Background: Fatigue is one of the most frequent and disabling symptoms in multiple sclerosis, but its pathophysiological mechanisms are poorly understood. It particular unclear whether how fatigue relates to structural functional brain changes. Objective: We aimed analyse association severity with basal ganglia connectivity, volumes, white matter integrity grey density. Methods: In 44 patients relapsing–remitting sclerosis 20 age- gender-matched healthy controls, resting-state fMRI,...

Purpose Viscoelastic properties of the liver are sensitive to fibrosis. This study proposes several modifications existing magnetic resonance elastography (MRE) techniques improve accuracy abdominal MRE. Methods The proposed method comprises following steps: (i) wave generation by a nonmagnetic, piezoelectric driver suitable for integration into patient table, (ii) fast single‐shot 3D wave‐field acquisition at four drive frequencies between 30 and 60 Hz, (iii) single‐step postprocessing...

Cerebral viscoelastic constants can be measured in a noninvasive, image-based way by magnetic resonance elastography (MRE) for the detection of neurological disorders. However, MRE brain maps are still limited low spatial resolution. Here we introduce three-dimensional multifrequency combined with novel reconstruction algorithm based on model-free inversion calculating spatially resolved parameter human corresponding to dynamic range shear oscillations between 30 and 60 Hz. Maps two...

Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity causes dispersion complex modulus, rendering recovered moduli frequency dependent. Therefore, we here propose use multifrequency data from magnetic resonance (MRE) solving inverse problem an algebraic...

Magnetic resonance elastography (MRE) is an increasingly used noninvasive modality for diagnosing diseases using the response of soft tissue to harmonic shear waves. We present a study on algebraic Helmholtz inversion (AHI) applied planar MRE, demonstrating that deduced phase speed waves depends strongly relative orientations actuator polarization, motion encoding direction and image plane as well plate size, signal-to-noise ratio discretization wave image. Results from numerical calculation...

The objective of this study was to introduce an magnetic resonance elastography (MRE) protocol based on fractional motion encoding and planar wave acquisition for rapid measurements in vivo human liver stiffness.Vibrations a remote actuator membrane were fed by rigid rod the patient's surface beneath right costal arch resulting axial shear deflections liver. Data performed using balanced steady-state free precession (bSSFP) sequence incorporating oscillating gradients sensitization. Tissue...

In vivo quantification of the anisotropic shear elasticity soft tissue is an appealing objective elastography techniques because elastic anisotropy can potentially provide specific information about structural alterations in diseased tissue. Here a method introduced and applied to MR (MRE) skeletal muscle. With this one elucidate by means two moduli (one parallel perpendicular muscle fiber direction). The technique based on group velocity inversion bulk waves, which achieved automatic...

An in vivo multifrequency magnetic resonance elastography (MRE) protocol was developed for studying the viscoelastic properties of human skeletal muscle different states contraction. Low-frequency shear vibrations range 25–62.5 Hz were synchronously induced into femoral muscles seven volunteers and measured a cross-sectional view by encoding fast-transverse wave component parallel to fibers. The so-called springpot model used deriving two constants, μ α, from dispersion functions complex...

Recent advances in dynamic elastography and biorheology have revealed that the complex shear modulus, G*, of various biological soft tissues obeys a frequency-dependent powerlaw. This viscoelastic powerlaw behavior implies mechanical properties are communicated tissue across continuum scales from microscopic to macroscopic. For deriving constitutive constants dispersion G* tissue, hierarchical fractal model is introduced accounts for multiscale networks. Effective-media derived by law based...

Purpose To assess if higher‐resolution magnetic resonance elastography (MRE) is a technique that can measure the in vivo mechanical properties of brain tissue and sensitive to early signatures degradation patients with clinically isolated syndrome (CIS). Materials Methods Seventeen CIS 33 controls were investigated by MRE 3T MRI scanner. Full‐wave field data acquired at seven drive frequencies from 30 60 Hz. The spatially resolved maps magnitude |G*| phase angle φ complex‐valued shear...

