This study demonstrates a novel model generation methodology that addresses several limitations of conventional finite element head models. By operating chiefly in imagespace, new structures can be incorporated or merged, and the mesh either decimated or refined both locally and globally. This methodology is employed in the development of a highly bio-fidelic finite element head model from high resolution scan data. The model is adaptable and presented here in a form optimised for impact and blast (Schneiderman et al. 2008). Considerable research has been devoted to investigating the mechanisms which generate TBI in cases where the head is subjected to impact or blast. Of the various experimental methods available (in vivo human experiments, or tests on cadaveric, animal, physical, or mathematical models) the increasing availability of computing power has seen numerical simulation, and in particular the finite element (FE) method, come to the forefront of this research. The current study details the development of a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Finite element modellingFE simulation is an invaluable tool in the exploration of complex trauma mechanisms resulting from dynamic insults such as impacts and blasts. While sophisticated FE models of the head offer the prospect of providing accurate and repeatable experimental analyses of all categories of mechanical head injury, the validity of these models is heavily influenced by the geometric accuracy of the structures within the model. Traditionally computational models are created manually using computer aided design (CAD) tools, but when concerned with the complex anatomy of the head and its internal structures this manual approach has significant disadvantages; there is a large scope for subjectivity and user error, as well as of becoming rapidly computationally intractable as more geometric fidelity is introduced. A novel model generation approach which can reduce the inaccuracies associated with modelling a highly complex structure is known as 'image based meshing'. This refers to the conversion of volume scan data, generally from computed tomography (CT) or magnetic resonance imaging (MRI), directly into an FE mesh by way of fully-and semi-automated processes with minimal user input. This increases not only the accuracy, but also the speed at which computational models of complex geometries can be constructed, thereby allowing a greater number of anatomical features to be distinguished.In 1997, Mehta et al. selected 14 cross-sectional image 'slices' from an MRI scan of the head and highlighted the skull in these images using an image processing tool. These highlighted outlines of the bone could then be read by a C++ computer code and converted into CAD coordinate and spline data, from which a model could be constructed that was, at least partially, based on the ...

When the head is subject to non-penetrating (blunt) impact, contusion-type injuries are commonly identified beneath the impact site (the coup) and, in some instances, at the opposite pole (the contre-coup). This pattern of injury has long eluded satisfactory explanation and blunt head injury mechanisms in general remain poorly understood. There are only a small number of studies in the open literature investigating the head's response to short duration impacts, which can occur in collisions with light projectiles. As such, the head impact literature to date has focussed almost exclusively on impact scenarios which lead to a quasi-static pressure response in the brain. In order to investigate the response of the head to a wide range of impact durations, parametric numerical studies were performed on a highly bio-fidelic finite element model of the human head created from in vivo magnetic resonance imaging (MRI) scan data with non-linear tissue material properties. We demonstrate that short duration head impacts can lead to potentially deleterious transients of positive and negative intra-cranial pressure over an order of magnitude larger than those observed in the quasi-static regime despite reduced impact force and energy. The onset of this phenomenon is shown to be effectively predicted by the ratio of impact duration to the period of oscillation of the first ovalling mode of the system. These findings point to dramatically different pressure distributions in the brain and hence different patterns of injury depending on projectile mass, and provide a potential explanation for dual coup/contre-coup injuries observed clinically.

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A new approach to generating physical and numerical models of the human head is presented. In this study, analytical, numerical and experimental models were used in parallel to explore the pressure response of the human head as a result of low velocity impact.