CT-guided radiofrequency liver tumour ablation: use of a two-step coaxial system with a fine guide needle wire unit for high-risk cases.

Accurate radiofrequency (RF) needle targeting to liver lesions under CT guidance is technically difficult and generally requires multiple needle manipulations, which carries potential risk. This approach is hardly applicable for precariously located lesions or for patients who have difficulty holding their breath. The aim of this study was to develop a novel two-step coaxial system to facilitate CT-guided RF ablation in difficult cases. The study group comprised 11 patients with 12 hepatic lesions. The coaxial system consisted of two parts: a 21-gauge pencil-tip guide needle wire (GNW) unit comprising a 150-mm-long needle segment and a 250-mm-long wire segment; and a 140-mm-long outer cannula with its stylet, which accepts a 17-gauge RF electrode needle. The GNW was inserted until the route of the GNW was confirmed to be positioned correctly. The cannula with the stylet was then advanced along the GNW. Lesions were successfully accessed using the GNW, even in patients who could not hold their breath, and manipulation was feasible within the limited space of the CT gantry. The light GNW also facilitated step-by-step CT-guided angular manipulations, unlike heavy RF electrodes, which are unstable during hands-free use unless deeply inserted. Therefore, this system enabled sequential ablations of large tumours by ensuring three different routes in advance by using the GNW. Insertion of the cannula along the GNW was simple. In conclusion, the two-step coaxial system enabled CT-guided RF tumour ablation to be performed in cases conventionally contraindicated owing to high risk of serious complications.