Presurgical, non-invasive methods of differentiating brain tumors have remained unsatisfactory even for specialized academic hospitals. Despite major advances in clinical and neuroradiological diagnostic techniques, the majority neurooncology patients still need to undergo a biopsy diagnosis. Recent single cell experiments suggested that biomechanical properties might be very sensitive detecting cellular malignancy. Accordingly, we investigated magnetic resonance elastography (MRE) as an...

Elasticity is a sensitive measure of the microstructural constitution soft biological tissues and increasingly used in diagnostic imaging. Magnetic resonance elastography (MRE) uniquely allows vivo measurement shear elasticity brain tissue. However, spatial resolution MRE inherently limited as transformation wave patterns into maps requires solution inverse problems. Therefore, an method introduced that avoids inversion instead exploits scattering at elastic interfaces between anatomical...

A method for direct determination of anisotropic elastic coefficients using two-dimensional shear wave patterns is introduced. Thereby, the symmetry approximated by a squared elliptic equation yielding an explicit relation between waveform and elasticity. The used to analyse MR elastography images biceps acquired continuous harmonic excitation at distal tendon muscle. Typically V-shaped were observed in this type tissue, which could be well reproduced proposed approximation assuming...

Objectives: To develop cardiac magnetic resonance elastography (MRE) for noninvasively measuring left ventricular (LV) pressure-volume (P-V) work. Material and Methods: The anterior chest wall of 8 healthy volunteers was vibrated by 24.3-Hz acoustic waves stimulating oscillating shear deformation in myocardium adjacent blood. induced motion recorded an electrocardiogram-gated, vibration-synchronized segmented gradient-recalled echo MRE sequence acquiring 360 phase-contrast wave images with a...

Abstract Purpose: To investigate the feasibility of quantitative in vivo ultrahigh field magnetic resonance elastography (MRE) human brain a broad range low‐frequency mechanical vibrations. Materials and Methods: Mechanical vibrations were coupled into healthy volunteer using coil‐driven actuator that either oscillated harmonically at single frequencies between 25 62.5 Hz or performed superimposed motion consisting multiple harmonics. Using sensitive single‐shot spin‐echo echo planar imaging...

Noninvasive image-based measurement of intrinsic tissue pressure is great interest in the diagnosis and characterization diseases. Therefore, we propose to exploit capability phase-contrast MRI measure three-dimensional vector fields motion for deriving volumetric strain induced by external vibration. Volumetric as given divergence mechanical displacement related compressibility thus sensitive state pressure. This principle demonstrated 50-Hz oscillations a compressible agarose phantom lungs...

The aim of this study was to introduce remote wave excitation for high‐resolution cerebral multifrequency MR elastography (mMRE). mMRE 25–45‐Hz drive frequencies by head rocker stimulation compared with based on a thorax mat in 12 healthy volunteers. Maps the magnitude | G *| and phase φ complex shear modulus were reconstructed using dual elasto‐visco (MDEV) inversion. After scan, subjects three operators assessed comfort convenience two methods stimulating brain. Images acquired coronal...

Magnetic resonance elastography (MRE) quantifies the shear modulus of biological tissue to detect disease. Complementary elastic properties tissue, compression may be a clinically useful biomarker because it is sensitive pressure and poromechanical interactions. In this work, we analyze capability MRE measure volumetric strain dynamic bulk (P-wave modulus) at harmonic drive frequency commonly used in shear-wave-based MRE. Gel phantoms with various densities were created by introducing...

A method based on magnetic resonance elastography is presented that allows measuring the weldedness of interfaces between soft tissue layers. The technique exploits dependence shear wave scattering at elastic frequency vibration. Experiments were performed gel phantoms including differently welded interfaces. Plane excitation parallel to planar interface with corresponding motion sensitization enabled observation only shear-horizontal (SH) scattering. Spatio-temporal filtering was applied...