Tabletop magnetic resonance elastography for the measurement of viscoelastic parameters of small tissue samples

Ipek-Ugay, Selcan; Drießle, Toni; Ledwig, Michael; Guo, Jing; Hirsch, Sebastian; Sack, Ingolf; Braun, Jürgen

doi:10.1016/j.jmr.2014.11.009

Cited by 24 publications

(19 citation statements)

References 43 publications

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“…At 900 Hz a decaying wave with displacement in the range of 0.5–10 μm (mean 2 μm) was induced. This displacement amplitude is comparable to other MRE studies [87,92]. We observed that the MRE actuation system behaves frequency dependent; less power was needed with lower frequencies to generate sufficient displacement at the MRE piston.…”

Section: Discussionsupporting

confidence: 89%

“…At 60 and 90 min after indentation a trend of elevated G d was observed. The determined mean shear moduli values in non-damaged condition are in range with reported values of MRE measurements and ex vivo biomechanical tests [23,71,87–89]. These results show the high potential of the setup to measure non-invasively the quantitative mechanical properties related to deep tissue injury in vivo .…”

Section: Discussionsupporting

confidence: 81%

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A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

et al. 2017

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Deformation of skeletal muscle in the proximity of bony structures may lead to deep tissue injury category of pressure ulcers. Changes in mechanical properties have been proposed as a risk factor in the development of deep tissue injury and may be useful as a diagnostic tool for early detection. MRE allows for the estimation of mechanical properties of soft tissue through analysis of shear wave data. The shear waves originate from vibrations induced by an external actuator placed on the tissue surface. In this study a combined Magnetic Resonance (MR) compatible indentation and MR Elastography (MRE) setup is presented to study mechanical properties associated with deep tissue injury in rats. The proposed setup allows for MRE investigations combined with damage-inducing large strain indentation of the Tibialis Anterior muscle in the rat hind leg inside a small animal MR scanner. An alginate cast allowed proper fixation of the animal leg with anatomical perfect fit, provided boundary condition information for FEA and provided good susceptibility matching. MR Elastography data could be recorded for the Tibialis Anterior muscle prior to, during, and after indentation. A decaying shear wave with an average amplitude of approximately 2 μm propagated in the whole muscle. MRE elastograms representing local tissue shear storage modulus Gd showed significant increased mean values due to damage-inducing indentation (from 4.2 ± 0.1 kPa before to 5.1 ± 0.6 kPa after, p<0.05). The proposed setup enables controlled deformation under MRI-guidance, monitoring of the wound development by MRI, and quantification of tissue mechanical properties by MRE. We expect that improved knowledge of changes in soft tissue mechanical properties due to deep tissue injury, will provide new insights in the etiology of deep tissue injuries, skeletal muscle damage and other related muscle pathologies.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionsupporting

confidence: 81%

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

et al. 2017

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“…Anisotropic models require additional material parameters to be estimated while enforcing isotropy reduces the burden on the inversion of noisy data. Though recent work has aimed to estimate anisotropic tissue properties with MRE [11, 12, 13, 14, 17, 18, 19, 20], including specific WM tracts in the brain [7, 15, 21, 22, 23], the effect of WM anisotropy on traditional isotropic inversion schemes has yet to be fully characterized [24]. …”

Section: Introductionmentioning

confidence: 99%

Observation of direction-dependent mechanical properties in the human brain with multi-excitation MR elastography

Anderson

Houten

McGarry

et al. 2016

Journal of the Mechanical Behavior of Biomedical Materials

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Magnetic resonance elastography (MRE) has shown promise in noninvasively capturing changes in mechanical properties of the human brain caused by neurodegenerative conditions. MRE involves vibrating the brain to generate shear waves, imaging those waves with MRI, and solving an inverse problem to determine mechanical properties. Despite the known anisotropic nature of brain tissue, the inverse problem in brain MRE is based on an isotropic mechanical model. In this study, distinct wave patterns are generated in the brain through the use of multiple excitation directions in order to characterize the potential impact of anisotropic tissue mechanics on isotropic inversion methods. Isotropic inversions of two unique displacement fields result in mechanical property maps that vary locally in areas of highly aligned white matter. Investigation of the corpus callosum, corona radiata, and superior longitudinal fasciculus, three highly-ordered white matter tracts, revealed differences in estimated properties between excitations of up to 33%. Using diffusion tensor imaging to identify dominant fiber orientation of bundles, relationships between estimated isotropic properties and shear asymmetry are revealed. This study has implications for future isotropic and anisotropic MRE studies of white matter tracts in the human brain.

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“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19] In MRE, the sample is excited mechanically, and the response is measured with magnetic resonance imaging. The primary goal of the technique is early detection of tissue lesions by determining the elasticity coefficients from the wavelengths of the stress waves.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, MRE is a local measurement technique, and consequently, requires a lot of time to characterize a sample, as well as does not have sufficient spatial resolution to obtain a broad range of elasticity coefficients of gels. Braun et al 19 demonstrated the measurement of viscoelastic parameters of small tissue samples using a tabletop MRE with the resolution of 0.23 mm × 0.23 mm × 3 mm. On the other hand, Hu et al 20 used an optical imaging system (the shadowgraph method) with the resolution of under 50 µm to visualize the multiple stress waves generated by femtosecond laser ablation (LA) in silica glass.…”

Section: Introductionmentioning

confidence: 99%

High spatial and temporal resolution measurement of mechanical properties in hydrogels by non-contact laser excitation

et al. 2016

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Gels have received increased attention as potential materials for biological materials because they can exhibit similar mechanical properties. One obstacle for using gels is that their mechanical properties are significantly altered by defects, such as an inhomogeneous crosslink density distribution. If these defects could be detected and the values and spatial distributions of mechanical properties in the gel could be determined, it would be possible to apply gels for several fields. To achieve the high spatial and temporal resolution measurement of mechanical properties in hydrogels, in our method, a conventional contact excitation device is replaced with a non-contact excitation using laser ablation for the input and magnetic resonance elastography to measure stress waves is replaced with the Schlieren method with a high-speed camera. Magnetic resonance elastography is a local measurement technique, and consequently, requires a lot of time to characterize a sample, as well as does not have sufficient spatial resolution to obtain a broad range of elasticity coefficients of gels. We use laser ablation to apply non-contact impulse excitations to gels to generate stress waves inside them. We can determine mechanical properties of gels using the stress waves’ propagation velocity.

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Tabletop magnetic resonance elastography for the measurement of viscoelastic parameters of small tissue samples

Cited by 24 publications

References 43 publications

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

Observation of direction-dependent mechanical properties in the human brain with multi-excitation MR elastography

High spatial and temporal resolution measurement of mechanical properties in hydrogels by non-contact laser excitation

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