0

Full Content is available to subscribers

Subscribe/Learn More  >

Brain Response to Extracranial Acoustic Loads: Shear Wave Propagation Characterized by Vector Fields

[+] Author Affiliations
Erik H. Clayton, Philip V. Bayly

Washington University in St. Louis, St. Louis, MO

Paper No. IMECE2011-63245, pp. 25-29; 5 pages
doi:10.1115/IMECE2011-63245
From:
  • ASME 2011 International Mechanical Engineering Congress and Exposition
  • Volume 2: Biomedical and Biotechnology Engineering; Nanoengineering for Medicine and Biology
  • Denver, Colorado, USA, November 11–17, 2011
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-5488-4
  • Copyright © 2011 by ASME

abstract

Traumatic brain injuries (TBI) due to blast are common in modern combat situations, and often lead to permanent cognitive impairment. Despite the prevalence and severity of blast-induced TBI, the condition remains poorly understood. Computer simulations of blast and blast injury mechanics offer enormous potential; however, computer models require accurate descriptions of tissue mechanics and boundary conditions in vivo. To gain insight into the mechanisms of blast injury, we applied direct (light) oscillatory pressure loading to the skulls of human volunteers, and measured displacement and strain fields using the methodology of magnetic resonance elastography (MRE). MRE is a non-invasive imaging modality that provides quantitative spatial maps of tissue stiffness. MRE is performed by inducing micron-amplitude propagating shear waves into tissue and imaging the resulting harmonic motion with standard clinical MRI hardware. Shear waves are initiated by an MR-compatible actuator and detected by a specialized “motion-sensitive” MRI pulse sequence (software). Motion sensitized MR images provide displacement field data which can be inverted to estimate material stiffness by invoking a restricted form of Navier’s equation. Clinical interest in MRE has largely been driven by the empirical relationship between tissue stiffness and health. However, the “raw” MRE data (3-D displacement measurements) themselves can elucidate loading paths, anatomic boundaries and the dynamic response of the intact human head. In this study, we use the MRE imaging technique to measure in vivo displacement fields of brain motion as the cranium is exposed to acoustic frequency pressure excitation (45, 60, 80 Hz) and we calculate the resulting shear-strain fields (2-D). We estimate the Poynting vector (energy flux) field to illuminate the directions of internal wave propagation, and to identify the energy absorbing and reflecting regions within the brain.

Copyright © 2011 by ASME

Figures

Tables

Interactive Graphics

Video

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In