1 / 50

In Vivo Measurement of Brain Biomechanics

In Vivo Measurement of Brain Biomechanics. PV Bayly, E Christoforou, C Kessens, SM Atay, A Sabet, GM Genin Washington University Mechanical and Aerospace Engineering. Motivation: Understanding TBI. What are forces on and accelerations of the skull?

yates
Download Presentation

In Vivo Measurement of Brain Biomechanics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. In Vivo Measurement of Brain Biomechanics PV Bayly, E Christoforou, C Kessens, SM Atay, A Sabet, GM Genin Washington University Mechanical and Aerospace Engineering

  2. Motivation: Understanding TBI • What are forces on and accelerations of the skull? • How does the brain deform in response to skull loading? • How does brain tissue respond to deformation?

  3. Example mild impact

  4. Soccer heading characterization Ball speed: 12m/s

  5. Understanding TBI • What are forces on and accelerations of the skull? • How does the brain deform in response to skull loading? • How does brain tissue respond to deformation?

  6. Measuring brain deformation • Tagged MR imaging • Gated image acquisition • Repeated motion • Analysis of displacement and strain

  7. Analysis: Track centers of tag lines Algorithm: Automatically identify intersections of harmonic phase contours (HARP)

  8. Analysis: Construct mesh from intersection points Deformed Reference

  9. [X1,Y1] [X3,Y3] [x1,y1] [x3,y3] DX3 dx3 DX1 dx1 DX2 dx2 [X2,Y2] [x2,y2] Analysis: Estimate Lagrangian strain in deformed mesh

  10. Example: simple shear

  11. Validation: gel phantom

  12. Methods: Angular acceleration Subject in scanner Gelatin phantom

  13. Rotational motion constraint Weight Latch Head Coil Head Cylinder

  14. MR imaging protocol

  15. Validation in gel phantom Experiment Simulation

  16. Analysis of deformation Cartesian (x,y) strain components Polar (r,θ) strain components

  17. Validation in gel phantom Simulation Experiment First peak: Maximum shear

  18. Validation in gel phantom Simulation Experiment Rebound: Minimum shear

  19. Comparison of experiment to simulation

  20. Acceleration-induced deformation of the human brain

  21. Methods: Controlled head motion Siemens Sonata 1.5T

  22. Methods: Repeated acceleration Acceleration: blue - Peak: 20-30 m/s2 - Duration: ~40 ms. Optical signal: green Imaging time: red

  23. Methods: Imaging planes

  24. Results: Acceleration-induced deformation of human brain

  25. Results: Acceleration-induced deformation of human brain

  26. Results: Acceleration-induced deformation of human brain

  27. Results: Acceleration-induced deformation of human brain

  28. HARP contours: Reference and deformed

  29. Results: Displacement Sagittal: Deformation scaled 5X

  30. Results: Displacement Transverse: Deformation scaled 5X

  31. Horizontal Positive (red): extension Negative (blue): shortening Vertical ( - ) Shear ( + ) Max. principal Results: Strain – sagittal plane Horizontal, vertical strains Shear strain

  32. Positive (red): extension Negative (blue): shortening Horizontal Vertical ( - ) ( + ) Shear Max. principal Results: Strain – transverse plane Horizontal, vertical strains Shear strain

  33. Positive (red): extension Negative (blue): shortening Results: Strain – Transverse plane Horizontal, vertical strains Horiz. Bungee jumping analogy Vert. Shear Brain suspension appears important

  34. Discussion • Measurement of brain deformation is feasible even during short, fast, linear accelerations. • Strains of 3-5% occur during 2-3 G accelerations • Brain “suspension” is important • This data will be valuable in developing accurate, validated computer models

  35. Brain deformation during angular acceleration of skull: MR methods • Head constrained to rotate • Volunteer initiates each acceleration event

  36. Results: Angular acceleration-induced deformation of human brain Subject 1: Plane 0 cm

  37. Results: Angular acceleration-induced deformation of human brain Subject 1: Plane +2 cm

  38. Results: Angular acceleration-induced deformation of human brain Subject 1: Plane -2 cm

  39. Results: Angular acceleration-induced deformation of human brain Subject 3: Plane 0 cm

  40. Results: Angular acceleration-induced deformation of human brain Subject 3: Plane +2 cm

  41. Analysis sequence Cartesian (x,y) strain components Polar (r,θ) strain components

  42. Results Radial-circumferential shear strain: εrθ

  43. Conclusions • MR methods can be used to estimate strain during fast angular accelerations • Strains: ~5% occur at 250-300 rad/s2 • Boundary conditions: Dura mater, falx, and tentoriummembranes, vessels, bony prominences are all important. • These data will be useful for development of accurate, validated computer models. Dura mater membrane Medial longitudinal fissure Tentorium membrane

  44. Future work: MR Elastography • MR visualization of shear waves • Shear modulus estimated from propagation speed 800 hz 1200 hz

  45. Future work: Tagged MRI • Higher temporal resolution • MR techniques • Higher accelerations • Animal studies • More types of head motion

  46. Acknowledgments G.M. Genin – Co-PI E. Leuthardt J. Ackerman K. Dikranian R.J. Okamoto X. Yu S.-K. Song E. Christoforou WU Human Performance Lab WU Small Animal Imaging Resource Southern Consortium on Injury Biomechanics Students: G. Meyer T. Cohen P. Massouros S. Ji A. Sabet C. Kessens

  47. Soccer heading: Raw acceleration data

  48.  Are heading impacts dangerous? • Angular acceleration, velocity << injury criteria1 • Sub-concussive • Effects of repeated impacts unknown. 1Margulies and Thibault (1992)

  49. How much deformation occurs? When? Area fraction: Fraction of image in which strain exceeds the specified level λ. Sagittal plane

  50. When are impacts dangerous? • Viscoelastic material responds to angular acceleration of outer boundary

More Related