title: MR perfusion and diffusion in acute ischemic stroke: human gray and white matter have different thresholds for infarction.
abstract: It is thought that gray and white matter (GM and WM) have different perfusion and diffusion thresholds for cerebral infarction in humans. We sought to determine these thresholds with voxel-by-voxel, tissue-specific analysis of co-registered acute and follow-up magnetic resonance (MR) perfusion- and diffusion-weighted imaging. Quantitative cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) maps were analyzed from nine acute stroke patients (imaging acquired within 6 h of onset). The average values of each measure were calculated for GM and WM in normally perfused tissue, the region of recovered tissue and in the final infarct. Perfusion and diffusion thresholds for infarction were determined on a patient-by-patient basis in GM and WM separately by selecting thresholds with equal sensitivities and specificities. Gray matter has higher thresholds for infarction than WM (P<0.009) for CBF (20.0 mL/100 g min in GM and 12.3 mL/100 g min in WM), CBV (2.4 mL/100 g in GM and 1.7 mL/100 g in WM), and ADC (786 x 10(-6) mm(2)/s in GM and 708 x 10(-6) mm(2)/s in WM). The MTT threshold for infarction in GM is lower (P=0.014) than for WM (6.8 secs in GM and 7.1 secs in WM). A single common threshold applied to both tissues overestimates tissue at risk in WM and underestimates tissue at risk in GM. This study suggests that tissue-specific analysis of perfusion and diffusion imaging is required to accurately predict tissue at risk of infarction in acute ischemic stroke.
authors.affiliation: Department of Electrical and Computer Engineering, University of Calgary, Alberta, Canada.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bristow
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Simon
authors.forename: Robert A
authors.initials: RA
authors.lastname: Brown
authors.forename: Michael
authors.initials: M
authors.lastname: Eliasziw
authors.forename: Michael D
authors.initials: MD
authors.lastname: Hill
authors.forename: Shelagh B
authors.initials: SB
authors.lastname: Coutts
authors.forename: Richard
authors.initials: R
authors.lastname: Frayne
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Demchuk
authors.forename: J Ross
authors.initials: JR
authors.lastname: Mitchell
mesh_terms: D000368:Aged; D001921:Brain / Q000098:blood supply / Q000473:pathology; D002545:Brain Ischemia / Q000473:pathology / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D038524:Diffusion Magnetic Resonance Imaging / Q000592:standards*; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000592:standards*; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology*; D012039:Regional Blood Flow; D012680:Sensitivity and Specificity; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology