title: Viscoelasticity of subcortical gray matter structures.
abstract: Viscoelastic mechanical properties of the brain assessed with magnetic resonance elastography (MRE) are sensitive measures of microstructural tissue health in neurodegenerative conditions. Recent efforts have targeted measurements localized to specific neuroanatomical regions differentially affected in disease. In this work, we present a method for measuring the viscoelasticity in subcortical gray matter (SGM) structures, including the amygdala, hippocampus, caudate, putamen, pallidum, and thalamus. The method is based on incorporating high spatial resolution MRE imaging (1.6 mm isotropic voxels) with a mechanical inversion scheme designed to improve local measures in pre-defined regions (soft prior regularization [SPR]). We find that in 21 healthy, young volunteers SGM structures differ from each other in viscoelasticity, quantified as the shear stiffness and damping ratio, but also differ from the global viscoelasticity of the cerebrum. Through repeated examinations on a single volunteer, we estimate the uncertainty to be between 3 and 7% for each SGM measure. Furthermore, we demonstrate that the use of specific methodological considerations-higher spatial resolution and SPR-both decrease uncertainty and increase sensitivity of the SGM measures. The proposed method allows for reliable MRE measures of SGM viscoelasticity for future studies of neurodegenerative conditions. Hum Brain Mapp 37:4221-4233, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Department of Biomedical Engineering, University of Delaware, Newark, Delaware, 19716.
authors.forename: Curtis L
authors.initials: CL
authors.lastname: Johnson
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.
authors.forename: Hillary
authors.initials: H
authors.lastname: Schwarb
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, 03755.
authors.forename: Matthew
authors.initials: M
authors.lastname: D J McGarry
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Anderson
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Carle Neuroscience Institute, Carle Foundation Hospital, Urbana, Illinois, 61801.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Huesmann
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.
authors.forename: Bradley P
authors.initials: BP
authors.lastname: Sutton
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801.|Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, Illinois, 61820.
authors.forename: Neal J
authors.initials: NJ
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D055592:Biophysical Phenomena; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology*; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000379:methods*; D066128:Gray Matter / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D017711:Nonlinear Dynamics; D015203:Reproducibility of Results; D035501:Uncertainty; D014783:Viscosity; D055815:Young Adult
keywords: brain; elastography; gray matter; hippocampus; thalamus; viscoelasticity