Abstract No. 71 Electromagnetic Navigation System with a Marker Software for Computed Tomography–Guided Microwave Ablation of Liver Tumors Undetectable in Scans without Contrast Medium Injection

This prospective study evaluated the feasibility and safety of percutaneous computed tomography (CT)-guided microwave ablation of hepatic tumors (which were undetectable in scans without intravenous contrast medium injection) using an electromagnetic navigation system with a marker software. The study included 21 patients (18/3 male/female, mean age 67.14±10.33) with 23 hepatic tumors (mean diameter, 14.57±4.23 mm). All patients have been eligible for the 6 months imaging follow-up post ablation. Neoplasmatic substrate included hepatocellular carcinoma (12/21 patients) and colorectal cancer metastasis (9/21 patients). Clinical efficacy was defined as complete tumor necrosis and was evaluated on contrast-enhanced MRI after 1, 3 and 6 months. Evaluated parameters included accuracy of probe placement, procedure duration, number of acquired computed tomography scans and adverse events. The microwave probe was placed in the tumor target and ablation was performed in all cases (technical success 100%). A double oblique out-of-plane approach was performed in 16/23 target tumors. Mean duration of the ablation sessions was 50.42±7.84 min. The mean trajectory length was 13.57±3.55 cm. The mean probe's tip-to marker's center distance was 1.14±1.06 mm. Median scans number performed during the ablation sessions was 7.71±1.60. No adverse events occurred. At 6 months imaging follow-up tumor remnant was noted in 1/23 lesions (primary clinical success 95.65%) which was re-successfully treated (secondary clinical success 100%). Percutaneous microwave ablation of hepatic tumors that cannot be seen on non- contrast computed tomography scans can be successfully and safely performed using an electromagnetic navigation system with marker software.