Understanding brain injury mechanism: integrating real world lesions, ATD response and finite element modeling

Transcription

1 Understanding brain injury mechanism: integrating real world lesions, ATD response and finite element modeling Jillian E. Urban, Sarah Lynch, Christopher T. Whitlow, Joseph Maldjian, Alexander Powers, Wayne Meredith, Warren Hardy, Erik Takhounts, Joel D. Stitzel CIREN Public Meeting September 2012 Center for Injury Biomechanics C I B COLLEGE of ENGINEERING

2 WFU CIREN Brain Project Team Medical Personnel Chris Whitlow Neuroradiology Alex Powers Neurosurgery Joseph Maldjian Neuroradiology Engineers Jillian Urban Biomechanics Joel D. Stitzel Biomechanics 2012 Summer Students Year 1 Support Landon Edwards Neuroradiology Fellow Colston Edgerton Medical Student Kavya Reddy Medical Student Pavani Thotakura Medical Student Rachel Austin Wayne Meredith Summer Student General Surgery Sarah Lynch Carly Sombric Andrew Chambers Summer Student

3 Brain Injury ~1.7 million people sustain a TBI each year TBI from MVCs are a leading cause for hospitalization Head injuries are leading cause of fatalities for frontal crashes in NASS CDS Yoganandan et al Head contact loading and resulting injury/fatality using CIREN Witt et al Utilized image segmentation of CT to identify age and gender volume differences in subdural hematoma after MVC

4 Biomechanics Paradigm Outside Vehicle Crash Reconstruction Crash Characteristics Inside Vehicle Belt Use Involved Physical Component Airbag Deployment Outside Occupant Scalp Contusion Injury Causation Scenario Internal Injury Intracranial Lesion Glasgow Coma Scale Injury Severity Score

5 The SIMon Computer Model: Simulated Injury Monitor FEM Created by NHTSA Works in conjunction with acceleration data from ATDs Simplified model for faster computation Takhounts et al, 2008

6 Introduction NAP data from dummy is converted to 6 load curves to drive the rigid body head model Crash Test NAP Data Load Curves

7 This is what SIMon does: Introduction

8 Medical Imaging Collect Soft Tissue CT and CIREN Database Information for all Brain Injuries Volumetric Analysis: Segment Brain Injuries Analyze Extent and Distribution of Brain Injury Determine Head Kinematics from ATD using NHTSA Crash Test Database Identify Contact: Soft Tissue Scalp Contusion Finite Element Modeling Create Corridors Describing Resultant Head Motion for Contact within Vehicle Parameterize Head Impact and Calculate Head Motion Apply to SIMon Analyze Extent and Distribution of Strain

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10 Recall Year 1: Collect volume of brain injury from CIREN database Number of Good Scans Number of Coded Intracranial Injuries (excluding Fractures) Number of Top 10 Intracranial Injuries Distribution of Top 10 Injury Codes

11 Identifying and Masking Specific Injuries Identified injured brain tissue based on Radiology Report description and common injury identifiers Subarachnoid Hemorrhage (SAH) Subdural Hematoma (SDH) Epidural Hematoma (EDH) Cerebral Contusion or Intracerebral Hemorrhage Intraventricular Hemorrhage (IVH) Diffuse Axonal Injury (DAI) Pneumocephalus Segmented using a semi automated method of thresholding and dynamic region growing

12 Methods Volume of injury calculated from number of voxels and size of voxels within injury mask The point of contact between the head and vehicle was identified by the presence of a superficial soft tissue/scalp contusion on the CT images Simple linear regression used to correlate injury outcome to crash data SDH Volume

13 Identify Point of Contact: Soft Tissue Contusion R L If soft tissue swelling was not evident, point of contact on the head was identified from the involved physical component/injury causation scenario

14 Identify Lesion Location: Segmented Volume R L

15 This work has been accepted to Journal of Neurotrauma August 2012 Year 1 Recall: SDH Analysis Nearside Greatest Crash Velocity Most closely correlating variable with SDH volume is crash velocity (p=0.0659) Trending correlation between age and midline shift (p=0.0702) Frontal Greatest SDH volume Midline Shift was significantly positively correlated with maximum crush of the vehicle (p=0.0190*) for all occupants Trending correlation between age and SDH Volume (p=0.0599)

