title: Search for a map and threshold in perfusion MRI to accurately predict tissue fate: a protocol for assessing lesion growth in patients with persistent vessel occlusion.
abstract: BACKGROUND
  The MRI-based mismatch concept has been used to estimate the risk of infarction in ischemic stroke. Based on multiple studies on magnetic resonance perfusion imaging, it seems unlikely that any perfusion parameter threshold will provide a reliable prediction of radiological or clinical outcome for all patients. The goal of our study was to find a minimally biased yet maximally useful perfusion postprocessing protocol which would offer the treating physician a useful estimate of tissue fate.
  
  
  METHODS
  One hundred and forty-five acute ischemic stroke patients, admitted within 24 h after stroke to the Charité-University Medicine Hospital in Berlin between March 2008 and November 2009, were included in this study. Using three different software packages (Perfscape/Neuroscape, PMA and Stroketool), maps of mean transit time, cerebral blood flow (CBF) and T(max) were created. Three different thresholds were applied on each parameter map and subsequent volumes of hypoperfused tissue were calculated.
  
  
  RESULTS
  Overall, the maps and thresholds giving the least amount of overestimation of the final infarct volume were T(max) 8 s in Perfscape/Neuroscape, CBF 20 ml/100 g/min in PMA and CBF 15% (of the highest value on the scale for a given patient) in Stroketool. In patients with persistent vessel occlusion, a CBF map with a restrictive threshold showed volumes of tissue at definite risk of infarction in up to 100% of patients. The additional use of a CBF map with a high threshold enabled identification of patients without penumbras.
  
  
  CONCLUSIONS
  No combination of software, map and threshold was able to give a reliable estimate of tissue fate for either all patients or any subgroup of patients. However, in patients with vessel occlusion, combination of a CBF map with a low and a high threshold can enable calculation of the minimum volume of brain tissue that will inevitably be lost if the occlusion persists.
authors.affiliation: Center for Stroke Research Berlin (CSB), Charité-University Medicine Berlin, Campus Benjamin Franklin, Berlin, Germany. ivana.galinovic@charite.de
authors.forename: Ivana
authors.initials: I
authors.lastname: Galinovic
authors.forename: Ann-Christin
authors.initials: AC
authors.lastname: Ostwaldt
authors.forename: Carina
authors.initials: C
authors.lastname: Soemmer
authors.forename: Helena
authors.initials: H
authors.lastname: Bros
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hotter
authors.forename: Peter
authors.initials: P
authors.lastname: Brunecker
authors.forename: Wolf U
authors.initials: WU
authors.lastname: Schmidt
authors.forename: Jan
authors.initials: J
authors.lastname: Jungehülsing
authors.forename: Jochen B
authors.initials: JB
authors.lastname: Fiebach
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000098:blood supply / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D002561:Cerebrovascular Disorders / Q000175:diagnosis* / Q000473:pathology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods; D011379:Prognosis; D012039:Regional Blood Flow / Q000502:physiology; D012189:Retrospective Studies; D012984:Software; D020521:Stroke / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology