title: A novel method to assess pial collateralization from stroke perfusion MRI: subdividing Tmaxinto anatomical compartments.
abstract: OBJECTIVE
  To develop and validate a quantitative and observer-independent method to evaluate pial collateral circulation by DSC-perfusion MRI and test whether this novel method delivers diagnostic information which is redundant to or independent from conventional penumbra imaging by the mismatch approach.
  
  
  METHODS
  We retrospectively identified 47 patients with M1 occlusion who underwent MR diffusion/perfusion imaging and mechanical thrombectomy at our facility. By automated registration and segmentation, Tmaxdelays were attributed specifically to the pial, cortical and parenchymal compartments. The resulting pial volumes at delay were defined as the pial Tmaxmap-assessed collateral score (TMACS) and correlated with gold standard digital subtraction angiography (DSA). Mismatch ratio was assessed by conventional penumbra defining MRI criteria.
  
  
  RESULTS
  Strong correlation was found between TMACS and angiographically assessed collateral score (Pearson ρ = -0.74, p < 0.001). In multiple logistic regression, both good collaterals according to TMACS [OR 4.3 (1.1-19, p = 0.04)] and mismatch ratio ≥ 3.5 [OR 12.3 (1.88-249, p = 0.03)] were independent predictors of favourable clinical outcome.
  
  
  CONCLUSIONS
  Perfusion delay in the pial compartment, as evaluated by TMACS, closely reflects the extent of pial collaterals in gold-standard DSA. TMACS and mismatch ratio were found to be complementary predictors of a favourable clinical outcome, each adding independent predictive information.
  
  
  CONCLUSIONS
  • MRI-DSC perfusion delay specific in the pial compartment reflects leptomeningeal collateralization. • A novel quantitative- and observer-independent marker of collateral status (TMACS) is introduced. • Quantification of collateral status leads to an independent predictor of neurological outcome.
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany. arne.potreck@med.uni-heidelberg.de.
authors.forename: Arne
authors.initials: A
authors.lastname: Potreck
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Fatih
authors.initials: F
authors.lastname: Seker
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Angelika
authors.initials: A
authors.lastname: Hoffmann
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Pfaff
authors.affiliation: Department of Neurology, Heidelberg University Hospital, Heidelberg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Nagel
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bendszus
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Heiland
authors.affiliation: Department of Neuroradiology, Heidelberg University Hospital, INF 400, 69120, Heidelberg, Germany.
authors.forename: Mirko
authors.initials: M
authors.lastname: Pham
mesh_terms: D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D002550:Cerebral Veins / Q000000981:diagnostic imaging*; D003097:Collateral Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D020521:Stroke / Q000000981:diagnostic imaging* / Q000503:physiopathology*
keywords: Collateral circulation; DSC-perfusion-weighted MRI; MRI; Stroke