An Optimized System for Interventional Magnetic Resonance Imaging-Guided Stereotactic Surgery: Preliminary Evaluation of Targeting Accuracy

BACKGROUND: Deep brain stimulation electrode placement with interventional magnetic resonance imaging (MRI) has previously been reported using a commercially available skull-mounted aiming device (Medtronic Nexframe MR) and native MRI scanner software. This first-generation method has technical limitations that are inherent to the hardware and software used. A novel system (SurgiVision ClearPoint) consisting of an aiming device (SMARTFrame) and software has been developed specifically for interventional MRI, including deep brain stimulation. OBJECTIVE: To report a series of phantom and cadaver tests performed to determine the capability, preliminary accuracy, and workflow of the system. METHODS: Eighteen experiments using a water phantom were used to determine the predictive accuracy of the software. Sixteen experiments using a gelatin-filled skull phantom were used to determine targeting accuracy of the aiming device. Six procedures in 3 cadaver heads were performed to compare the workflow and accuracy of ClearPoint with Nexframe MR. RESULTS: Software prediction experiments showed an average error of 0.9 +/- 0.5 mm in magnitude in pitch and roll (mean pitch error, 20.2 +/- 0.7 mm; mean roll error, 0.2 +/- 0.7 mm) and an average error of 0.7 +/- 0.3 mm in X-Y translation with a slight anterior (0.5 +/- 0.3 mm) and lateral (0.4 +/- 0.3 mm) bias. Targeting accuracy experiments showed an average radial error of 0.5 +/- 0.3 mm. Cadaver experiments showed a radial error of 0.2 +/- 0.1 mm with the ClearPoint system (average procedure time, 88 +/- 14 minutes) vs 0.6 +/- 0.2 mm with the Nexframe MR (average procedure time, 92 +/- 12 minutes). CONCLUSION: This novel system provides the submillimetric accuracy required for stereotactic interventions, including deep brain stimulation placement. It also overcomes technical limitations inherent in the first-generation interventional MRI system.