Volume navigation

A senior interventional radiologist with 13 years of experience in RFA (>1,000 cases of RFA, >200 cases of imaging fusion) and a junior interventional radiologist, who was less experienced, with 3 years of experience in RFA (>50 cases of RFA, >30 cases of imaging fusion), participated in this study. They performed more than 10 cases of RFA or biopsy with automatic registration for 3 months before enrolling patients to get used to the new automatic registration technique.
The RS80A US system (Samsung Medison, Seoul, Korea), which is capable of fusion imaging (S-Fusion, Samsung Medison) was adopted for automatic registration. The LOGIQ E9 US system (GE Healthcare), which is also capable of fusion imaging (Volume Navigation, GE Healthcare) was adopted for manual registration. These US systems were coupled with a magnetic field generator. Two electromagnetic position sensors were connected to a position sensing unit and were attached on a convex-type ultrasound transducer using a bracket. Both the transmitter and sensors were connected to a fully integrated position sensor unit embedded in the US unit (Ascension Technology, Shelburne, VT, USA). For the LOGIQ E9 US system, an active patient tracker (OmniTrax, CIVCO Medical Solution, Kalona, IA, USA) was attached on the left anterior chest wall of the patient to correct patient motion.

All RFA procedures were performed percutaneously under US guidance (LOGIQ E9 or LOGIQ E10, GE Healthcare) by five radiologists with at least three years of experience with RFA using a fusion imaging technique (volume navigation; GE Healthcare) [13 (link)]. The operators used various RFA systems (VIVA RFA System, STARmed; Jet-tip RFA System, RF Medical). An active-tip length-adjustable tip (Proteus RF Electrode; STARmed) or clustered separable electrodes (Octopus Electrode, STARmed) were used. For ICWT, one (Jet-tip, RF Medical) or two (Twin electrodes, RF Medical) electrodes were used [10 (link)].
The operators used the tumor puncturing or no-touch method based on their preference, tumor location, and tumor shape [4 (link)]. Tumor-puncturing RFA refers to conventional RFA in which the operator places one electrode across the center of the tumor or multiple electrodes at the periphery of the tumor. In no-touch RFA, the operator positions multiple electrodes outside the tumor [12 (link)]. The RF energy is then delivered by switching monopolar, switching bipolar, and/or combined modes [5 (link)8 (link)11 (link)].