178 Utility of 7T Imaging for Deep Brain Stimulation Surgery

INTRODUCTION: Structural and functional MR images of the human brain acquired at 7 Tesla exhibit rich informational content with potential utility for clinical applications. However, (1) substantial increases in susceptibility artifact, and (2) the possibility of geometrical distortion at increased magnetic field strength, would be detrimental for stereotactic procedures such as deep brain stimulation (DBS) surgery, which typically use CT and/or 1.5T MR images for surgical planning. We address these two issues from a technical standpoint, demonstrating minimal distortion and artifact in the midbrain region, and supplement technical findings with the clinical aspects of our investigation. METHODS: Twelve candidates for DBS to treat Parkinson's disease were scanned pre-operatively on a standard clinical 1.5T MRI and a 7T MRI scanner. Qualitative and quantitative assessments of global and regional distortion were evaluated based on anatomical landmarks and transformation matrix values, and postoperative electrode location assessed relative to preoperative predictions made independently on 1.5 and 7T imaging. Postoperative CT and 1.5T MRI were then fused to preoperative datasets, and location of active contacts from postoperative DBS programming identified on 7T. RESULTS: Regional analysis demonstrated that the central portion of the brain showed sub-millimetric distortion, while inferior and frontal areas exhibited larger distortion due to proximity to air-filled cavities. Our analysis demonstrates (1) successful co-registration between 1.5T and 7T images, and (2) validates 7T-based predictions of ultimate electrode placement. CONCLUSION: 7T MR images of the midbrain region yield comparable distortion to that observed at 1.5T. Clinical applications targeting structures such as the STN, are feasible with the enhanced informational content provided by 7T imaging.