title: On the appropriateness of modelling brain parenchyma as a biphasic continuum.
abstract: Computational methods originally developed for analysis in engineering have been applied to the analysis of biological materials for many years. One particular application of these engineering tools is the brain, allowing researchers to predict the behaviour of brain tissue in various traumatic, surgical and medical scenarios. Typically two different approaches have been used to model deformation of brain tissue: single-phase models which treat the brain as a viscoelastic material, and biphasic models which treat the brain as a porous deformable medium through which liquid can move. In order to model the brain as a biphasic continuum, the hydraulic conductivity of the solid phase is required; there are many theoretical values for this conductivity in the literature, with variations of up to three orders of magnitude. We carried out a series of simple experiments using lamb and sheep brain tissue to establish the rate at which cerebrospinal fluid moves through the brain parenchyma. Mindful of possible variations in hydraulic conductivity with tissue deformation, our intention was to carry out our experiments on brain tissue subjected to minimal deformation. This has enabled us to compare the rate of flow with values predicted by some of the theoretical values of hydraulic conductivity from the literature. Our results indicate that the hydraulic conductivity of the brain parenchyma is consistent with the lowest theoretical published values. These extremely low hydraulic conductivities lead to such low rates of CSF flow through the brain tissue that in effect the material behaves as a single-phase deformable solid.
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: A C R
authors.initials: ACR
authors.lastname: Tavner
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: T Dutta
authors.initials: TD
authors.lastname: Roy
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: K W W
authors.initials: KWW
authors.lastname: Hor
authors.affiliation: School of Anatomy, Physiology and Human Biology, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Majimbi
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: G R
authors.initials: GR
authors.lastname: Joldes
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Wittek
authors.affiliation: School of Anatomy, Physiology and Human Biology, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Bunt
authors.affiliation: Intelligent Systems for Medicine Laboratory, School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia. Electronic address: karol.miller@uwa.edu.au.
authors.forename: K
authors.initials: K
authors.lastname: Miller
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001921:Brain / Q000502:physiology*; D008954:Models, Biological; D016062:Porosity; D012756:Sheep
keywords: Biphasic continuum; Brain; Consolidation theory; Mechanical properties