Biomechanical analysis of traumatic brain injury by MRI-based finite element modeling

Chen, Ying

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https://hdl.handle.net/2142/29640 Copy

Description

Title

Biomechanical analysis of traumatic brain injury by MRI-based finite element modeling

Author(s)

Chen, Ying

Issue Date

2012-02-06T20:08:16Z

Director of Research (if dissertation) or Advisor (if thesis)

Ostoja-Starzewski, Martin

Committee Member(s)

• Jasiuk, Iwona M.
• Hilton, Harry H.
• Gioia, Gustavo

Department of Study

Mechanical Sci & Engineering

Discipline

Theoretical & Applied Mechans

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• finite element modeling
• finite element mesh
• traumatic brain injury
• stress waves
• magnetic resonance imaging
• image processing

Abstract

The finite element (FE) modeling is a powerful tool for investigating the physical process producing head trauma, and a well validated model would, thus, be a valuable tool to aid in injury diagnosis and design of protective devices. Many FE head models with various degrees of simplification have been developed in the past several decades. There are, however, two common problems with the existing models. First, the mesh generation method is often time-consuming, and the generated mesh is unable to represent the important geometric characteristics of the complex human head. Second, existing models are validated using either intracranial pressure or deformation measured by cadaver experiments, but the extent to which the experimental results may be applied to live human brains is uncertain due to discrepancies between material properties of in vivo and cadaver brains. In the first part of this work, we develop a 3D FE head model that accounts for important geometric characteristics of the head using an efficient magnetic resonance imaging (MRI) voxel-based mesh generation method. The model is validated against intracranial pressures measured in a previous cadaver frontal impact experiment. The model is run under either of two extreme assumptions—free or fixed—concerning the head-neck junction, and the experimental measurements are well bounded by computed pressures from the two boundary conditions. The presence of a spherically convergent shear wave pattern in the brain is uncovered through our FE simulation, and that provides the first computational mechanics support for the centripetal hypothesis of cerebral concussion. It is concluded that the frontal impact gives rise not only to a fast pressure wave but also a slow and spherically convergent shear stress wave that is potentially more damaging to the brain tissue. In the second part of this work, we first study in vivo human brain deformation under mild impact induced by a 2-cm head drop using tagged MRI and the harmonic phase (HARP) imaging analysis technique originally developed for cardiac motion analysis. The FE simulation of mild impact is then carried out using the proposed 3D head model. The predicted deformation field from FE modeling correlates reasonably well with the results of MRI-based assessments. To our knowledge, this study is the first attempt in which the deformation field obtained by MRI-based assessment is correlated with the prediction of a corresponding FE model, and it is also the first validation of an FE brain injury model on in vivo human brain deformation data. It is found in this study that the maximum deformations occur within a few milliseconds following the impact, which is during the first oscillation of the brain within the skull, with maximum displacements of 2-3 mm and maximum strains of 5-10%.

Graduation Semester

2011-12

Permalink

http://hdl.handle.net/2142/29640

Copyright and License Information

Copyright 2011 Ying Chen

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