Refining the perfusion-diffusion mismatch hypothesis

• Published in: Stroke (1970) Vol. 36; no. 6; pp. 1153 - 1159
• Main Authors: BUTCHER, K. S, PARSONS, M, TRESS, B, DONNAN, G, DAVIS, S, MACGREGOR, L, BARBER, P. A, CHALK, J, BLADIN, C, LEVI, C, KIMBER, T, SCHULTZ, D, FINK, J
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 01.06.2005
• Subjects: Aged; Biological and medical sciences; Brain Ischemia - pathology; Cerebral Arteries - pathology; Cerebral Infarction; Cerebrovascular Circulation; Diffusion; Diffusion Magnetic Resonance Imaging - methods; Echo-Planar Imaging - methods; Humans; Image Processing, Computer-Assisted; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Angiography - methods; Medical sciences; Middle Aged; Nervous system; Neurology; Perfusion; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Stroke - diagnosis; Stroke - pathology; Thrombolytic Therapy; Time Factors; Treatment Outcome; Ultrasonic investigative techniques; Vascular diseases and vascular malformations of the nervous system; Vascular disease; Stroke; Nervous system diseases; Central nervous system disease; thrombolysis; Cardiovascular disease; magnetic resonance imaging, diffusion-weighted; Diffusion; magnetic resonance imaging, perfusion-weighted; Nuclear magnetic resonance imaging; Cerebrovascular disease; Cerebral disorder
• ISSN: 0039-2499; 1524-4628
• DOI: 10.1161/01.str.0000166181.86928.8b

The Echoplanar Imaging Thrombolysis Evaluation Trial (EPITHET) tests the hypothesis that perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch predicts the response to thrombolysis. There is no accepted standardized definition of PWI-DWI mismatch. We compared common mismatch definitions in the initial 40 EPITHET patients. Raw perfusion images were used to generate maps of time to peak (TTP), mean transit time (MTT), time to peak of the impulse response (Tmax) and first moment transit time (FMT). DWI, apparent diffusion coefficient (ADC), and PWI volumes were measured with planimetric and thresholding techniques. Correlations between mismatch volume (PWIvol-DWIvol) and DWI expansion (T2(Day 90-vol)-DWI(Acute-vol)) were also assessed. Mean age was 68+/-11, time to MRI 4.5+/-0.7 hours, and median National Institutes of Health Stroke Scale (NIHSS) score 11 (range 4 to 23). Tmax and MTT hypoperfusion volumes were significantly lower than those calculated with TTP and FMT maps (P<0.001). Mismatch > or =20% was observed in 89% (Tmax) to 92% (TTP/FMT/MTT) of patients. Application of a +4s (relative to the contralateral hemisphere) PWI threshold reduced the frequency of positive mismatch volumes (TTP 73%/FMT 68%/Tmax 54%/MTT 43%). Mismatch was not significantly different when assessed with ADC maps. Mismatch volume, calculated with all parameters and thresholds, was not significantly correlated with DWI expansion. In contrast, reperfusion was correlated inversely with infarct growth (R=-0.51; P=0.009). Deconvolution and application of PWI thresholds provide more conservative estimates of tissue at risk and decrease the frequency of mismatch accordingly. The precise definition may not be critical; however, because reperfusion alters tissue fate irrespective of mismatch.