Computational Study of the Contribution of the Vasculature on the Dynamic Response of the Brain

Are in vivo and in situ brain tissues mechanically similar?

“…The present study characterized the intact brain organ, including the intact vascular tree, and the long-term shear moduli for porcine gray matter were on the same order (100's of Pa) as those obtained previously from in vitro specimens without large vessels (Prange and Margulies, 2002). We therefore conclude that the present experimental data do not support the theoretical hypothesis of Zhang et al (2002). Because the stiffness determined for brain tissue in FE models may dramatically affect the conclusions regarding injury criteria (e.g., see Table A2 in Klinich et al, 2002, summarizing a parametric FE study of brain deformations during impacts caused by motor-vehicle crashes), it is critical to validate the effective stiffness of brain material in FE studies with respect to effective stiffness of fresh brain tissue (Kleiven and Hardy, 2002).…”

“…The walls of the cerebral blood vessels, with elastic moduli in the range of 1-10 MPa (Monson et al, 2000), are stiffer than brain parenchyma by several orders of magnitude. Accordingly, the 2D simulations of Zhang et al (2002) demonstrated that vessel walls, rather than the perfusion pressure, may be the significant vascular contributor to the brain's mechanical stiffness and strength. However, their idealization of the 3D vascular tree as a 2D structure composed of straight beams could have introduced artificial stiffening of the brain-vasculature composite.…”

“…We cannot discount the possibility that tissue regions with higher local CBV fractions might have significant differences between in vivo and in situ conditions. Another recent paper, by Zhang et al (2002), addressed the question whether the vascular tree of the brain should be explicitly included in FE simulations of TBI. The walls of the cerebral blood vessels, with elastic moduli in the range of 1-10 MPa (Monson et al, 2000), are stiffer than brain parenchyma by several orders of magnitude.…”

Dynamic response of the brain with vasculature: A three-dimensional computational study

“…As blood vessels are more rigid than cerebral tissue (Chalupnik et al, 1971;Lo¨wenhielm, 1974;Lee and Haut, 1989;Monson, 2001), they are likely to stiffen the structural responses of the brain. Previous studies have been conducted to investigate the structural influence of the vasculature (Omori et al, 2000;Zhang et al, 2002;Parnaik et al, 2004) and the results have been contradictory.…”

Significance of source and size in the mechanical response of human cerebral blood vessels

“…Cerebral blood vessels are damaged in 94% of all fatalities associated with head trauma (Graham, 1996). These vessels additionally form part of the composite structure of the brain and, because of their relative stiffness in comparison to brain tissue, play an important role in the overall response of the brain to loading (Zhang et al, 2002). Nevertheless, computational models of traumatic brain injury do not yet account for the vasculature, in part because detailed mechanical properties of this tissue have not been available (Bandak and Eppinger, 1994;Vossoughi and Bandak, 1996).…”