ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

TOWARDS DETERMINING MECHANICAL PROPERTIES OF THE
BRAIN-SKULL INTERFACE: A STUDY USING BRAIN INDENTATION
EXPERIMENT AND MODELLING
M. Mazumder 1 , A. Wittek 1 , A. Mostayed 1 , G.R. Joldes 1 , S. M. Bunt 2 ,
R. Day 3 , R. Hart 4 and K. Miller 1
1. ABSTRACT
Knowledge of the mechanical properties of the brain-skull interface is important for
surgery simulation and injury biomechanics. However, very little is known about these
properties. This paper reports the experimental results from in-situ indentation of the
sheep brain near the brain–skull interface and suggests the mechanical properties for the
interface through complementing analysis of the results of these experiments with brain
modelling and computer simulation using non-linear finite element (FE) procedures.
2. INTRODUCTION
Information about the constitutive properties and boundary conditions of the analysed
continuum are key elements required for formulating mathematical models of physical
problems (Bathe, 1996). The mechanical properties of brain tissue have been
investigated for over four decades (Estes and McElhaney, 1970; Miller and Chinzei,
1997, 2002; Prange and Margulies, 2000; Bilston et al., 1997, 2001; Velardi et al.,
2006). However, knowledge of the mechanical properties of the brain-skull interface
that determines the boundary conditions for the brain is very limited (Jin 2009).
Consequently, the brain-skull interface models used in the literature are “best guesses”
and their relation to reality is unclear (Miller, 2011). In the literature, the brain-skull
interface has been modelled as either a tied, frictionless or frictional sliding contact,
with or without brain-skull separation (Hu et al., 2007; Ji et al., 2004; Ji and Margulies,
2007; Miga et al., 2000; Wittek et al., 2003, 2005, 2007). The most straightforward way
to determine the mechanical properties of the brain-skull interface would be to conduct
experiments on interface samples. However, the exact anatomical structure of this
interface is still a hotly debated topic, which is partly related to difficulties in extracting
the interface samples without damaging tissues that form the interface (Haines et al.,
1993). Therefore, in this study we conduct in-situ indentation of the sheep brain, and
propose to derive the macroscopic mechanical properties of the brain- skull interface
from the results of these experiments. To the best of our knowledge, this is the first ever
analysis of this kind. When conducting in-situ indentation of the brain, the reaction
force on the indentor was measured. After the indentation, nominally cylindrical
1 Intelligent Systems for Medicine Laboratory, The University of Western Australia, Australia.
2 School of Anatomy, Physiology and Human Biology, The University of Western Australia, Australia.
3 Department of Medical Physics, Royal Perth Hospital, Perth, Australia.
4 Department of Radiology, Royal Perth Hospital, Perth, Australia.