Spontaneous breathing vs. mechanical ventilation for respiratory-gated MR-HIFU ablation in the liver

Background/introduction Magnetic resonance-guided High Intensity Focused Ultrasound (MR-HIFU) ablation in the liver is complicated by the continuous motion of the target due to the respiratory cycle. Several motion compensation strategies have been proposed in the past, such as breathholding, respiratory gating and dynamic beam steering. Respiratory gating for sonication and MR thermometry uses a pencil beam navigator on the diaphragm to limit power output and image acquisition to the resting phase of the diaphragm. Previously, we have used General Anesthesia with mechanical ventilation (GA) to obtain a long and reproducible resting phase of the diaphragm. From a patient’s perspective however, Procedural Sedation and Analgesia (PSA) has several advantages over GA such as a lower risk of complications and shorter recovery. In addition, it has lower associated costs and can be performed by nonanesthesiologists. The purpose of this animal study was to investigate the feasibility of respiratory-gated MR-HIFU ablation in the liver under PSA with spontaneous breathing.