Fiducial marker–guided microwave ablation of liver tumors occult on conventional ablation-guidance imaging: A prospective single-center technical feasibility study

Backgrounds/Aims: Some liver tumors are visible on dynamic magnetic resonance imaging (MRI) yet remain occult on ultrasound (US), non-enhanced computed tomography (CT), US-CT/MRI fusion imaging, and contrast-enhanced US, which precludes image-guided ablation. We report a prospective single-center feasibility study of percutaneous gold fiducial tagging undertaken to enable microwave ablation (MWA) of such lesions. Methods: Of 168 patients (204 lesions) referred for hepatic ablation between January 2024 and March 2025, 25 lesions in 20 patients were occult on all four modalities and were enrolled. A single gold fiducial was implanted under US guidance one day before ablation using MRI-derived anatomic landmarks. Post-placement imaging characterized the three-dimensional fiducial-to-lesion offset and thereby provided a calibrated targeting vector for MWA. Technical success was defined as complete lesion coverage with a ≥ 5 mm circumferential margin on post-procedure imaging. Results: All 25 fiducials were placed without complications (median fiducial-to-lesion distance 8 mm, range 2-19). MWA was technically successful in 25 of 25 lesions (100%), and an independently confirmed ≥ 5 mm margin was achieved in every case. No procedure-related complications occurred and no local tumor progression was detected over a median follow-up of 21 months (range 12-30). Conclusions: Percutaneous gold fiducial tagging with vector-guided MWA is a feasible and reproducible strategy for ablating liver tumors that are occult on conventional planning modalities, achieving high targeting reproducibility and early local control in a selected cohort.