Feasibility of Synthetic CT Images for Robotic Pedicle Screw Planning and Navigation

PURPOSE: Spinal robotic guidance platforms facilitate preoperative and intraoperative planning of pedicle screw placement, requiring either a preoperative computed tomography (CT) scan for CT-to-fluoroscopy image registration or an intraoperative CT scan — both causing substantial radiation exposure to both patient end medical staff. A recently FDA- and CE-approved high-resolution 3D synthetic computed tomography (sCT) technique enables conversion of magnetic resonance imaging (MRI) data into CT-equivalent images. AIMS: To evaluate whether sCT images are suitable for pedicle screw planning and navigation, and to compare patient radiation doses between standard CT-based and sCT-based workflows. METHODS: Ten patients scheduled for thoracolumbar pedicle screw fixation underwent standard 3T MRI of the spine with additional T1-weighted 3D dual-echo gradient-echo (GRE) sequences. GRE datasets were converted to sCT images using BoneMRI® v1.8 (MRIguidance B.V.) and uploaded to the MAZOR™ platform for preoperative screw planning, sCT-to-fluoroscopy fusion, and intraoperative navigation. Effective radiation doses were calculated using NCICT and NCIRF Monte Carlo–based dosimetry, and compared with standard workflows using pre- or intraoperative CT. RESULTS: In all cases, sCT image quality was visually comparable to conventional CT and fully compatible with spinal robotic guidance platforms planning and navigation. No additional imaging was required. Dose modeling showed that replacing CT with sCT eliminated 98% of patient radiation exposure, with most residual dose arising from intraoperative fluoroscopy in order to perform sCT-fluoroscopy matching and controlling screw placement. CONCLUSION: MRI-derived sCT images provide a viable alternative to conventional CT for pedicle screw planning, 2D–3D image fusion, and robotic navigation, offering complete elimination of CT-related radiation exposure.