Assessment of suitability of thrombolysis in middle cerebral artery infarction: a proof of concept study of a stereologically-based technique.
BACKGROUND
The extent of cerebral ischemia, assessed by the Alberta Stroke Program Early CT Score (ASPECTS) method and unaided visual determination of the CT Summit Criterion, correlates with increased risk of intracerebral hemorrhage following rt-PA administration. Concerns about the accuracy of the unaided visual assessment in the estimation of infarct size and the conservative nature of the ASPECTS method led us to develop a new method (MCAGrid) based on stereological grid counting and a digital atlas of the middle cerebral artery (MCA) infarct territory.


METHODS
We tested the hypotheses that the stereological method increases the accuracy of infarct estimation and that the number of patients deemed eligible for thrombolysis is greater with this method than with existing methods. Four experienced radiologists with extensive neuroradiological experience examined the CT images of 19 patients with MCA territory stroke and determined patient eligibility for thrombolysis by: unaided visual determination of the CT Summit Criterion, MCAGrid, and the ASPECTS score. The chi(2) test was used to compare the differences in the number of patients deemed 'eligible' for thrombolysis by the 3 imaging methods. Further, the unaided visual assessment and MCAGrid were compared with volumes calculated following manual segmentation of infarct, and the sensitivity, specificity and positive and negative likelihood ratios for these techniques were calculated.


RESULTS
In general, MCAGrid was better than unaided visual assessment in the prediction of >1/3 involvement of the MCA territory by infarct. The number of patients considered as 'eligible' for thrombolysis based on imaging criteria was significantly lower when ASPECTS criteria (15/76) were used than when unaided visual determination of the CT Summit Criterion (32/76; p < 0.01) or MCAGrid (59/76; p < 0.001) criteria were used.


CONCLUSIONS
The choice of methods for rating infarct extent affects the number of patients 'eligible' for thrombolysis significantly. Furthermore, MCAGrid increased the accuracy with which infarct extent was estimated. These results provide justification for a prospective study of this technique in the setting of acute stroke.
Phan
Thanh G
TG
National Stroke Research Institute, Melbourne, Australia.
Donnan
Geoffrey A
GA
Koga
Masatoshi
M
Mitchell
L Anne
LA
Molan
Maurice
M
Fitt
Gregory
G
Chong
Winston
W
Holt
Michael
M
Reutens
David C
DC
D000368:Aged; D000369:Aged, 80 and over; D002543:Cerebral Hemorrhage / Q000139:chemically induced* / Q000000981:diagnostic imaging; D005260:Female; D005343:Fibrinolytic Agents / Q000009:adverse effects*; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000150:complications* / Q000000981:diagnostic imaging / Q000188:drug therapy; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D018579:Patient Selection; D011237:Predictive Value of Tests; D011994:Recombinant Proteins / Q000009:adverse effects; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D020521:Stroke / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000209:etiology; D015912:Thrombolytic Therapy; D010959:Tissue Plasminogen Activator / Q000009:adverse effects*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
D005343:Fibrinolytic Agents; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator