3D multislab, multishot acquisition for fast, whole‐brain MR elastography with high signal‐to‐noise efficiency

Abstract

Purpose To develop an acquisition scheme for generating magnetic resonance elastography (MRE) displacement data with whole-brain coverage, high spatial resolution, and adequate signal-to-noise ratio (SNR) in a short scan time. Theory and Methods A 3D multislab, multishot acquisition for whole-brain MRE with 2.0 mm isotropic spatial resolution is proposed. The multislab approach allowed for the use of short repetition time to achieve very high SNR efficiency. High SNR efficiency allowed for a reduced acquisition time of only six minutes while the minimum SNR needed for inversion was maintained. Results The mechanical property maps estimated from whole-brain displacement data with nonlinear inversion (NLI) demonstrated excellent agreement with neuroanatomical features, including the cerebellum and brainstem. A comparison with an equivalent 2D acquisition illustrated the improvement in SNR efficiency of the 3D multislab acquisition. The flexibility afforded by the high SNR efficiency allowed for higher resolution with a 1.6 mm isotropic voxel size, which generated higher estimates of brainstem stiffness compared with the 2.0 mm isotropic acquisition. Conclusions The acquisition presented allows for the capture of whole-brain MRE displacement data in a short scan time, and may be used to generate local mechanical property estimates of neuroanatomical features throughout the brain.

Magnetic Resonance Elastography Demonstrating Low Brain Stiffness in a Patient with Low-Pressure Hydrocephalus: Case Report

“…Across the cerebrum, including all white and gray matter but excluding regions of CSF [6,8], her average stiffness was 1.62 kPa. This is approximately 46% softer than the normal brain that generally exhibits a stiffness of approximately 3.0 kPa in healthy populations at 50 Hz [6,9]. This patient had very low tissue stiffness, and thus very high tissue compliance, consistent with previous hypotheses of the causation and etiology of LPH.…”

“…The captured images are used to estimate mechanical properties of brain tissue through the finite element-based nonlinear inversion algorithm [10]. Specific details of imaging and inversion schemes are described in the previous works by Johnson et al [9] and McGarry et al [10], respectively.…”

“…Here the stiffness measure is analogous to tissue elasticity, which is the inverse of tissue compliance. The specific MRE scan protocol uses a 3-dimensional multislab, multishot spiral sequence for generating whole-brain displacement images at 2 mm isotropic resolution [9]. The captured images are used to estimate mechanical properties of brain tissue through the finite element-based nonlinear inversion algorithm [10].…”

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

“…Several recent approaches to address the challenges of SNR and artifacts have included specialized scanning hardware, pulse sequence modifications, and image reconstruction advances. [1][2][3][4] While many of the recent advances have focused on specialized hardware, the proposed approach will enable high resolution imaging on any hardware configuration. Achieving sufficient SNR for a high-resolution diffusion scan relies on minimizing the echo time (TE) and operating at an SNR-optimal repetition time (TR).…”

Shear Stiffness of 4 Common Intracranial Tumors Measured Using MR Elastography: Comparison with Intraoperative Consistency Grading

“…10,11,14,24 The recent development of a 3D multislab, multishot acquisition for whole-brain MRE could achieve high signal-to-noise efficacy. [25][26][27][28][29] 3D analysis could improve the results if the wave propagation is complicated, especially if there is throughplane oblique wave propagation that a 2D analysis would not visualize correctly.…”