Feasibility of Using Ultra-High Field (7 T) MRI for Clinical Surgical Targeting

Abstract

The advantages of ultra-high magnetic field (7 Tesla) MRI for basic science research and neuroscience applications have proven invaluable. Structural and functional MR images of the human brain acquired at 7 T exhibit rich information content with potential utility for clinical applications. However, (1) substantial increases in susceptibility artifacts, and (2) geometrical distortions at 7 T would be detrimental for stereotactic surgeries such as deep brain stimulation (DBS), which typically use 1.5 T images for surgical planning. Here, we explore whether these issues can be addressed, making feasible the use of 7 T MRI to guide surgical planning. Twelve patients with Parkinson's disease, candidates for DBS, were scanned on a standard clinical 1.5 T MRI and a 7 T MRI scanner. Qualitative and quantitative assessments of global and regional distortion were evaluated based on anatomical landmarks and transformation matrix values. Our analyses show that distances between identical landmarks on 1.5 T vs. 7 T, in the mid-brain region, were less than one voxel, indicating a successful co-registration between the 1.5 T and 7 T images under these specific imaging parameter sets. On regional analysis, the central part of the brain showed minimal distortion, while inferior and frontal areas exhibited larger distortion due to proximity to air-filled cavities. We conclude that 7 T MR images of the central brain regions have comparable distortions to that observed on a 1.5 T MRI, and that clinical applications targeting structures such as the STN, are feasible with information-rich 7 T imaging.

Imaging for deep brain stimulation: The zona incerta at 7 Tesla

“…At 3 T MRI Balachandran et al [61] described the targeting error of T2-TSE in comparison to CT with a maximum of 0.13 mm over twelve targets. Duchin et al [62] compared T2-TSE at 7 T and 1.5 T and found distortion differences of less than one voxel size. At 7 T MRI Cho et al [27] quantified the geometrical distortions of a T2-weighted gradient-echo sequence with a mean deviation of 0.12 ± 0.13 mm.…”

Spatial Distortion in MRI-Guided Stereotactic Procedures: Evaluation in 1.5-, 3- and 7-Tesla MRI Scanners

“…Only limited literature is currently available regarding the use of 7-tesla MRI in stereotactic biopsies [17,18]. There is a presumption that the increased field strength increases the image distortion.…”

“…However, a good algorithm for automatic distortion correction is absent and, therefore, the application is currently not recommended even with CT fusion. The study by Duchin et al [17] compared 1.5- and 7-tesla MRI for clinical surgical targeting in 12 patients treated with deep brain stimulation for Parkinson's disease. Their analyses revealed that distances between identical landmarks on 1.5 vs. 7 T, in the mid-brain region, were <1 voxel and that the central part of the brain showed only minimal distortion.…”

Direct Visualization of Anatomic Subfields within the Superior Aspect of the Human Lateral Thalamus by MRI at 7T

“…However, it reduces the total error of the procedure and thus promotes a more comprehensive understanding of therapeutic outcomes. In that regard, 2 recent studies 29,30 investigated possible issues for neurosurgical targeting due to higher geometric distortions at 7T. Without dissent, they reported relatively small distortions in the central brain regions and concluded that targeting is feasible with 7T imaging.…”