally cooled electrode with a 3-cm active tip (Radionics) by covering it with a 15-gauge electrically insulated metal outer sheath, at a distance of up to 3.5 cm from the electrode tip (Fig. 1). The space between the 15-gauge sheath and the internally cooled electrode allowed for the saline infusion along the electrode. For wet RFA, 6% HS was infused at a rate of 2 mL/minute through the perfused-cooled electrode using an infusion pump (Pilotec IS; Fresenius Medical Care, Alzenau, Germany).

Bottom Line: The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups.During RFA, the mean tissue impedances in groups A (243+/-88 ohm) and C (252.5+/-108 ohm) were significantly higher than those in groups B (85+/-18.7 ohm), D (108.2+/-85 ohm), E (70.0+/-16.3 ohm), and F (66.5+/-7 ohm) (p < 0.05).The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520+/-425 mA in group A, 1163+/-34 mA in group B, 652.5+/-418 mA in group C, 842.5+/-773 mA in group D, 1665+/-295 mA in group E, and 1830+/-109 mA in group F.

View Article: PubMed Central - PubMed

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

ABSTRACT

Objective: To determine the optimized protocol for wet monopolar radiofrequency ablation (RFA) using a perfused-cooled electrode to induce coagulation necrosis in the ex vivo bovine liver.

Materials and methods: Radiofrequency was applied to excised bovine livers in a monopolar mode using a 200W generator with an internally cooled electrode (groups A and B) or a perfused-cooled electrode (groups C, D, E, and F) at maximum power (150-200 W) for 10 minutes. A total of 60 ablation zones were created with six different regimens: group A-dry RFA using intra-electrode cooling; group B-dry RFA using intra-electrode cooling and a pulsing algorithm; group C-wet RFA using only interstitial hypertonic saline (HS) infusion; group D-wet RFA using interstitial HS infusion and a pulsing algorithm; group E-wet RFA using interstitial HS infusion and intra-electrode cooling; and group F-wet RFA using interstitial HS infusion, intra-electrode cooling and a pulsing algorithm. In groups C, D, E, and F, RFA was performed with the infusion of 6% HS through the perfused cooled electrode at a rate of 2 mL/minute. During RFA, we measured the tissue temperature at a distance of 15 mm from the electrode. The dimensions of the ablation zones and the changes in impedance, currents, and liver temperature during RFA were compared between these six groups.

Results: During RFA, the mean tissue impedances in groups A (243+/-88 ohm) and C (252.5+/-108 ohm) were significantly higher than those in groups B (85+/-18.7 ohm), D (108.2+/-85 ohm), E (70.0+/-16.3 ohm), and F (66.5+/-7 ohm) (p < 0.05). The mean currents in groups E and F were significantly higher than those in groups B and D, which were significantly higher than those in groups A and C (p < 0.05): 520+/-425 mA in group A, 1163+/-34 mA in group B, 652.5+/-418 mA in group C, 842.5+/-773 mA in group D, 1665+/-295 mA in group E, and 1830+/-109 mA in group F. The mean volumes of the ablation regions in groups E and F were significantly larger than those in the other groups (p < 0.05): 17.7+/-5.6 cm(3) in group A, 34.5+/-3.0 cm(3) in group B, 20.2+/-15.6 cm(3) in group C, 36.1+/-19.5 cm(3) in group D, 68.1+/-12.4 cm(3) in group E, and 79.5+/-31 cm(3) in group F. The final tissue temperatures at a distance of 15 mm from the electrode were higher in groups E and F than those in groups A, C, and D (p < 0.05): 50+/-7.5 degrees C in group A, 66+/-13.6 degrees C in group B, 60+/-13.4 degrees C in group C, 61+/-12.7 degrees C in group D, 78+/-14.2 degrees C in group E, and 79+/-12.0 degrees C in group F.

Conclusion: Wet monopolar RFA, using intra-electrode cooling and interstitial saline infusion, showed better performance in creating a large ablation zone than either dry RFA or wet RFA without intra-electrode cooling.

Show MeSH
Related in: MedlinePlus