Magnetic resonance measurement of transient shear wave propagation in a viscoelastic gel cylinder

Bayly, Philip V.; Massouros, P.; Christoforou, Eftychios G.; Sabet, Arash A.; Genin, Guy M.

doi:10.1016/j.jmps.2007.10.012

Cited by 34 publications

(39 citation statements)

References 18 publications

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“…This invariant measure combines both principal strain components. Previous studies using this device reported radial-circumferential shear strain values because this component dominates the deformation, and has a clear physical interpretation, including the meaning of positive and negative values (Bayly et al, 2008; Sabet et al, 2008). For comparison, images of the raw radial-circumferential strain values for all experiments from the human subjects are provided in Supplemental Figures 4–6.…”

Section: Discussionmentioning

confidence: 99%

“…Prior to the experiment, the phantom was allowed to equilibrate to room temperature for at least 8 hours. The response of thegelatin cylinder to mild angular acceleration has previously been characterized using tagged MRI and compared to a numerical simulation (Bayly et al, 2008). Additionally, the gelatin phantom can be imaged for a longer period of time than human subjects.…”

Section: Methodsmentioning

confidence: 99%

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Improved measurement of brain deformation during mild head acceleration using a novel tagged MRI sequence

Knutsen

Magrath

McEntee

et al. 2014

Journal of Biomechanics

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In vivo measurements of human brain deformation during mild acceleration are needed to help validate computational models of traumatic brain injury and to understand the factors that govern the mechanical response of the brain. Tagged magnetic resonance imaging is a powerful, noninvasive technique to track tissue motion in vivo which has been used to quantify brain deformation in live human subjects. However, these prior studies required from 72 to 144 head rotations to generate deformation data for a single image slice, precluding its use to investigate the entire brain in a single subject. Here, a novel method is introduced that significantly reduces temporal variability in the acquisition and improves the accuracy of displacement estimates. Optimization of the acquisition parameters in a gelatin phantom and three human subjects leads to a reduction in the number of rotations from 72–144 to as few as 8for a single image slice. The ability to estimate accurate, well-resolved, fields of displacement and strain in far fewer repetitions will enable comprehensive studies of acceleration-induced deformation throughout the human brain in vivo.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Improved measurement of brain deformation during mild head acceleration using a novel tagged MRI sequence

Knutsen

Magrath

McEntee

et al. 2014

Journal of Biomechanics

View full text Add to dashboard Cite

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“…13). Images of gel deformation were obtained using an analytical model and solution described in Bayly et al (2007). The gel is intended only as a qualitative analog to the brain, but the shear moduli are within the range of values reported for fresh mammalian brain (e.g., Thibault and Margulies, 1998).…”

Section: Discussionmentioning

confidence: 99%

Deformation of the human brain induced by mild angular head acceleration

Sabet

Christoforou

Zatlin

et al. 2008

Journal of Biomechanics

174

146

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Deformation of the human brain was measured in tagged magnetic resonance images (MRI) obtained dynamically during angular acceleration of the head. This study was undertaken to provide quantitative experimental data to illuminate the mechanics of traumatic brain injury (TBI). Mild angular acceleration was imparted to the skull of a human volunteer inside an MR scanner, using a custom MR-compatible device to constrain motion. A grid of MR "tag" lines was applied to the MR images via spatial modulation of magnetization (SPAMM) in a fast gradient echo imaging sequence. Images of the moving brain were obtained dynamically by synchronizing the imaging process with the motion of the head. Deformation of the brain was characterized quantitatively via Lagrangian strain. Consistent patterns of radial-circumferential shear strain occur in the brain, similar to those observed in models of a viscoelastic gel cylinder subjected to angular acceleration. Strain fields in the brain, however, are clearly mediated by the effects of heterogeneity, divisions between regions of the brain (such as the central fissure and central sulcus) and the brain's tethering and suspension system, including the dura mater, falx cerebri, and tentorium membranes.

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“…HARP has been validated in synthetic images [19] and in a gel phantom under shear [20]. Normal strain mean and SD by segment were determined from volunteer images.…”

Section: Methodsmentioning

confidence: 99%

Ischemic Mitral Regurgitation: Abnormal Strain Overestimates Nonviable Myocardium

Morgan

Zhang

Tartibi

et al. 2018

The Annals of Thoracic Surgery

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Objective Therapy for moderate ischemic mitral regurgitation (IMR) remains unclear. Determination of myocardial viability, a necessary pre-requisite for an improvement in regional contractility, is a likely key factor in determining response to revascularization alone. Myocardial strain has been proposed as a viability measure but has not been compared to late gadolinium enhancement (LGE) cardiac (c)MRI. We hypothesized that abnormal strain overestimates non-viable LV segments measured using LGE and that ischemia and mechanical tethering by adjacent transmural myocardial infarction (TMI) also decreases strain in viable segments. Methods Sixteen patients with ≥ mild IMR and seven healthy volunteers underwent cMRI with non-invasive tags (CSPAMM), LGE and stress perfusion. CSPAMM images were post-processed with HARP and circumferential and longitudinal strains were calculated. Viability was defined as the absence of TMI on LGE (hyperenhancement >50% of wall thickness). The borderzone was defined as any segment bordering TMI. Abnormal strain thresholds (±1–2.5 SD from normal mean) were compared to TMI, ischemia and borderzone. Results 7.4% of LV segments had TMI on LGE while >14.5% of LV segments were non-viable by strain thresholds (p<0.005). In viable segments, ischemia impaired longitudinal strain (least perfused 1/3 of LV segments −.18±.08 vs. most perfused −.22±.1 p=01) and circumferential strain (−.12±.1 vs−.16±.08 p<0.05). In addition, infarct proximity impaired longitudinal strain (−.16±.11 borderzone vs −.18±.09 remote p=.05). Conclusions Impaired LV strain overestimates non-viable myocardium when compared to TMI on LGE. Ischemia and infarct proximity also decrease strain in viable segments.

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Magnetic resonance measurement of transient shear wave propagation in a viscoelastic gel cylinder

Cited by 34 publications

References 18 publications

Improved measurement of brain deformation during mild head acceleration using a novel tagged MRI sequence

Improved measurement of brain deformation during mild head acceleration using a novel tagged MRI sequence

Deformation of the human brain induced by mild angular head acceleration

Ischemic Mitral Regurgitation: Abnormal Strain Overestimates Nonviable Myocardium

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