Magnetic resonance elastography of the human brain using a multiphase DENSE acquisition

Strasser, Johannes; Haindl, Michaela Tanja; Stollberger, Rudolf; Fazekas, Franz; Ropele, Stefan

doi:10.1002/mrm.27672

Cited by 10 publications

(10 citation statements)

References 16 publications

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“…Piezoelectric drivers allow to deliver arbitrary waveform pulses to tissues while avoiding the constraint of positioning relative to B 0 . Significant displacement fields could be obtained using this technique in various conditions (human abdomen [193,194], human brain [195,196], human breast [197], and mouse brain [198,199]). A major bottleneck in generating sufficiently high motion deflection in tissues is the decrease of the motion amplitude with increasing excitation frequencies.…”

Section: Generation Of Acoustic Waves In Mrementioning

confidence: 99%

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Flé

Bhatt

et al. 2021

Front. Phys.

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Changes in biomechanical properties of biological soft tissues are often associated with physiological dysfunctions. Since biological soft tissues are hydrated, viscoelasticity is likely suitable to represent its solid-like behavior using elasticity and fluid-like behavior using viscosity. Shear wave elastography is a non-invasive imaging technology invented for clinical applications that has shown promise to characterize various tissue viscoelasticity. It is based on measuring and analyzing velocities and attenuations of propagated shear waves. In this review, principles and technical developments of shear wave elastography for viscoelasticity characterization from organ to cellular levels are presented, and different imaging modalities used to track shear wave propagation are described. At a macroscopic scale, techniques for inducing shear waves using an external mechanical vibration, an acoustic radiation pressure or a Lorentz force are reviewed along with imaging approaches proposed to track shear wave propagation, namely ultrasound, magnetic resonance, optical, and photoacoustic means. Then, approaches for theoretical modeling and tracking of shear waves are detailed. Following it, some examples of applications to characterize the viscoelasticity of various organs are given. At a microscopic scale, a novel cellular shear wave elastography method using an external vibration and optical microscopy is illustrated. Finally, current limitations and future directions in shear wave elastography are presented.

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Section: Generation Of Acoustic Waves In Mrementioning

confidence: 99%

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Flé

Bhatt

et al. 2021

Front. Phys.

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“…However, for cerebral MRE, studies have also shown advantages using a relatively lower frequency, i.e. 10-20 Hz (Dittmann et al 2016, Strasser et al 2019 or ∼1 Hz (McGarry et al 2019, Zeng et al 2020). With a lower excitation frequency, less energy attenuation allows the waves to propagate through the deeper brain tissue while the longer encoding times result in higher motion sensitivities.…”

Section: Introductionmentioning

confidence: 99%

Fast magnetic resonance elastography with multiphase radial encoding and harmonic motion sparsity based reconstruction

Wang¹,

Chen²,

Li³

et al. 2022

Phys. Med. Biol.

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Objective: To achieve fast magnetic resonance elastography (MRE) at a low frequency for better shear modulus estimation of the brain. Approach: We proposed a multiphase radial DENSE MRE (MRD-MRE) sequence and an improved GRASP algorithm utilizing the sparsity of the harmonic motion (SH-GRASP) for fast MRE at 20 Hz. For the MRD-MRE sequence, the initial position encoded by one spatial modulation of magnetization (SPAMM) was decoded by an arbitrary number of readout blocks without increasing the number of phase offsets. Based on the harmonic motion, a modified total variation and temporal Fourier transform were introduced to utilize the sparsity in the temporal domain. Both phantom and brain experiments were carried out and compared with that from multiphase Cartesian DENSE-MRE (MCD-MRE), and conventional gradient echo sequence (GRE-MRE). Reconstruction performance was also compared with GRASP and compressed sensing. Main results: Results showed the scanning time of a fully sampled image with four phase offsets for MRD-MRE was only 1/5 of that from GRE-MRE. The wave patterns and estimated stiffness maps were similar to those from MCD-MRE and GRE-MRE. With SH-GRASP, the total scan time could be shortened by additional 4 folds, achieving a total acceleration factor of 20. Better metric values were also obtained using SH-GRASP for reconstruction compared with other algorithms. Significance: The MRD-MRE sequence and SH-GRASP algorithm can be used either in combination or independently to accelerate MRE, showing the potentials for imaging the brain as well as other organs.

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“…Then, encoding strategies that do not use oscillating gradients were also proposed. For instance, a displacement encoding with stimulated echoes (DENSE) Elastography sequence 22 , 23 was proposed to encode low frequency motion in tissues exhibiting short T2 values. Short encoding gradients that are independent of the excitation wave period are used, enabling short TEs.…”

Section: Introductionmentioning

confidence: 99%

Short echo time dual-frequency MR Elastography with Optimal Control RF pulses

Sango-Solanas

Koon

Reeth

et al. 2022

Sci Rep

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Magnetic Resonance Elastography (MRE) quantifies the mechanical properties of tissues, typically applying motion encoding gradients (MEG). Multifrequency results allow better characterizations of tissues using data usually acquired through sequential monofrequency experiments. High frequencies are difficult to reach due to slew rate limitations and low frequencies induce long TEs, yielding magnitude images with low SNR. We propose a novel strategy to perform simultaneous multifrequency MRE in the absence of MEGs: using RF pulses designed via the Optimal Control (OC) theory. Such pulses control the spatial distribution of the MRI magnetization phase so that the resulting transverse magnetization reproduces the phase pattern of an MRE acquisition. The pulse is applied with a constant gradient during the multifrequency mechanical excitation to simultaneously achieve slice selection and motion encoding. The phase offset sampling strategy can be adapted according to the excitation frequencies to reduce the acquisition time. Phantom experiments were run to compare the classical monofrequency MRE to the OC based dual-frequency MRE method and showed excellent agreement between the reconstructed shear storage modulus G′. Our method could be applied to simultaneously acquire low and high frequency components, which are difficult to encode with the classical MEG MRE strategy.

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Magnetic resonance elastography of the human brain using a multiphase DENSE acquisition

Cited by 10 publications

References 16 publications

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Viscoelasticity Imaging of Biological Tissues and Single Cells Using Shear Wave Propagation

Fast magnetic resonance elastography with multiphase radial encoding and harmonic motion sparsity based reconstruction

Short echo time dual-frequency MR Elastography with Optimal Control RF pulses

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