16 CIREN Brain Proposal Goal Quantify subdural hematoma (SDH), subarachnoid hemorrhage (SAH), and unilateral contusion Investigate similar crash tests to real world cases Apply parameterized variables of impact to SIMon Relate model response to real world injury response Input Condition from patient data Response of the model

17 Previous Work Brain tissue was sliced in the coronal plane Within the plane brain was sectioned Each section is marked 1 = damaged 0 = no damage Distribution noted as a percentage of injury by region Ryan et al, Brain Injury Patterns in Fatally Injured Pedestrians. The Journal of Trauma, April Gorrie et al, Fatal head injury in children: a new approach to scoring axonal and vascular damage. Childs Nervous System, July 1999.

18 Previous Work Tagliaferri et al.: those occupants with higher BMI are more likely to sustain a severe head injury following a frontal crash Mallory et al, Richmond et al., Stitzel et al., Severity and mortality of head injury is age dependent Mallory, Head Injury and Aging: The Importance of Bleeding Injuries, Annals of Advances in Automotive Medicine, 2010 Delta v and maximum crush have been found to be reliable predictors of injury severity in individuals with head trauma

19 Previous Work Yoganandan et al. and Nirula et al.: direct contact loading results in a high percentage of occupants with brain injury Pillars and side rail Yoganandan et al. Severe to Fatal Head Injuries, Accident Analysis and Prevention, 2010 Morris et al.: ¼ of severe head injuries occur due to contact within the vehicle are diffuse in nature

20 CIREN Brain Project Work Flow Quantify Extent and Distribution of Injury SAH SDH Contusion Collect Parameters for Impact Corridors NHTSA Crash Database ATD Head Motion Parameterize Define Impact Vector Calculate Resulting Head Motion Compare Extent and Distribution of Strain to that of Injury Finite Element Modeling: SIMon Y X

21 Quantify Extent and Distribution of Injury Common brain coordinate system established from bony landmarks on the skull Nasion Right & Left External Auditory Meatus (EAM) Translate and rotate local subject axis to global axis Nasion Nasion EAM Left EAM

22 Quantify Extent and Distribution of Injury Spherical Coordinate System Delaunay triangulation used for volume calculation at 0.2 radial increments of azimuth and elevation Optimize volume calculation

23 R L Subdural Hematoma 0.2 radians x 0.2 radians Contact Location Injury A

24 Volume Distribution: Subdural Hematoma 6000 Posterior R 0 Volume (mm 3 ) Anterior _ Theta (Degrees)

25 Volume Distribution: Subdural Hematoma 6000 Posterior R 0 Volume (mm 3 ) Anterior _ Theta (Degrees)

26 Subarachnoid Hemorrhage Key 0.2 radians x 0.2 radians Increasing Volume

27 Quantify Extent and Distribution of Injury Future work: extend evaluation to the extent and distribution structurally using a brain atlas

29 Data Collection Database Search: NCAP: New Car Assessment Program IIHS: Insurance Institute for Highway Safety FMVSS: Federal Motor Vehicle Safety Standard Crash Test Parameters Crash Configuration Impacted Object ATD Type Nine Accelerometer Package Collect head motion from 9 Accelerometer Package Filtered at 1000 Hz X, Y, Z Translational Acceleration X, Y, Z Rotational Acceleration Calculate resultant linear and angular head motion Defined in the SIMon coordinate system

30 Group by contact type Verify contact type FRONT IMPACT: A Pillar, Steering Wheel (Wheel, Hub, Rim) SIDE IMPACT: B Pillar, Header, Other Vehicle Verify contact type with crash test photos/video

31 video

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33 Collect Raw Data: Angular and Translational Velocity (B Pillar) X Angular Velocity Y Angular Velocity Z Angular Velocity X Translational Velocity Y Translational Velocity Z Translational Velocity

34 Calculate Resultant Velocities (B Pillar) Identify Outliers

35 Resultant Curves for Corridor Calculation (B Pillar) Rotational Velocity (rad/s) Time (ms) (s)

36 Aligning Curves Y Characteristic Curve Y X 1 Y Maximum Value X X 20% of Maximum *20% of maximum was determined to be appropriate by Maltese et al.

