Mapping the human connectome using diffusion MRI at 300 mT/m gradient strength: Methodological advances and scientific impact

High‐fidelity, high‐spatial‐resolution diffusion magnetic resonance imaging of ex vivo whole human brain at ultra‐high gradient strength with structured low‐rank echo‐planar imaging ghost correction

“…30 There are now four Siemens 3-T Connectom scanners equipped with a maximum gradient strength of 300 mT/m in the world (Boston, Cardiff, Leipzig, and Shanghai). 31 General Electric currently offers several high-performance gradient systems such as the Microstructure Anatomy Gradient for Neuroimaging with Ultrafast Scanning (MAGNUS) head-only coil system, 32 which is capable of achieving 200 mT/m maximum gradient strength. New MR systems capable of gradient strengths up to 500 mT/m are being constructed and will soon be fully operational, enabling unprecedented studies of the micro-, meso-, and macro-connectome in the living human brain.…”

High Angular Resolution Susceptibility Imaging and Estimation of Fiber Orientation Distribution Functions in Primate Brain

“…Scanning of hominid whole-brain specimens requires large magnet bores and is technically more challenging, but also particularly interesting due to their more complex WM architecture. Resolutions around 500 µm seem to be the current limit with available hardware in such experiments (Eichner et al, 2020; Fan et al, 2022). In comparison, QSM acquisitions are less demanding on the hardware, and the signal loss at TEs in the order of 25 ms at 3 T or 12 ms at 7 T that are required for sufficient phase evolution is smaller than that inherent to DWI.…”

“…All MRI experiments were performed at 3 T on a MAGNETOM Skyra Connectom A (Siemens Healthineers, Erlangen, Germany) that achieves a maximum gradient strength of 300 mT/m (Fan et al, 2022). In order to avoid damage to the gradient coil during long scanning sessions, a first-order approximation of the acoustic response was computed in Matlab from the simulated gradient time course (IDEA DSV file) of each individual imaging protocol with its specific acquisition parameters (Labadie et al, 2013) and carefully inspected for potentially harmful vibrations.…”

“…In previous post-mortem experiments in mice Liu et al, 2012) and also in humans (Alkemade et al, 2020;2022), the problem of inconsistent deformations was avoided by keeping the fixed brain within the skull after surgical separation of the head. In the current work, a specific brain mask was derived from the 3D 𝑇 1 -weighted dataset and a custom-made container was designed consisting of an inner and an outer part (Figure 1B-E).…”

Connectome 2.0: Developing the next-generation ultra-high gradient strength human MRI scanner for bridging studies of the micro-, meso- and macro-connectome

“…Toward this goal, the Connectome 2.0 project targets the development of the next-generation human connectomics and microstructure MRI scanner, tailored for inferring cellular and axonal size and morphology at unprecedented spatial and diffusion resolution throughout the whole brain, while providing greater sensitivity and imaging speed for structural imaging at multiple scales in living human subjects. This transformative advance in imaging the micro-, meso- and macroscopic structure of the living human brain builds on the experience of engineering the first human MRI scanner equipped with 300 mT/m gradients, the strongest gradients developed for a human scanner to date, which was installed at the Massachusetts General Hospital (MGH) in 2011 as part of the Human Connectome Project (HCP) ( Setsompop et al, 2013 ) and has since been successfully disseminated to at least three other sites worldwide ( Jones et al, 2018 ), as discussed in greater extent in a separate review article included in this special issue ( Fan et al, 2021 ). The original Connectome scanner leveraged such high gradient strengths to enable high-sensitivity, high b -value diffusion MRI (dMRI), with the express purpose of mapping the major white matter pathways in the living human brain through diffusion tractography.…”