90
L. E. Bilston
methods) and large deformation measurements (e.g. by indentation, aspiration, or
other methods), are needed.
Brain mechanics at high loading rates still requires more study, including
separating out tissue inertial effects from inherent tissue viscoelasticity. At low
loading rates, high-quality quantitative data on interstitial fluid flow in the brain,
as is thought to be relevant for diseases such as hydrocephalus, is still lacking.
The use of easily interpretable constitutive models may also assist the field of
brain tissue mechanics. While some mechanical properties have intrinsic definitions
that are interpretable without reference to a constitutive model, such as the linear
viscoelastic moduli, other parameters that are widely reported, often incorrectly, to
describe tissue properties beyond this linear range are parameters within constitutive
models, with their own inherent assumptions. Given the complexity and strong
nonlinearity of brain tissue mechanical response, it is unrealistic to expect that one
constitutive model will fit all circumstances, and those who wish to describe brain
tissue properties in a given context will need to select and use a model that can
capture the features of brain tissue mechanics within the relevant loading regime. A
model that works for quasistatic brain deformation during surgery will likely not be
suitable for high-velocity impact loading, for example.
4.8 Conclusions
While interest in brain tissue mechanics is enjoying a resurgence of late, and much
data has been collected to characterise the response of brain tissue to mechanical
loading, there is still much to be done to rigorously characterise this complex
material. New developments in measuring techniques, including MRE, however,
have great potential for noninvasively measuring tissue properties in vivo, which
may allow these properties to be used for diagnostic purposes, as well as shedding
light on how this complex organ responds to loads, be they due to dynamic processes
that lead to traumatic brain injury or slow processes involved in neurological
diseases such as brain tumours or hydrocephalus.
Acknowledgements Lynne Bilston is supported by an NHMRC Senior Research Fellowship.
References
1. Geng, G., Johnston, L.A., Yan, E., Britto, J.M., Smith, D.W., Walker, D.W., Egan, G.F.:
Biomechanisms for modelling cerebral cortical folding. Med. Image Anal. 13, 920–930 (2009)
2. McHedlishvili, G., Itkis, M., Sikharulidze, N.: Mechanical properties of brain tissue related to
oedema development in rabbits. Acta Neurochir. 96, 137–140 (1989)
3. Pang, D., Altschuler, E.: Low-pressure hydrocephalic state and viscoelastic alterations in the
brain. Neurosurgery. 35, 643–655; discussion 655–656 (1994)
L. E. Bilston
methods) and large deformation measurements (e.g. by indentation, aspiration, or
other methods), are needed.
Brain mechanics at high loading rates still requires more study, including
separating out tissue inertial effects from inherent tissue viscoelasticity. At low
loading rates, high-quality quantitative data on interstitial fluid flow in the brain,
as is thought to be relevant for diseases such as hydrocephalus, is still lacking.
The use of easily interpretable constitutive models may also assist the field of
brain tissue mechanics. While some mechanical properties have intrinsic definitions
that are interpretable without reference to a constitutive model, such as the linear
viscoelastic moduli, other parameters that are widely reported, often incorrectly, to
describe tissue properties beyond this linear range are parameters within constitutive
models, with their own inherent assumptions. Given the complexity and strong
nonlinearity of brain tissue mechanical response, it is unrealistic to expect that one
constitutive model will fit all circumstances, and those who wish to describe brain
tissue properties in a given context will need to select and use a model that can
capture the features of brain tissue mechanics within the relevant loading regime. A
model that works for quasistatic brain deformation during surgery will likely not be
suitable for high-velocity impact loading, for example.
4.8 Conclusions
While interest in brain tissue mechanics is enjoying a resurgence of late, and much
data has been collected to characterise the response of brain tissue to mechanical
loading, there is still much to be done to rigorously characterise this complex
material. New developments in measuring techniques, including MRE, however,
have great potential for noninvasively measuring tissue properties in vivo, which
may allow these properties to be used for diagnostic purposes, as well as shedding
light on how this complex organ responds to loads, be they due to dynamic processes
that lead to traumatic brain injury or slow processes involved in neurological
diseases such as brain tumours or hydrocephalus.
Acknowledgements Lynne Bilston is supported by an NHMRC Senior Research Fellowship.
References
1. Geng, G., Johnston, L.A., Yan, E., Britto, J.M., Smith, D.W., Walker, D.W., Egan, G.F.:
Biomechanisms for modelling cerebral cortical folding. Med. Image Anal. 13, 920–930 (2009)
2. McHedlishvili, G., Itkis, M., Sikharulidze, N.: Mechanical properties of brain tissue related to
oedema development in rabbits. Acta Neurochir. 96, 137–140 (1989)
3. Pang, D., Altschuler, E.: Low-pressure hydrocephalic state and viscoelastic alterations in the
brain. Neurosurgery. 35, 643–655; discussion 655–656 (1994)