Electromagnetic Navigation System-Guided Microwave Ablation of Hepatic Tumors: A Matched Cohort Study.

Abstract

To assess the accuracy and applicability of an electromagnetic navigation system (EMNS) for CT-guided microwave ablation (MWA) of hepatic tumors in comparison with conventional CT-guidance. 34 patients (m = 20/f = 14, mean age 34y) with 34 liver tumors (primary = 22, metastases = 14, mean size 20mm) referred for CT-guided MWA were included in this IRB-approved study. Interventions were performed prospectively using an EMNS in 17 patients (navigation group), and results were compared to a matched historic cohort of 17 patients using conventional CT-guidance (control group, t-test, p < 0.05 deemed significant). Primary outcome measurement: accuracy of antenna placement (deviation). Secondary outcome measurements: setup time, number of control scans, duration and radiation exposure for antenna placement. Ablations were performed using a single or a double-angulated approach. Application of the EMNS was feasible in 14 cases (82%). Mean total deviation of the antenna feed point in the navigation and control group was 2.4mm (range 0.2-4.8mm) and 3.9mm (range 0.4-7.8mm), p < 0.05. Mean setup time for the EMNS was 6.75 ± 3.9min (range 3-12min). Mean number of control scans in the navigation and control group was 3 ± 0.9 (range 1-4) and 6 ± 1.3 (range 4-8), p < 0.0001; mean time for antenna placement was 9 ± 7.3min (range 1.4-25.9min) and 11.45 ± 6.1min (range 3.9-27.4min), p = 0.3164. Radiation exposure was significantly less in the navigation group. Our experience in a limited number of patients suggests that EMNS enables intuitive CT-guided MWA of liver tumors with higher accuracy when compared to ablations performed without navigation and with fewer control scans needed.