title: Magnetization transfer imaging shows tissue abnormalities in the reversible penumbra.
abstract: OBJECTIVE
  In the concept of ischemic penumbra, the volume of salvaged penumbra is considered as the volume of FLAIR normalization on follow-up MRI compared with early diffusion and perfusion abnormalities. Using magnetization transfer imaging, very sensitive to macromolecular disruption, we investigated whether FLAIR normalization was a good marker for tissue full recovery.
  
  
  METHODS
  We prospectively included 30 patients with acute middle cerebral artery stroke. Diffusion-weighted imaging (DWI) and perfusion-weighted imaging were performed within 12 hours after onset (MRI.1), and the final infarct was documented by MRI with FLAIR and magnetization transfer at 1-month follow-up (MRI.2). We compared magnetic transfer ratio of a normal region with values measured at 1 month (MRI.2) in 4 regions of interest: (1) the initial DWI hypersignal (CORE=DWI MRI.1); (2) the infarct growth area (infarct growth=FLAIR MRI.2-DWI MRI.1); (3) the hypoperfused area that normalized (reversible perfusion abnormalities=perfusion-weighted imaging MRI.1-FLAIR_ MRI.2); and (4) the early DWI abnormalities that normalized (reversible diffusion abnormalities=DWI MRI.1- FLAIR_MRI.2).
  
  
  RESULTS
  In comparison with values obtained in normal tissue (magnetic transfer ratio=49.8%, SD=1.9), magnetic transfer ratio at 1 month was significantly decreased in reversible perfusion abnormalities (45.2%, SD=2.5; P<0.0001) and reversible diffusion abnormalities (43.2%, SD=2.8; P=0.0156). It was also markedly reduced, as expected, in the CORE (40.9%, SD=5.2) and infarct growth regions (43.1%, SD=2.0).
  
  
  CONCLUSIONS
  Magnetic transfer ratio assessed presence of microstructural damages in the MRI-defined salvaged penumbra. This may imply cellular loss and partial infarction. Evaluation of the efficacy of therapies that promote reperfusion or neuroprotection may benefit from this additional information.
authors.affiliation: CHU de Bordeaux, Université Victor Segalen Bordeaux 2, Service de Neuroradiologie diagnostique et thérapeutique, Place Amélie Raba-Léon, Bordeaux, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Tourdias
authors.forename: Vincent
authors.initials: V
authors.lastname: Dousset
authors.forename: Igor
authors.initials: I
authors.lastname: Sibon
authors.forename: Eric
authors.initials: E
authors.lastname: Pele
authors.forename: Patrice
authors.initials: P
authors.lastname: Menegon
authors.forename: Julien
authors.initials: J
authors.lastname: Asselineau
authors.forename: Chahin
authors.initials: C
authors.lastname: Pachai
authors.forename: François
authors.initials: F
authors.lastname: Rouanet
authors.forename: Philip
authors.initials: P
authors.lastname: Robinson
authors.forename: Geneviève
authors.initials: G
authors.lastname: Chene
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Orgogozo
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D002545:Brain Ischemia / Q000175:diagnosis* / Q000473:pathology; D002560:Cerebrovascular Circulation; D004058:Diffusion; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009474:Neurons / Q000378:metabolism; D020521:Stroke / Q000175:diagnosis* / Q000473:pathology