Penumbral mismatch is underestimated using standard volumetric methods and this is exacerbated with time.
OBJECTIVE
The mismatch between perfusion weighted images (PWI) and diffusion weighted images (DWI) using MR is increasingly being applied in patient selection for therapeutic trials. Two approaches to the calculation of the mismatch volume exist--the commonly used volumetric and the more precise co-registration method, the latter of which considers lesion topography. That there are differences in the mismatch volume analysed by each method and that these are time dependent was hypothesised.


METHODS
Patients within 48 h of ischaemic stroke onset had baseline MR PWI/DWI mismatch and T2 outcome volumes at 3 months. Volumetric mismatch volume was defined as PWI minus DWI lesion. Co-registration mismatch volume was defined as the PWI defect lesion not overlapped by the co-registered DWI lesion.


RESULTS
72 patients of median age 74.0 years were studied. Median baseline MR was at 5.9 h (IQR 3.0, 20.4 h) after stroke onset. Consistent underestimation of the mismatch volume occurred using the volumetric method (volumetric median 9.3 ml, IQR 0, 63 ml; co-registration median 20.1 ml, IQR 3.2, 69.8 ml; p<0.0001). This difference increased with time from stroke onset (p = 0.006).


CONCLUSIONS
Volumetric analysis consistently underestimates the PWI/DWI mismatch volume compared with the more precise co-registration method. This effect increases with time.
National Stroke Research Institute, Austin Health, University of Melbourne, 300 Waterdale Rd, Heidelberg West, Vic 3081, Australia.
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H
Ma
J A
JA
Zavala
H
H
Teoh
L
L
Churilov
M
M
Gunawan
J
J
Ly
P
P
Wright
T
T
Phan
S
S
Arakawa
S M
SM
Davis
G A
GA
Donnan
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000150:complications / Q000473:pathology; D015331:Cohort Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020521:Stroke / Q000175:diagnosis / Q000473:pathology*; D055815:Young Adult