Perfusion-weighted magnetic resonance imaging thresholds identifying core, irreversibly infarcted tissue.
OBJECTIVE
Identifying core, irreversibly infarcted tissue and salvageable penumbral tissue is crucial to informed, physiologically guided decision making regarding thrombolytic and other interventional therapies in acute ischemic stroke. Pretreatment perfusion MRI offers promise as a means to differentiate core from penumbral tissues.


METHODS
Diffusion-perfusion MRIs were performed before treatment and on day 7 in patients undergoing successful vessel recanalization with intra-arterial thrombolytic therapy. Perfusion maps of the time to peak of the residue function (Tmax) were generated after deconvolution of an arterial input function. Initial perfusion abnormalities and final infarct regions were outlined by hand. Posttreatment images were coregistered to the pretreatment study. Voxel-by-voxel and volume analyses were performed to identify thresholds of perfusion abnormalities that best predict core, irreversibly infarcted tissue.


RESULTS
Fourteen patients (4 men, 10 women) with vessel recanalization were studied. Mean age was 73 years, and median entry National Institutes of Health Stroke Scale score was 12. Mean time from symptom onset to start of intra-arterial infusion was 245 minutes and to recanalization was 338 minutes. With a voxel-by-voxel analysis, Tmax > or =6 and > or =8 seconds (sensitivity, 71% and 53%; specificity, 63% and 80%) correlated most highly with day 7 final infarct. With a volume analysis, Tmax > or =6 and > or =8 seconds (r2=0.704 and r2=0.705) correlated most highly with day 7 final infarct.


CONCLUSIONS
Perfusion-weighted imaging measures of ischemia severity accurately differentiate irreversibly injured core from penumbral, salvageable tissue. The best threshold for identifying core infarcted tissue is adjusted Tmax of > or =6 to 8 seconds.
UCLA Stroke Center, UCLA Medical Center, Los Angeles, Calif, USA. lshih@caregroup.harvard.edu
Ludy C
LC
Shih
Jeffrey L
JL
Saver
Jeffry R
JR
Alger
Sidney
S
Starkman
Megan C
MC
Leary
Fernando
F
Vinuela
Gary
G
Duckwiler
Y Pierre
YP
Gobin
Reza
R
Jahan
J Pablo
JP
Villablanca
Paul M
PM
Vespa
Chelsea S
CS
Kidwell
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002544:Cerebral Infarction / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D018450:Disease Progression; D004333:Drug Administration Routes; D005260:Female; D005343:Fibrinolytic Agents / Q000008:administration & dosage; D006801:Humans; D007091:Image Processing, Computer-Assisted; D020244:Infarction, Middle Cerebral Artery / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D010959:Tissue Plasminogen Activator / Q000008:administration & dosage; D014568:Urokinase-Type Plasminogen Activator / Q000008:administration & dosage
D005343:Fibrinolytic Agents; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator