Microimaging at 14 Tesla Using GESEPI for Removal of Magnetic Susceptibility Artifacts in T₂*-Weighted Image Contrast

In magnetic resonance imaging (MRI), T₂*-weighted contrast is significantly enhanced by extremely high magnetic field strength, offering broad potential applications. However, the T₂*-weighted image contrast distortion and signal loss artifact arising from discontinuities of magnetic susceptibility within and around the sample are also increased, limiting utilization of high field systems for T₂*-weighted contrast applications. Due to the B₀ dependence of the contrast distortions and signal losses, and the heterogeneity of magnetic susceptibility in biological samples, magnetic susceptibility artifacts worsen dramatically for in vivo microimaging at higher fields. Practical applications of T₂*-sensitive techniques enhanced by higher magnetic fields are therefore challenged. This report shows that magnetic susceptibility artifacts dominate T₂*-weighted image contrast at 14 T, and demonstrates that the GESEPI (gradient echo slice excitation profile imaging) technique effectively reduces or eliminates these artifacts at long TE in the highest field (14 T) currently available for ¹H imaging.