title: Quantitative T2* mapping reveals early temporo-spatial dynamics in an ischemic stroke model.
abstract: BACKGROUND
  Oxyhemoglobin-sensitive sequences, namely T2*, can indirectly depict changes in oxygen extraction. Purpose of this study was to investigate the dynamics of T2* changes in ischemic tissue.
  
  
  METHODS
  We investigated earliest temporo-spatial dynamics within ischemic tissue, measured with quantitative T2* imaging in the histologically defined infarct core and surrounding surviving tissue. Middle cerebral artery occlusion (MCAO) was induced by a filament model in mice. Serial multiple gradient-echo T2* sequences and diffusion-weighted images were acquired for 60min after MCAO and repeated for 60min after recanalization. T2* maps were co-registered with histology and T2* changes were compared to the contralateral hemisphere.
  
  
  RESULTS
  Within the histologically defined infarct core, relative T2* values decreased significantly by -10.8±2.8% (P=0.003) compared to the contralateral hemisphere within 3.5±0.7min after MCAO. Relative T2* values in volume exceeding the histologically determined infarct core were significantly less decreased (-6.7±2.1%; P=0.02) and increased after recanalization (+3.9±1.9%; P=0.045). Volume with T2* decrease showed continuous growth over 60min after MCAO (P=0.002) and decreased during 60min after recanalization (P=0.026), showing most significant correlations between infarct core volume and T2* abnormality volume (r=0.66; P=0.037) of the last image acquired after recanalization.
  
  
  CONCLUSIONS
  To our best knowledge, this is the first application of non-invasive quantitative T2* measurements to assess changes in levels of deoxyhemoglobin as an indirect biomarker for metabolic impairment in ischemic tissue.
  
  
  CONCLUSIONS
  Quantitative T2* imaging might be a feasible tool to indicate change of oxygenation in acute stroke imaging, without administration of contrast agent.
authors.affiliation: Department of Neuroradiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. Electronic address: alexandra.gersing@ucsf.edu.
authors.forename: Alexandra S
authors.initials: AS
authors.lastname: Gersing
authors.affiliation: Department of Neurosurgery, University Hospital of Cologne, Cologne, Germany. Electronic address: andrea.faymonville@uk-koeln.de.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Faymonville
authors.affiliation: Department of Neuroradiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. Electronic address: benedikt.schwaiger@tum.de.
authors.forename: Benedikt J
authors.initials: BJ
authors.lastname: Schwaiger
authors.affiliation: Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address: frank.leypoldt@uksh.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Leypoldt
authors.affiliation: Department of Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address: s.siemonsen@uke.de.
authors.forename: Susanne
authors.initials: S
authors.lastname: Siemonsen
authors.affiliation: Department of Neuroradiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. Electronic address: claus.zimmer@tum.de.
authors.forename: Claus
authors.initials: C
authors.lastname: Zimmer
authors.affiliation: Department of Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address: t.magnus@uke.de.
authors.forename: Tim
authors.initials: T
authors.lastname: Magnus
authors.affiliation: Department of Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address: fiehler@uke.de.
authors.forename: Jens
authors.initials: J
authors.lastname: Fiehler
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000175:diagnosis*; D004195:Disease Models, Animal; D020244:Infarction, Middle Cerebral Artery / Q000175:diagnosis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020521:Stroke / Q000175:diagnosis*; D013997:Time Factors
keywords: MR imaging brain; Stroke; T2*