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Research Papers

Simulation of Blast-Induced Early-Time Intracranial Wave Physics leading to Traumatic Brain Injury

[+] Author and Article Information
Paul A. Taylor

Department of Penetration Systems, Sandia National Laboratories, Albuquerque, NM 87185

Corey C. Ford

Department of Neurology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-0001

J Biomech Eng 131(6), 061007 (Apr 27, 2009) (11 pages) doi:10.1115/1.3118765 History: Received February 11, 2008; Revised February 26, 2009; Published April 27, 2009

The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1mm3 voxels) five material model of the human head was created by segmentation of color cryosections from the Visible Human Female data set. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH , and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior, and lateral directions. Three-dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric stress within the first 2 ms of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 ms time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early-time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Head model. Color code: red=bone, light blue=white matter, dark blue=gray matter, and yellow=cerebral spinal fluid. Voxel resolution: 1 mm3.

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Figure 2

Compression curve describing the volumetric response for dry air, generated from the tabular equation-of-state model representing the air surrounding the head and occupying sinuses

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Figure 3

Wave form of approximated air blast structure of 1.3 MPa (13 bars) magnitude

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Figure 4

Midsagittal view of 1.3 MPa frontal blast scenario at various times. Plots are external and intracranial pressure distributions. Color scale: blue=0.11 MPa and red=5 MPa.

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Figure 5

Maximum pressure (row A) and volumetric tension (row B) in a midventricular axial plane for anterior, posterior, and right lateral blast orientations, where red indicates the highest values and blue the lowest. Note that tension values are negative relative to pressure. Scale: Row A: blue=1 KPa, red=6 MPa; and Row B: blue=1 KPa, red=1.2 MPa. The horizontal dashed lines in the upper left figure indicate the location of the coronal planes shown in Fig. 7.

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Figure 6

Maximum pressure (row A) and volumetric tension (row B) in a midsagittal plane for anterior, posterior, and right lateral blast orientations, where red indicates the highest values and blue the lowest. Note that tension values are negative relative to pressure. Scale: Row A: blue=1 KPa, red=6 MPa; and Row B: blue=1 KPa, red=0.9 MPa. The dashed line in the upper left figure indicates the location of the axial images shown in Fig. 8, row A.

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Figure 7

Maximum deviatoric stress in representative coronal planes for anterior, posterior, and right lateral blast orientations. Scale: (all rows): blue=0.1 KPa, red=15 KPa. Rows A–D correspond to the horizontal dashed lines appearing in the upper left axial image of Fig. 5. Arrows indicate regions of focal or diffusely elevated shear stress discussed in the text.

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Figure 8

Maximum deviatoric (shear) stress in a midventricular axial plane (row A) and midsagittal plane (row B) for anterior, posterior, and right lateral blast orientations. Scale: Row A: blue=0.1 KPa, red=15 KPa; and Row B: blue=0.1 KPa, red=25 KPa. Arrows and ovals indicate regions of focal or diffusely elevated shear stress discussed in the text.

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Figure 9

Tracer point examples in an axial slice below the lateral ventricles, passing through frontal and temporal lobes. The axial position of this slice is identified by the horizontal dashed line in the upper left image of Fig. 6. Red=skull bone, dark blue=gray matter, light blue=white matter, and yellow=cerebral spinal fluid.

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Figure 10

Pressure (left) and deviatoric stress (right) at tracer locations 64 and 65 located in the frontal lobes of the axial slice in Fig. 9. The deviatoric stress plots are equivalent to von Mises stress.

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Figure 11

Pressure (left) and deviatoric stress (right) at tracer locations 66 and 67 located in the temporal lobes of the axial slice in Fig. 9. The deviatoric stress plots are equivalent to von Mises stress.

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