High spatial resolution diffusion weighted imaging on clinical 3 T MRI scanners using multislab spiral acquisitions

Abstract

, "High spatial resolution diffusion weighted imaging on clinical 3 T MRI scanners using multislab spiral acquisitions," J. Med. Imag. 3(2), 023501 (2016) Abstract. A diffusion weighted imaging (DWI) approach that is signal-to-noise ratio (SNR) efficient and can be applied to achieve sub-mm resolutions on clinical 3 T systems was developed. The sequence combined a multislab, multishot pulsed gradient spin echo diffusion scheme with spiral readouts for imaging data and navigators. Long data readouts were used to keep the number of shots, and hence total imaging time, for the three-dimensional acquisition short. Image quality was maintained by incorporating a field-inhomogeneity-corrected image reconstruction to remove distortions associated with long data readouts. Additionally, multiple shots were required for the high-resolution images, necessitating motion induced phase correction through the use of efficiently integrated navigator data. The proposed approach is compared with two-dimensional (2-D) acquisitions that use either a spiral or a typical echo-planar imaging (EPI) acquisition to demonstrate the improved SNR efficiency. The proposed technique provided 71% higher SNR efficiency than the standard 2-D EPI approach. The adaptability of the technique to achieve high spatial resolutions is demonstrated by acquiring diffusion tensor imaging data sets with isotropic resolutions of 1.25 and 0.8 mm. The proposed approach allows for SNR-efficient sub-mm acquisitions of DWI data on clinical 3 T systems.

Structural and Functional MRI Evidence for Distinct Medial Temporal and Prefrontal Roles in Context-dependent Relational Memory

“…High-resolution DTI data were acquired using a 3-D multi-slab, multishot spiral sequence designed to achieve high spatial resolution through optimized signal-to-noise efficiency and reduced distortion artifacts (Holtrop & Sutton, 2016;Johnson et al, 2014). Imaging parameters included 30 encoding directions at b value = 1000 sec/mm 2 , 2 encodings at b value = 0 sec/mm 2 , repetition time/echo time = 1875/82 msec, field of view = 240 × 240 mm 2 , matrix = 150 × 150, 2 in-plane spiral shots (parallel imaging R = 2); 15 slabs with 4 slices per slab.…”

High‐resolution in vivo diffusion imaging of the human brain with generalized slice dithered enhanced resolution: Simultaneous multislice (gSlider‐SMS)

“…A major hurdle in performing submillimeter isotropic resolution dMRI is its inherently low signal-to-noise (SNR). Recently, simultaneous multislice (SMS) (6)(7)(8)(9)(10)(11) and 3D multislab (12)(13)(14)(15) acquisitions have been developed to improve dMRI's SNR efficiency. Conventional slice-by-slice dMRI exhibits long repetition times (TRs) as a result of the lengthy diffusion encoding that is repeated for each imaging slice.…”

Diffusion Imaging in the Post HCP Era

“…6 Inference across the candidate acquisition options demonstrated that a single low to medium b-value was sufficient for second fiber detection only, but that low b-value in combination with high b-values was necessary to resolve threeway crossings; in such a multishell (ie, multi b-value) diffusion encoding, the difference between shells had to be larger than 750 s/mm 2 to significantly aid in third fiber detection. These guidelines and experimental evaluations performed with pilot data supported a proposed three-shell acquisition in the young-adult WU-Minn HCP with b = 1000, 2000, 3000 s/mm 2 and Δb = 1000 s/mm 26 ; because of the shorter total scan times needed in the Lifespan HCP, the dMRI FIGURE 8: Sensitivity of different q-space sampling schemes in resolving (two-and three-way) crossing fibers within the centrum semiovale. The amount of crossings resolved by each scheme is normalized by the maximum.…”

“…The HCP Lifespan, where the dMRI resolution is 1.5 mm isotropic and 4-fold slice acceleration is employed, achieves a shorter TR (3200 msec) (Table 1), 12 which is still longer than the optimal TR. Thus, TR and volume acquisition times (VAT), 1 which are the same in a slice-based imaging approach, are suboptimal in the HCP; reducing this parameter towards the optimal value requires both reducing TE and increasing image accelerations, irrespective of the imaging approach used, whether slice-based as in the HCP or segmented 3D EPI or spiral trajectory acquisitions (eg, 20,[24][25][26] ) that are gradually being explored as an alternative. This in turn requires major new developments in hardware as well as image acquisition and reconstruction strategies, which are increasingly a major focus of the post-HCP era in the development of dMRI as well as fMRI techniques.…”