Human brain diffusion tensor imaging at submillimeter isotropic resolution on a 3 Tesla clinical MRI scanner

Abstract

The advantages of high-resolution diffusion tensor imaging (DTI) have been demonstrated in a recent post-mortem human brain study (Miller et al., NeuroImage 2011;57(1):167–181), showing that white matter fiber tracts can be much more accurately detected in data at submillimeter isotropic resolution. To our knowledge, in vivo human brain DTI at submillimeter isotropic resolution has not been routinely achieved yet because of the difficulty in simultaneously achieving high resolution and high signal-to-noise ratio (SNR) in DTI scans. Here we report a 3D multi-slab interleaved EPI acquisition integrated with multiplexed sensitivity encoded (MUSE) reconstruction, to achieve high-quality, high-SNR and submillimeter isotropic resolution (0.85 × 0.85 × 0.85 mm3) in vivo human brain DTI on a 3 Tesla clinical MRI scanner. In agreement with the previously reported post-mortem human brain DTI study, our in vivo data show that the structural connectivity networks of human brains can be mapped more accurately and completely with high-resolution DTI as compared with conventional DTI (e.g., 2 × 2 × 2 mm3).

3D-MB-MUSE: A robust 3D multi-slab, multi-band and multi-shot reconstruction approach for ultrahigh resolution diffusion MRI

“…Through a new model, termed 3D-MB-MUSE, image quality is ensured by reconstructing 3D ms-EPI data while simultaneously accounting for motion artifacts induced across different dimensions (in-plane and through-plane) throughout the acquisition of shots and kz-planes. In comparison, using the traditional 2D MUSE approach to reconstruct high-resolution 3D multi-shot dMRI data (Chang et al, 2015b) fails to appropriately account for both motion artifacts and coil sensitivity variations across the slice dimension of a relatively thin 3D slab (e.g. 10mm used in this report).…”

“…In the first data set, all shots in each kz-plane of the acquired 3D ms-EPI data were individually reconstructed with SENSE and combined through a complex average performed over shots. In the second data set, all kz-planes of the acquired 3D ms-EPI data were individually reconstructed with the 2D MUSE model, as in (Chang et al, 2015b). Finally, the kz-planes generated by both the SENSE and 2D MUSE reconstructions were converted to slice images through a 1D Fourier transform performed across kz.…”

“…(9) is reconstructed into un-aliased voxel values in all slices of all simultaneously excited slabs with both shot-to-shot and slab-encoding motion artifacts accounted for. It is of note that the 2D multi-band MUSE model (Chang et al, 2015b) is derived from Eq. (8) if N Z = N KZ =1, and the original 2D MUSE model (Chen et al, 2013) is derived when both N Z = N KZ =1 and N B =1.…”

High-resolution diffusion MRI at 7T using a three-dimensional multi-slab acquisition

“…The primary challenges include motion sensitivity and the reduced SNR at high spatial resolution, in which the latter is particularly problematic for diffusion MRI due to its low intrinsic SNR, which often means imaging near the noise floor. To improve the SNR of in vivo high-resolution diffusion MRI without substantially increasing the scan time, the two dominant approaches are the use of ultra-high field (7T and up) scanners (Heidemann et al, 2012, Eichner et al, 2014, Strotmann et al, 2014, Vu et al, 2015) and acquisition schemes with higher SNR per unit time compared to the current standard, two dimensional (2D) single-shot echo planar imaging (EPI) (Van et al, 2011, Setsompop et al, 2012a, Engstrom and Skare, 2013, Uğurbil et al, 2013, Frost et al, 2014, Chang et al, 2015). …”

“…A number of methods for reducing these artefacts have been proposed (Oshio et al, 1991, Parker et al, 1991, Murakami et al, 1995, Van et al, 2011, Engstrom and Skare, 2013, Frost et al, 2014, Chang et al, 2015), all of which increase scan time due to oversampling/overlapping of slabs, and often require a longer TR to reduce the saturation effects at slab boundaries (Engstrom et al, 2015). The slab profile encoding (PEN) method (Van et al, 2015) can correct the aliasing artefacts with minimal increase in scan time (except for a calibration scan), but exhibits residual artefacts below TR~4 s (Wu et al, 2015).…”