Motion- and field-robust mesoscopic whole-brain T2∗ -weighted imaging at 7T and 11.7T using servo navigation

Purpose: To mitigate artifacts related to motion and field changes in high-resolution T2*-weighted human brain imaging using servo navigation at ultra-high fields up to 11.7T. Methods: MR-based servo navigators were integrated into a segmented 3D-EPI sequence to allow for prospective correction of involuntary head motion and first-order shim changes. Seven subjects were scanned with whole-brain protocols at 0.3 mm isotropic resolution with and without correction at 7T and 11.7T. Validation was performed on detailed brain vasculature in scans with involuntary motion. Results: Blurring of small veins was reduced by servo navigation for all subjects and across field strengths. In case of involuntary large motion, the method preserved image quality, while uncorrected motion led to severe artifacts. In case of microscopic motion, reduced blurring and shading in the frontal lobe demonstrate the additional benefit of prospective field drift correction. Conclusion: Servo-navigated segmented 3D-EPI improves 0.3 mm isotropic whole-brain T2*-weighted imaging under realistic motion and field changes within 5.5 to 11 minutes scan time at 11.7 and 7T. KEYWORDS: servo navigation, prospective motion correction, mesoscopic imaging, 3D-EPI, 11.7T, brain vasculature