title: Longitudinal measurements of postnatal rat brain mechanical properties in-vivo.
abstract: Information on pediatric brain tissue mechanical properties and, more pertinently, how they change during postnatal development remains scarce despite its importance to investigate mechanisms of neural injury. The aim of this study is to determine whether brain mechanical properties change in-vivo during early postnatal development in a rat model. Rat brain viscoelastic properties were measured longitudinally in ten healthy Sprague Dawley rats at five different time points from postnatal week one to week six using magnetic resonance elastography at 800Hz. Myelination and cell density were assessed histologically at the same time points to understand how the underlying tissue microstructure may be associated with changes in mechanical properties at different brain regions. Longitudinal changes in each variable were assessed using a generalized linear model with pairwise comparisons of means between weeks. The brain shear modulus in the cortical gray matter at postnatal week one was 6.3±0.4kPa, and increased significantly from week one to week two (pairwise comparison, p<0.01), remained stable from week two to week four and decreased significantly by week six (pairwise comparison, p<0.001). In the deep gray matter, brain tissue stiffness at postnatal week one was 6.1±2.0kPa, and increased significantly from one to week four (pairwise comparison, p<0.05) before decreasing significantly by week six (pairwise comparison, p<0.001). Stiffness changes were not directly correlated to histological observations. These data suggest that brain tissue shear modulus initially increases during a period equivalent to early childhood, and then decreases during a period equivalent to adolescence.
authors.affiliation: Neuroscience Research Australia, Margarete Ainsworth Building, Barker Street, Randwick NSW 2031, Australia; University of New South Wales, School of Medical Sciences, Wallace Wurth Building, Kensington, NSW 2052, Australia.
authors.forename: Alice C
authors.initials: AC
authors.lastname: Pong
authors.affiliation: Neuroscience Research Australia, Margarete Ainsworth Building, Barker Street, Randwick NSW 2031, Australia; University of New South Wales, School of Medical Sciences, Wallace Wurth Building, Kensington, NSW 2052, Australia.
authors.forename: Lauriane
authors.initials: L
authors.lastname: Jugé
authors.affiliation: Neuroscience Research Australia, Margarete Ainsworth Building, Barker Street, Randwick NSW 2031, Australia; Macquarie University, Department of Engineering, Faculty of Science and Engineering, NSW 2109, Australia. Electronic address: shaokoon.cheng@mq.edu.au.
authors.forename: Shaokoon
authors.initials: S
authors.lastname: Cheng
authors.affiliation: Neuroscience Research Australia, Margarete Ainsworth Building, Barker Street, Randwick NSW 2031, Australia; University of New South Wales, Prince of Wales Clinical School, Edmund Blacket Building, Kensington, NSW 2052, Australia.
authors.forename: Lynne E
authors.initials: LE
authors.lastname: Bilston
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000166:cytology / Q000000981:diagnostic imaging / Q000502:physiology*; D002452:Cell Count; D004548:Elasticity; D054459:Elasticity Imaging Techniques; D005260:Female; D016014:Linear Models; D008279:Magnetic Resonance Imaging; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014783:Viscosity
keywords: Brain; MR elastography; Viscoelastic properties