Optimal Tmax threshold for predicting penumbral tissue in acute stroke.
OBJECTIVE
We sought to assess whether the volume of the ischemic penumbra can be estimated more accurately by altering the threshold selected for defining perfusion-weighting imaging (PWI) lesions.


METHODS
DEFUSE is a multicenter study in which consecutive acute stroke patients were treated with intravenous tissue-type plasminogen activator 3 to 6 hours after stroke onset. Magnetic resonance imaging scans were obtained before, 3 to 6 hours after, and 30 days after treatment. Baseline and posttreatment PWI volumes were defined according to increasing Tmax delay thresholds (>2, >4, >6, and >8 seconds). Penumbra salvage was defined as the difference between the baseline PWI lesion and the final infarct volume (30-day fluid-attenuated inversion recovery sequence). We hypothesized that the optimal PWI threshold would provide the strongest correlations between penumbra salvage volumes and various clinical and imaging-based outcomes.


RESULTS
Thirty-three patients met the inclusion criteria. The correlation between infarct growth and penumbra salvage volume was significantly better for PWI lesions defined by Tmax >6 seconds versus Tmax >2 seconds, as was the difference in median penumbra salvage volume in patients with a favorable versus an unfavorable clinical response. Among patients who did not experience early reperfusion, the Tmax >4 seconds threshold provided a more accurate prediction of final infarct volume than the >2 seconds threshold.


CONCLUSIONS
Defining PWI lesions based on a stricter Tmax threshold than the standard >2 seconds delay appears to provide more a reliable estimate of the volume of the ischemic penumbra in stroke patients imaged between 3 and 6 hours after symptom onset. A threshold between 4 and 6 seconds appears optimal for early identification of critically hypoperfused tissue.
Olivot
Jean-Marc
JM
Department of Neurology and Neurological Sciences and the Stanford Stroke Center, Stanford University Medical Center, Palo Alto, CA 94304, USA. jmolivot@stanford.edu
Mlynash
Michael
M
Thijs
Vincent N
VN
Kemp
Stephanie
S
Lansberg
Maarten G
MG
Wechsler
Lawrence
L
Bammer
Roland
R
Marks
Michael P
MP
Albers
Gregory W
GW
D000368:Aged; D001921:Brain / Q000473:pathology; D002545:Brain Ischemia / Q000175:diagnosis / Q000628:therapy; D002544:Cerebral Infarction / Q000473:pathology / Q000628:therapy; D017352:Echo-Planar Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D011237:Predictive Value of Tests; D018046:Protein C Inhibitor / Q000627:therapeutic use; D015427:Reperfusion Injury / Q000473:pathology / Q000628:therapy; D020521:Stroke / Q000175:diagnosis* / Q000628:therapy; D015912:Thrombolytic Therapy; D016896:Treatment Outcome
D018046:Protein C Inhibitor