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Traumatic Brain Injury at Cellular Level by Using Multi-scale Modelling in Comparison with Clinical Data

Hoursan, Hesam | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52824 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam; Ahmadian, Mohammad Taghi
  7. Abstract:
  8. This study aims to provide a multiscale model of traumatic brain injury including the three levels of macro, meso, and microscale information. In order to do this, a macroscale voxel-baed model of human head was constructed. The model was designed and generated to include mesoscale tissue information as well as a voxel-based approach to include voxel-based microscale data and to be coupled in a multiscale framework. Next, three different microscale models were constructed. The variations of fractional anisotropy within one standard deviation in the regions (including 60% to 70% of voxels) can change the stiffness of the tissue by up to the considerable amount of 40%. The microscale models attempted to include anisotropy and heterogeneity of the white matter tissue, consisting of the axonal fibers and the extra-cellular matrix in a representativevolume element. Heterogeneity within the white matter tissue was studies by including statistical data of fractional anisotropy from diffusion tensor imaging into the microscale hyperelastic Holzapfel model. Periodic boundary conditions were maintained in all microscale composite models to ensure the continuity and symmetry of deformations, stress, and strain in the RVEs. The last microscale model proposed included the histology information as well as DTI data to form a stochastic volume element which was also able to predict the tissue behaviour in both meso and micro scales. The results denote that the statistical volume element can predict the homogeneous and local tissue response to external stimula. The results indicated that the statistical model predicts the local stresses to be 2 and 3 times those of the symmetrical model under tension and shear, respectively. In addition, the current model is able to predict the tissue behaviour under shear deformations unlike the previously published models. Finally, a comprehensive multiscale model at the head level is formed and validated against the existing HIC data of diffuse axonal injury in three important sub-regions of the white matter
  9. Keywords:
  10. Finite Element Model ; Anisotropy ; Heteroscedasticity ; Micromechanical Model ; Traumatic Brain Injury (TBI)

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