37 Aligning Curves Y 1 Y X 26 Y 1 X X

38 Aligned Curves: B Pillar Angular Velocity (rad/s) Time (s)

39 Creating Corridors +STD 6 +STD 3 +STD 4 +STD 5 +STD 2 Velocity +STD 1 STD 4 STD 5 STD 6 STD 2 STD 3 STD 1 Time 1 Time 2 Time 3 Time 4 Time 5 Time 6

40 Creating Corridors Velocity Time 1 Time 2 Time 3 Time 4 Time 5 Time 6

41 B Pillar Angular Velocity (rad/s) Time (ms) Angular Velocity (rad/s) Time (s)

43 Parameterize Contact Location Location Magnitude Orientation GOAL: Parameterize a force vector defined in a local and global spherical coordinate system resulting translational and angular velocity Varied variables: Magnitude (5):Average, +/ 1 and 2 standard deviation Location (17) :Possible values along SD for location target Orientation

44 Kerrigan et al Pedestrian Head Impact Dynamics Magnitude (3) Gather time history of the components of the contact force (between the head and vehicle) Input: Neck loads Mass of the head Resulting linear acceleration components from the ATD Output: Magnitude of resultant force on head

45 Location Soft tissue swelling Injury Causation Scenario Involved Physical Component Contact location identified from soft tissue swelling Centroid of the swelling point cloud collected and determined the primary contact location Average contact location + 1 and 2 standard deviation calculated radially

46 Orientation All possible at +/ angle measures (0:15:90) Local Coordinate System defined tangent to sphere Local Coordinate System Global Coordinate System

47 Calculate Resulting Head Motion from Vector Newton Euler (NE) matrix Linear and angular impulse Distance from the CG Calculate the change in rotational and translational velocity over time d z d x Y X

48 Methods: Parameterize Vary all possible combinations of Magnitude, Location, and Orientation ~ 43,000 Compare calculated head motion (from velocity plots) to the ATD head motion corridors by contact type Biorank Sprague and Geers

49 Parameterized Results Magnitude: 0.5 Average Location: Theta: 105 o Phi: 0 o Orientation: Theta: 15 o Phi: 25 o Angular Velocity (rad/s) Resultant Angular Velocity (rad/s) X Angular Y Angular Z Angular

51 Preliminary Work: Example Comparison Case NCAP Toyota Rav kph Frontal Barrier Impact Test 12FDEW3 50 th % Male Dummy, Driver, Belted, Airbag CIREN Toyota Rav4 Frontal Impact, Delta V 56.0 kph 12FDEW4 Female Occupant, Driver, Belted, Airbag

52 Preliminary Work: Example Comparison Case Translational Velocity (m/s) X Y Z Time (s) 40 Rotational Velocity (rad/s) X -60 Y Z Time (s)

53 Preliminary Work: Example Comparison Case Corpus Callosum

54 Largest CSDM and Cerebrum SCSDM Isolated Z(-) rotation Total brain: CSDM(0.10)= 0.50 Cerebrum: SCSDM(0.10)= 0.50

55 Conclusion Quantified extent and distribution of SAH, SDH, cerebral contusion Collected parameters and generated corridors for b pillar and header contacts Calculated head motion from parameterized vector Future work: Continue to quantify injuries Input parameterized head motion to SIMon Final goal to integrate real world and computational modeling to better understand brain injury mechanisms and metrics to predict them

56 Acknowledgments C I B THANK YOU! National Highway Traffic Safety Administration CIREN Partner Centers WFU VT CIB Summer Interns: Sarah and Carly Work was performed for the Crash Injury Research and Engineering Network (CIREN) Project at Wake Forest University School of Medicine in cooperation with the United States Department of Transportation/National Highway Traffic Safety Administration (USDOT/NHTSA). Funding has been provided by the National Highway Traffic Safety Administration under Cooperative Agreement Number DTNH22 10 H Views expressed are those of the authors and do not represent the views of any of the sponsors or NHTSA. Wake Forest University School of Medicine CIREN Center