Respiratory motion control during stereotactic thermal ablation of malignant liver tumors: clinical solutions to a technical problem

Percutaneous thermal ablation is a minimally invasive treatment option for select liver tumors. Stereotactic guidance for percutaneous thermal ablation depends on reliable respiratory motion control to maintain a consistent liver location and shape throughout the procedure for image acquisition and ablation probe placements. This is necessary to achieve accurate ablation probe placement and improve pre- to post-ablation image fusion for ablative margin assessment. In this prospective registry-based study, patients undergoing stereotactic percutaneous thermal ablation at a large academic cancer center in the United States between June 2023 and August 2024 were included. We compare lateral targeting errors between three subsequently introduced respiratory motion control techniques and investigated the influence of body mass index (BMI) on lateral targeting errors. In addition, we compare overall organ motion and deformation between intra-procedure pre- and post-ablation CT imaging using a biomechanical deformable image registration technique. We showed that High frequency jet ventilation resulted in higher targeting accuracy (3.7mm vs. 5.6 mm; p = 0.029) and mitigated the influence of BMI (r = -0.27 vs. r = 0.28) compared to breath holds with and without end tidal CO2 monitoring. Overall organ deformation between pre- and post-ablation CT imaging was not significantly reduced compared to breath holds (0.29 cm vs. 0.32 cm, p = 0.25). High frequency jet ventilation is the preferred option for respiratory motion control during stereotactic percutaneous thermal ablation of liver tumors. However, deformable image registration is still necessary for most cases for accurate assessment of sufficient ablative margins.