Viscoelasticity of children and adolescent brains through MR elastography

Ozkaya, Efe; Fabris, Gloria; Macruz, Fabíola Bezerra de Carvalho; Suar, Zeynep M.; Abderezaei, Javid; Su, Bochao; Laksari, Kaveh; Wu, Lawrence Shih-Hsin; Camarillo, David B.; Pauly, Kim Butts; Wintermark, Max; Kurt, Mehmet

doi:10.1016/j.jmbbm.2020.104229

Cited by 17 publications

(18 citation statements)

References 65 publications

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“…It is imperative to determine that the actuator is operating at the correct frequency and with sufficient amplitude before use in the intended tissue. One method for determining this is to use, as an example, a laser Doppler vibrometer to achieve an accurate estimate of the unloaded actuator frequency and its frequency response (Curtis, Zhang, Khalilzad‐Sharghi, Boulet, & Othman, 2012; Ozkaya et al., 2021; Triolo et al., 2021). This method can also be used to determine the time delay from signal generator output to end‐effector vibration in the case of the pneumatic actuator (Triolo et al., 2021).…”

Section: Commentarymentioning

confidence: 99%

“…Additionally, because biological tissues exhibit viscoelastic behavior, the mechanical response of tissue is dependent on loading speed or, in the case of MRE, the frequency of actuation. Therefore, some studies use multifrequency MRE, in which the vibration is applied and encoded at different frequencies to determine viscoelasticity (Kurt et al., 2019; Lipp et al., 2013; Neumann et al., 2018; Ozkaya et al., 2021).…”

Section: Commentarymentioning

confidence: 99%

“…The main drawback of this type of device is that they are usually quite bulky and have difficulty attaching to the tissue (Tse et al., 2009). This type of actuator, particularly the piezoelectric type, is most commonly used for MRE of small animals or phantoms (Brauck et al., 2007; Meinhold et al., 2019; Namani et al., 2009; Ozkaya et al., 2021; Rossman et al., 2003; Uffmann et al., 2002; Yin et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

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Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

et al. 2022

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Magnetic resonance elastography (MRE) is a technique for determining the mechanical response of soft materials using applied harmonic deformation of the material and a motion‐sensitive magnetic resonance imaging sequence. This technique can elucidate significant information about the health and development of human tissue such as liver and brain, and has been used on phantom models (e.g., agar, silicone) to determine their suitability for use as a mechanical surrogate for human tissues in experimental models. The applied harmonic deformation used in MRE is generated by an actuator, transmitted in bursts of a specified duration, and synchronized with the magnetic resonance signal excitation. These actuators are most often a pneumatic design (common for human tissues or phantoms) or a piezoelectric design (common for small animal tissues or phantoms). Here, we describe how to design and assemble both a pneumatic and a piezoelectric MRE actuator for research purposes. For each of these actuator types, we discuss displacement requirements, end‐effector options and challenges, electronics and electronic‐driving requirements and considerations, and full MRE implementation. We also discuss how to choose the actuator type, size, and power based on the intended material and use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Design, construction, and implementation of a convertible pneumatic MRE actuator for use with tissues and phantom models Basic Protocol 2: Design, construction, and implementation of a piezoelectric MRE actuator for localized excitation in phantom models

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Section: Commentarymentioning

confidence: 99%

Section: Commentarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

et al. 2022

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“…Magnetic resonance elastography (MRE) is a phase contrast‐based MRI technology that can create whole‐brain mechanical property maps in vivo through mechanical vibration 1 . These mechanical properties have been related to development, 2,3 aging, 4–6 and neurodegenerative disease, 7–9 and show promise towards clinically assessing neural tissue health 10–13 . The MRE field has made substantial advances in data acquisition to improve resolution and imaging speed; however, these improvements are often limited by signal‐to‐noise ratio (SNR) and artifacts, including off‐resonance related geometric distortion.…”

Section: Introductionmentioning

confidence: 99%

Quantitative effects of off‐resonance related distortion on brain mechanical property estimation with magnetic resonance elastography

2021

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Off-resonance related geometric distortion can impact quantitative MRI techniques, such as magnetic resonance elastography (MRE), and result in errors to these otherwise sensitive metrics of brain health. MRE is a phase contrast technique to determine the mechanical properties of tissue by imaging shear wave displacements and estimating tissue stiffness through inverse solution of Navier's equation. In this study, we systematically examined the quantitative effects of distortion and corresponding correction approaches on MRE measurements through a series of simulations, phantom models, and in vivo brain experiments. We studied two different k-space trajectories, echo-planar imaging and spiral, and we determined that readout time, off-resonance gradient strength, and the combination of readout direction and off-resonance gradient direction, impact the estimated mechanical properties. Images were also processed through traditional distortion correction pipelines, and we found that each of the correction mechanisms works well for reducing stiffness errors, but are limited in cases of very large distortion. The ability of MRE to detect subtle changes to neural tissue health relies on accurate, artifactfree imaging, and thus off-resonance related geometric distortion must be considered when designing sequences and protocols by limiting readout time and applying correction where appropriate.

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“… 20 Most soft tissues in the body demonstrate viscoelastic properties that are subcategorized as “strain-stiffening materials”, where as the material stretches, it becomes effectively stiffer. 17–19,21 Loss moduli have been quantified for various tissues, including lung (∼600 Pa), 22 brain (∼1 kPa), 23 cornea (∼12 kPa), 24 and liver (∼17 kPa), 25 suggesting that the loss modulus of soft tissues varies greatly throughout the body.…”

Section: Introductionmentioning

confidence: 99%

Rheological characterization of poly-dimethyl siloxane formulations with tunable viscoelastic properties

et al. 2021

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Viscoelasticity of children and adolescent brains through MR elastography

Cited by 17 publications

References 65 publications

Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

Quantitative effects of off‐resonance related distortion on brain mechanical property estimation with magnetic resonance elastography

Rheological characterization of poly-dimethyl siloxane formulations with tunable viscoelastic properties

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