Korean J Radiol.  2003 Mar;4(1):19-26. 10.3348/kjr.2003.4.1.19.

Radiofrequency Ablation of the Gastrointestinal Tract with a Stent-Like Electrode: Experimental Study

• Byun JN
• Kang SG
• Choi JY
• Kim DH
• Lee JM
• Kim YC
• Ki KH
• Lee CG

• KMID: 754038
• DOI: http://doi.org/10.3348/kjr.2003.4.1.19

Abstract

OBJECTIVE
To assess the technical feasibility of a newly designed stent-like electrode in rabbits. MATERIALS AND METHODS: A stent-like electrode was knitted from a single thread of nitinol wire and interconnected to a generator using similar wire. In order to gauge the extent of radiofrequency ablation (RFA), we measured the depth of the ablated area in cow liver using a combination of 180-sec time intervals and 20-watt power increments. For data processing, Cox regression analysis was used. RFA was also applied to the small intestine of rabbits using this stent-like electrode under six different sets of conditions: 10 watts for 1 min, 10 watts for 2 mins, 20 watts for 1 min, 20 watts for 2 mins, 30 watts for 1 min, and 30 watts for 2 mins. To determine the gross and microscopic findings, six animals were sacrificed immediately after the procedure and the results obtained under the different sets of conditions were correlated. Eight rabbits were monitored for 4 weeks prior to sacrifice. RESULTS: For both ex-vivo and in-vivo ablations, the depth of the thermal lesion showed linear correlation with both the duration of RFA and the power applied. RFA of the duodenum was technically successful in all 14 rabbits. The acute changes occurring in the rabbits' small intestine included color change, cytoplasmic denaturation, fibrin deposition and hemorrhage, among which hemorrhage of the mucosal layer was the earliest finding. RF ablation for 2 mins at 30 watts caused serosal hemorrhage. The gross and histologic changes occurring showed close correlation under all six sets of conditions. CONCLUSION: Use of the stent-like electrode proves technically feasible but to determine the nature of the chronic change occurring in the gastrointestinal tract after RF ablation, further investigation and long-term follow-up in animals are required.

Keyword

Gastrointestinal tract, interventional procedures; Interventional procedures, experimental studies; Radiofrequency (RF) ablation

Figure

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  Fig. 1 Photograph of the stent-like electrode, showing connection between the nitinol wire and adaptor (A); expanded stent-like electrode (B); connecting wire between the stent and generator, with insulation of this wire by a polyethylene tube (C).

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  Fig. 2 Diagram of the stent-like electrode system.

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  Fig. 3 Whole cow liver (A) was used for ex-vivo study. The stent-like electrode was introduced through the parenchymal tract (B); the electrode after ablation (C); sectioned liver shows an ovoid zone of ablation along the parenchymal tract (D).

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  Fig. 4 Conventional film obtained during RF ablation of the duodenum. A. First ablation, at distal duodenum. B. Second ablation, at more proximal duodenum. C. Third ablation, at proximal duodenum.

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  Fig. 5 Graph of time vs. depth of ablation, showing linear correlation between these two parameters.

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  Fig. 6 Graph of power applied vs. depth of ablation, showing linear correlation between these two parameters.

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  Fig. 7 Gross findings just after RF ablation. A. Minimal change is noted after 10 W / 1-min ablation (arrow). B. Dark-colored hematoma is noted after 20 W / 1-min ablation (arrow). C. Larger hematoma is noted after 30 W / 1-min ablation (arrow). D. Two-week follow-up after 20 W / 2-min ablation. The duodenum was perforated at three different sites, at which it adhered to adjacent organs such as the liver (large arrow), abdominal wall (arrowhead), and colon (small arrow).

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  Fig. 8 Histologic findings after ablation using various combinations of power and elapsed time. A. 30 W / 1-min. Hemorrhagic necrosis occurred in the lumen, but the lamina propria and serosa are intact. B. 60 W / 2-min. Hemorrhagic necrosis of the mucosa, lamina propria and serosa has occurred. C. Four-week follow-up, 20 W /1-min. A regenerated mucosal layer is apparent. D. Two-week follow-up, 20 W / 2-min. Granulation tissue, fibrinoid necrosis, neovascularization and inflammatory cell infiltration indicate ulcer formation. The bowel was perforated.

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