Assessment of in vivo and post-mortem mechanical behavior of brain tissue using magnetic resonance elastography

Vappou, Jonathan; Breton, Élodie; Choquet, Philippe; Willinger, Rémy; Constantinesco, A.

doi:10.1016/j.jbiomech.2008.07.034

Cited by 67 publications

(47 citation statements)

References 16 publications

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“…Examining the spectral content of the shear waves generated by both transducers ( Figure 5 ) and confirming a consistent, narrow band frequency distribution was important because a change in shear wave bandwidth can lead to slight changes in shear wave group velocity. For the associated shear wave frequency range of 200-500 Hz, shear modulus values from our SWEI data match several subsets of published in vivo and in vitro results (Arbogast and Margulies, 1997; Thibault and Margulies, 1998; Vappou et al, 2008). …”

Section: Discussionsupporting

confidence: 83%

Material Characterization of in Vivo and in Vitro Porcine Brain Using Shear Wave Elasticity

Urbanczyk

Palmeri

Bass

2015

Ultrasound in Medicine & Biology

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Realistic computer simulation of closed head trauma requires accurate mechanical properties of brain tissue, ideally in vivo. A substantive deficiency of most existing experimental brain data is that properties were identified through in vitro mechanical testing. This study develops a novel application of shear wave elasticity imaging (SWEI) to assess porcine brain tissue shear modulus in vivo. SWEI is a quantitative ultrasound technique that has been used here to examine changes in brain tissue shear modulus as a function of several experimental and physiological parameters. Animal studies were performed using two different ultrasound transducers to explore the differences between physical response with closed skull and open skull arrangements. In vivo intracranial pressure (ICP) in four animal subjects was varied over a relevant physiological range (2-40 mmHg), and was correlated with shear wave speed and stiffness estimates in brain tissue. We found that stiffness does not vary with modulation of ICP. Additional in vitro porcine specimens (n=14) were used to investigate variation in brain tissue stiffness with temperature, confinement, spatial location, and transducer orientation. We found a statistically significant decrease in stiffness with increased temperature (23%) and an increase in stiffness with decreasing external confinement (22 - 37%). This study demonstrated the feasibility of using SWEI to characterize porcine brain tissue both in vitro and in vivo. Our results underline the importance of temperature and skull derived boundary conditions on brain stiffness and suggests that physiological ranges of ICP do not significantly affect in situ brain tissue properties. SWEI allowed for brain material properties to be experimentally-characterized in a physiological setting and provides a stronger basis for assessing brain injury in computational models.

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Section: Discussionsupporting

confidence: 83%

Material Characterization of in Vivo and in Vitro Porcine Brain Using Shear Wave Elasticity

Urbanczyk

Palmeri

Bass

2015

Ultrasound in Medicine & Biology

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“…Several of these mechanisms are related to the complex shear modulus of the brain. Only recently has noninvasive imaging of the complex shear modulus in the brain been possible (17)(18)(19)(20)(21). This study is the first to assess alterations in the viscoelastic properties of brain tissue in NPH.…”

Section: Discussionmentioning

confidence: 96%

In vivo viscoelastic properties of the brain in normal pressure hydrocephalus

et al. 2010

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Nearly half a century after the first report of normal pressure hydrocephalus (NPH), the pathophysiological cause of the disease still remains unclear. Several theories about the cause and development of NPH emphasize disease-related alterations of the mechanical properties of the brain. MR elastography (MRE) uniquely allows the measurement of viscoelastic constants of the living brain without intervention. In this study, 20 patients (mean age, 69.1 years; nine men, 11 women) with idiopathic (n = 15) and secondary (n = 5) NPH were examined by cerebral multifrequency MRE and compared with 25 healthy volunteers (mean age, 62.1 years; 10 men, 15 women). Viscoelastic constants related to the stiffness (µ) and micromechanical connectivity (α) of brain tissue were derived from the dynamics of storage and loss moduli within the experimentally achieved frequency range of 25-62.5 Hz. In patients with NPH, both storage and loss moduli decreased, corresponding to a softening of brain tissue of about 20% compared with healthy volunteers (p < 0.001). This loss of rigidity was accompanied by a decreasing α parameter (9%, p < 0.001), indicating an alteration in the microstructural connectivity of brain tissue during NPH. This disease-related decrease in viscoelastic constants was even more pronounced in the periventricular region of the brain. The results demonstrate distinct tissue degradation associated with NPH. Further studies are required to investigate the source of mechanical tissue damage as a potential cause of NPH-related ventricular expansions and clinical symptoms.

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“…Experiments on physical models of brain injury have been performed using gel-filled skulls, e.g., (Margulies et al, 1990; Meaney et al, 1995), and high-speed biplanar x-ray measurement of radio-opaque targets embedded in cadaver brains during skull impact (Hardy et al, 2001). However, these physical models provide only a sparse set of data points and lack many of the features of the living brain (Gefen and Margulies, 2004; Vappou et al, 2008). …”

Section: Introductionmentioning

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

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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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Assessment of in vivo and post-mortem mechanical behavior of brain tissue using magnetic resonance elastography

Cited by 67 publications

References 16 publications

Material Characterization of in Vivo and in Vitro Porcine Brain Using Shear Wave Elasticity

Material Characterization of in Vivo and in Vitro Porcine Brain Using Shear Wave Elasticity

In vivo viscoelastic properties of the brain in normal pressure hydrocephalus

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

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