The engineering of a 3T human MRI scanner equipped with 300 mT/m gradients – the strongest gradients ever built for an in vivo human MRI scanner – was a major component of the NIH Blueprint Human Connectome Project (HCP). This effort was motivated by the HCP’s goal of mapping, as completely as possible, the macroscopic structural connections of the in vivo healthy, adult human brain using diffusion tractography. Yet, the 300 mT/m gradient system is well suited to many additional types of diffusion measurements. Here, we present three initial applications of the 300mT/m gradients that fall outside the immediate scope of the HCP. These include: 1) diffusion tractography to study the anatomy of consciousness and the mechanisms of brain recovery following traumatic coma; 2) q-space measurements of axon diameter distributions in the in vivo human brain and 3) postmortem diffusion tractography as an adjunct to standard histopathological analysis. We show that the improved sensitivity and diffusion-resolution provided by the gradients is rapidly enabling human applications of techniques that were previously possible only for in vitro and animal models on small-bore scanners, thereby creating novel opportunities to map the microstructure of the human brain in health and disease.

Purpose To develop an efficient acquisition for high‐resolution diffusion imaging and allow in vivo whole‐brain acquisitions at 600‐ to 700‐μm isotropic resolution. Methods We combine blipped‐controlled aliasing in parallel imaging simultaneous multislice (SMS) with a novel slab radiofrequency (RF) encoding gSlider (generalized slice‐dithered enhanced resolution) to form a signal‐to‐noise ratio–efficient volumetric simultaneous multislab acquisition. Here, multiple thin slabs are acquired simultaneously with controlled aliasing, and unaliased with parallel imaging. To achieve high resolution in the slice direction, the slab is volumetrically encoded using RF encoding with a scheme similar to Hadamard encoding. However, with gSlider, the RF‐encoding bases are specifically designed to be highly independent and provide high image signal‐to‐noise ratio in each slab acquisition to enable self‐navigation of the diffusion's phase corruption. Finally, the method is combined with zoomed imaging (while retaining whole‐brain coverage) to facilitate low‐distortion single‐shot in‐plane encoding with echo‐planar imaging at high resolution. Results A 10‐slices‐per‐shot gSlider‐SMS acquisition was used to acquire whole‐brain data at 660 and 760 μm isotropic resolution with b‐values of 1500 and 1800 s/mm2, respectively. Data were acquired on the Connectome 3 Tesla scanner with 64‐channel head coil. High‐quality data with excellent contrast were achieved at these resolutions, which enable the visualization of fine‐scale structures. Conclusions The gSlider‐SMS approach provides a new, efficient way to acquire high‐resolution diffusion data. Magn Reson Med 79:141–151, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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