Motivation: High-field MRI (≥5 T) suffers from severe B0 inhomogeneities caused by magnetic susceptibility differences, especially in the inferior temporal cortices (ITCs), external auditory canals (EACs), and mastoid air cells (MACs). Goal(s): To address the localized bifocal B0 inhomogeneities around EACs and MACs, a novel local passive shim approach using ear shims was proposed and implemented. Approach: By optimizing the mass ratio of the biocompatible silicone/pyrolytic graphite (PG) mixture and incorporating additional embedded PG plates, the ΔB0 fields were significantly compensated. Results: In vivo experiments demonstrated a significant reduction in signal voids around EACs and MACs in GRE-echo echo planar imaging (EPI). Impact: The novel earplug enhances B0 homogeneity in the temporal lobe region, greatly improving the image quality of fMRI and supporting neuroscience research related to the temporal lobe region.
Liu et al. (Tue,) studied this question.