Feasibility of synthetic CT images for robotic pedicle screw planning and navigation

Spinal robotic guidance platforms, which rely on computed tomography (CT) or cone beam CT (CBCT)-based navigation, enable precise preoperative planning and intraoperative placement of pedicle screws. However, they also result in significant radiation exposure to both patients and clinical staff. A recently FDA- and CE-approved high-resolution synthetic computed tomography (sCT) technology allows the generation of CT-equivalent images from magnetic resonance imaging (MRI) data, potentially reducing radiation exposure.

To assess the feasibility of using MRI-derived sCT images for pedicle screw planning and robotic navigation, and to compare patient radiation doses between standard CT-based and sCT-based workflows.

Twelve patients scheduled for thoracolumbar pedicle screw fixation underwent 3T MRI with additional T1-weighted 3D dual-echo gradient-echo (GRE) sequences. These GRE datasets were converted into sCT images using BoneMRI^® v1.8 (MRIguidance B.V.) and imported into the MAZOR™ robotic guidance system for preoperative planning, sCT-to-fluoroscopy fusion, and intraoperative navigation. Radiation doses were estimated using Monte Carlo-based NCICT and NCIRF dosimetry models, and compared to those from conventional CT-based workflows.

sCT images were visually comparable to conventional CT and fully compatible with the robotic navigation platform for both planning and execution. Replacing CT with sCT reduced patient radiation exposure by 98%, with residual dose primarily resulting from intraoperative fluoroscopy used for image fusion and verification.

MRI-derived sCT offers a radiation-free alternative to conventional CT for spinal robotic guidance, enabling pedicle screw planning and navigation while eliminating CT-associated radiation exposure.