5 T In Vivo Head Imaging With Universal RF Shimming

ABSTRACT Purpose Brain MR imaging at 10.5 T ultra‐high field offers significant improvements in signal‐to‐noise ratio (SNR), but faces challenges with B 1 + inhomogeneity. Parallel‐transmission (pTx) can be used to achieve a more uniform RF field distribution, but necessitates the use of B 1 + calibration in the region of interest. This study explores a universal B 1 + shim solution on 10.5 T that could eliminate the need for time‐consuming subject‐specific B 1 + calibration. Methods B 1 + data from 7 participants (19 sessions) were used to develop the universal B 1 + shim, which was then validated against traditional subject‐specific approaches using T 1 ‐weighted MP2RAGE structural images in 5 participants (6 sessions). Statistical comparisons of tissue and subcortical segmentations were conducted using popular neuroimaging tools SPM and FreeSurfer, respectively. Results The universal shim rapidly converged with a small training dataset, likely due to consistent positioning and the simplicity of B 1 + shimming used for head imaging. Whole‐brain tissue segmentation showed no statistically significant differences between universal and subject‐specific solutions, with only minor variations near the ventricles and inferior brain regions in the detailed subcortical segmentation. The proposed universal B 1 + shim reduces examination time by removing the need for separate data acquisition and optimization. Conclusion These findings suggest that the universal B 1 + shim is a viable substitute for subject‐specific approaches, offering a more efficient solution for neuroimaging applications. Additionally, it confirms that 10.5 T MRI can produce reliable structural brain imaging data, paving the way for broader adoption of ultra‐high field MRI in neuroimaging research.