Preoperative Magnetic Resonance and Intraoperative Computed Tomography Fusion for Real-Time Neuronavigation in Intramedullary Lesion Surgery

Image-guided surgery techniques in spinal surgery are usually based upon fluoroscopy or computed tomography (CT) scan, which allow for a real-time navigation of bony structures, though not of neural structures and soft tissue remains.

To verify the effectiveness and efficacy of a novel technique of imaging merging between preoperative magnetic resonance imaging (MRI) and intraoperative CT scan during removal of intramedullary lesions.

Ten consecutive patients were treated for intramedullary lesions using a navigation system aid. Preoperative contrast-enhanced MRI was merged in the navigation software, with an intraoperative CT acquisition, performed using the O-arm TM system (Medtronic Sofamor Danek, Minneapolis, Minnesota). Dosimetric and timing data were also acquired for each patient.

The fusion process was achieved in all cases and was uneventful. The merged imaging information was useful in all cases for defining the exact area of laminectomy, dural opening, and the eventual extension of cordotomy, without requiring exposition corrections. The radiation dose for the patients was 0.78 mSv. Using the authors' protocol, it was possible to merge a preoperative MRI with navigation based on intraoperative CT scanning in all cases. Information gained with this technique was useful during the different surgical steps. However, there were some drawbacks, such as the merging process, which still remains partially manual.

In this initial experience, MRI and CT merging and its feasibility were tested, and we appreciated its safety, precision, and ease.