Korean J Radiol.  2016 Oct;17(5):742-749. 10.3348/kjr.2016.17.5.742.

Angled Cool-Tip Electrode for Radiofrequency Ablation of Small Superficial Subcapsular Tumors in the Liver: A Feasibility Study

• Park SI
• Kim IJ
• Lee SJ
• Shin MW
• Shin W
• Chung YE
• Kim GM
• Kim MD
• Won JY
• Lee DY
• Choi JS
• Han KH

• KMID: 2458066
• DOI: http://doi.org/10.3348/kjr.2016.17.5.742

Abstract

OBJECTIVE
To evaluate the feasibility of angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular liver tumors abutting abdominal wall, in order to traverse normal liver parenchyma, and thereby, obtain favorable configuration of ablation margin.
MATERIALS AND METHODS
In this study, we retrospectively analyzed 15 small superficial subcapsular liver tumors abutting abdominal wall in 15 patients, treated with radiofrequency ablation from March 2013 to June 2015 using a cool-tip electrode manually modified to create 25-35° angle at the junction between exposed and insulated segments. The tumors were hepatocellular carcinoma (n = 13) and metastases (n = 2: cholangiocellular carcinoma and rectosigmoid cancer), with maximum diameter of 10-26 mm (mean, 15.68 ± 5.29 mm). Under ultrasonographic guidance, the electrode tip was advanced to the depth of the tumors' epicenter about 1 cm from the margin. The tip was re-directed to penetrate the tumor for radiofrequency ablation. Minimal ablation margin was measured at immediate post-treatment CT. Radiological images and medical records were evaluated for success rate, length of minimal ablation margin and complications.
RESULTS
Technical success rate of obtaining complete necrosis of the tumors was 100%, with no procedure-related complication. Minimal ablation margin ranged from 3-12 mm (mean, 7.07 ± 2.23 mm). CT/MRI follow-up at 21-1022 days (mean, 519.47 ± 304.51 days) revealed no local recurrence, but distant recurrence in 9 patients.
CONCLUSION
Using an angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular tumors abutting abdominal wall may be a feasible technique for obtaining adequate ablation margin and lower complication rate.

Keyword

Radiofrequency ablation; Technique; Angled electrode; Hepatoma; Metastasis; Superficial; Subcapsular

MeSH Terms

Adult
Aged
Carcinoma, Hepatocellular/pathology/secondary/*surgery
Catheter Ablation/adverse effects/*instrumentation/methods
Electrodes
Equipment Design
Feasibility Studies
Female
Humans
Liver Neoplasms/pathology/*surgery
Magnetic Resonance Imaging
Male
Middle Aged
Neoplasm Recurrence, Local/surgery
Retrospective Studies
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Image of angled cool-tip electrode. Angled cool-tip electrode is prepared manually by applying 4 to 5, multiple small bends at junction of insulated segment and exposed segment of cooltip electrode to angle of 25–35° using sterile needle holder.

• 

  Fig. 2 Images of 49-year-old female with hepatocellular carcinoma during follow-up after two sessions of transarterial chemoembolization and RF ablation in other segment of liver. Dynamic liver MRI reveals recurrent hepatocellular carcinoma (white arrows) with early enhancement on arterial phase image (A) and high signal intensity on T2 weighted image (B) at superficial subcapsular region of segment 2. Sonography (C) obtained during RF ablation of hepatocellular carcinoma. Angled segment of cool-tip electrode (arrowheads) is inserted and advanced at approximately 45° to skin of access site and advanced toward capsule of liver apart from index tumor (arrows). Electrode (arrowhead) is penetrating liver capsule at about 1–2 cm apart from index tumor (arrows) (D). On entering liver parenchyma to about depth of index tumors' epicenter, tip of angled electrode (arrows) is directed toward index tumors' epicenter (E). Electrode is advanced to penetrate index tumor (arrows) until adequate position is obtained, and RF ablation is performed (F). Follow-up CT images performed immediately after (G) and 33 days after (H) RF ablation procedure reveals complete necrosis of tumor with sufficient ablation margin. RF = radiofrequency

• 

  Fig. 3 Diagram of difference between straight and angled cool-tip electrode. Junction of insulated and exposed segment of cool-tip electrode cannot be detected by ultrasonography. Even if junction is placed exactly at capsule of liver, ablation margin maybe insufficient in proximal electrode side (arrow) (A). When angled cool-tip electrode is used, angle can be detected on ultrasonography, and index tumor can be centered within exposed segment of electrode. Ablation margin will have more symmetric configuration around index tumor (B).

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