Fast submillimeter diffusion MRI using gSlider‐SMS and SNR‐enhancing joint reconstruction

Abstract

Purpose:We evaluate a new approach for achieving diffusion MRI data with high spatial resolution, large volume coverage, and fast acquisition speed. Theory and Methods: A recent method called gSlider-SMS enables whole-brain submillimeter diffusion MRI with high signal-to-noise ratio (SNR) efficiency.However, despite the efficient acquisition, the resulting images can still suffer from low SNR due to the small size of the imaging voxels. This work proposes to mitigate the SNR problem by combining gSlider-SMS with a regularized SNR-enhancing reconstruction approach. Results: Illustrative results show that, from gSlider-SMS data acquired over a span of only 25 minutes on a 3T scanner, the proposed method is able to produce 71 MRI images (64 diffusion encoding orientations with b = 1500 s/mm 2 , and 7 images without diffusion weighting) of the entire in vivo human brain with nominal 0.66 mm spatial resolution. Using data acquired from 75 minutes of acquisition as a gold standard reference, we demonstrate that the proposed SNR-enhancement procedure leads to substantial improvements in estimated diffusion parameters compared to conventional gSlider reconstruction. Results also demonstrate that the proposed method has advantages relative to denoising methods based on low-rank matrix modeling. A theoretical analysis of the trade-off between spatial resolution and SNR suggests that the proposed approach has high efficiency.Conclusions: The combination of gSlider-SMS with advanced regularized reconstruction enables high-resolution quantitative diffusion MRI from a relatively fast acquisition. K E Y W O R D Sconstrained reconstruction, denoising, diffusion MRI, fast imaging, high resolution

Transferring principles of solid-state and Laplace NMR to the field of in vivo brain MRI

“…Most clinical MRI applications rely on detecting 1 H nuclei of water molecules to produce three-dimensional images with a spatial resolution on the millimeter scale. Even though the attainable resolution is clearly insufficient for direct observation of indi-vidual cells, chemical and microstructural features can be investigated by probing their effect on magnetic resonance observables such as nuclear relaxation rates (Halle, 2006) and the translational diffusivity (Le Bihan, 1995) of water. Relaxation and diffusion parameters can thus indirectly report on various microscopic properties, including cell density (Padhani et al, 2009), orientation of nerve fibers , and the presence of nutrients (Daoust et al, 2017).…”

QSM Reconstruction Challenge 2.0: a realistic in silico head phantom for MRI data simulation and evaluation of susceptibility mapping procedures

“…At 3T resolutions below 1.5mm isotropic are not commonly obtained in vivo (as a reference, a one hour acquisition is used in the human connectome project to a achieve a 1.25mm isotropic resolution(50)). One avenue to obtain higher resolution DWI data are novel 3D multi-slab acquisition with gradient or rf encoding (51,52) that have significant SNR improvements in respect to conventional 2D-SMS as used in this work. Here we have simply interpolated our 1.5mm DWI to the anatomical space and expect this to be sufficient to develop and validate QSM methods that account for microstructural effects in white matter (53).…”

Motion‐robust sub‐millimeter isotropic diffusion imaging through motion corrected generalized slice dithered enhanced resolution (MC‐gSlider) acquisition

“…Because of this reason, the motion range of ±2 mm as investigated in the SNR&PSF analysis and phantom simulations is a representative ill‐conditioned motion range at the slab thickness of 4.3 mm used in the human studies. Future work will explore the incorporation of regularizations that also leverage joint information across diffusion encodings, such as the ones previously used to denoise and accelerate gSlider acquisitions (through interlaced subsampling of the RF‐encoding basis) . This should further improve MC‐gSlider reconstruction and enable motion‐robust reconstruction even in the case of single‐basis encoding.…”