title: Magnetization transfer and diffusion imaging of acute axonal damage in the cerebral peduncle following hypoxia-ischemia in neonatal rats.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) of axonal degenerative changes in the cerebral peduncle of the corticospinal tract following cerebral hypoxic-ischemic damage might distinguish infants most appropriate for receiving prompt treatment. The optimal MRI sequence for very early diagnosis of axonal degenerative changes is unknown. We hypothesized that magnetization transfer ratio (MTR) imaging would be more sensitive than traditional MRI, e.g., T(2) or diffusion weighted imaging.
  
  
  METHODS
  Transient unilateral cerebral hypoxia-ischemia was produced in the neonatal rat followed by MRI of changes in T(2), the apparent diffusion coefficient (ADC) of water, and MTR, with a focus on the parietal cortex (an ischemic damaged region) and the cerebral peduncle (remote within the corticospinal tract). Rats were imaged at 2 h, 1 d, or 1 wk postinsult.
  
  
  RESULTS
  In the cerebral peduncle, MTR and T(2) responded similarly, with alterations occurring ipsilaterally at 1 d postinsult. ADC was most sensitive for detecting changes as early as 2 h postinsult, and this corresponded to a reduced staining of axonal filaments ipsilaterally.
  
  
  CONCLUSIONS
  MTR and T(2) imaging have comparable sensitivity for distinguishing early axonal damage in the cerebral peduncle. ADC imaging is highly sensitive for detecting early disruption of corticospinal axons, supporting its potential hyperacute diagnostic use clinically.
authors.affiliation: Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada. utuor@ucalgary.ca
authors.forename: Ursula I
authors.initials: UI
authors.lastname: Tuor
authors.forename: Min
authors.initials: M
authors.lastname: Qiao
authors.forename: Melissa
authors.initials: M
authors.lastname: Morgunov
authors.forename: Emily
authors.initials: E
authors.lastname: Fullerton
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Foniok
authors.forename: Adam
authors.initials: A
authors.lastname: Kirton
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D051381:Rats; D013681:Tegmentum Mesencephali / Q000166:cytology / Q000473:pathology*; D013997:Time Factors