Purpose
: The purpose of this study is to assess the usefulness of new designed “ sheathed” cooled-perfusion(SCP) electrode with simultaneous hypertonic saline(HS) and acetic acid(AA) infusion in radiofrequency ablation(RFA) of bovine liver by comparing size and volume of ablation zone created with SCP electrode without HS and AA infusion.
Material and methods
Thirty ablation zones (group A: SCP electrode without perfusion materials, n = 10; group B: SCP electrode with 5.85% HS infusion, n = 10 ;group C: SCP electrode with 50% AA infusion, n = 10) were produced in explanted bovine livers under ultrasound guidance (a 12- minute ablation cycle; pulsed technique; 2,000 mA, maximum). The cooled electrode consisted of an internally cooled, 17-gauge electrode and stainless steel outer sheath (1.8 mm) with apertures(diameter 1.8mm) that has insulated except 2cm active tip. This coaxial system has the circulation of cooling water through the electrode using a peristaltic pump and sheath with separate apertures for interstitial infusion of HS and AA using another infusion pump at rate of 1ml/min.. After RFA, immediately MR imaging were obtained and then,in each group, maximum and minimum diameters of the ablation zones in the gross specimen and MR images and volume of ablation zones on the MR images were measured. The maximum diameter, minimum diameter, shape and the calculated volumes of ablation zones were compared with each group.
Results
Group B were significantly larger than those created with group A and group C for minimum diameter (5.4 ± 0.80 cm versus 2.4 ± 0.15 cm, 2.5 ± 0.67; P < .05), maximum diameter (5.8 ± 0.82 cm versus 3.0 ± 0.65, 3.9± 1.36 cm; P < .05) on gross specimen and volume (68.5 ± 26.17 cm3 versus 11.1 ± 3.69, 15.7± 11.88 cm3; P < .05) at MR imaging. The shapes of ablation zones on gross specimen were indistinguishable between group A and group B and ablation zones were near spherical.but shape of group C were not ovoid and margin of that was irregualr.
Conclusion
The new designed "sheathed" cooled -perfusion electrode with saline infusion could efficiently be used to increase the size of the ablation zone in liver , due to its use of simultaneous internal cooling and interstitial hypertonic saline infusion. Further in- vivo experimental investigations will be needed to optimize design and operational parameters .