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Acute Brain Infarct: Detection and Delineation with CT Angiographic Source Images versus Nonenhanced CT Scans¹

¹ From the Departments of Neurology (E.C.S.C., K.L.F., A.B.S., W.J.K.) and Radiology (L.R., M.E.C., E.F.H., G.J.H., R.G.G., M.H.L.), Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, GRB-239, Boston, MA 02114-2622; and Department of Neurology, University of California at San Francisco, San Francisco, Calif (W.S.S.). Received June 13, 2006; revision requested August 14; revision received September 18; accepted October 25; final version accepted December 15. Supported by National Institutes of Health grant AHRQ RO1 HS11392. E.C.S.C. supported by a scholarship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brasília, Brazil. Address correspondence to M.H.L. (e-mail: mlev{at}partners.org).

Purpose: To retrospectively compare sensitivity and specificity of admission nonenhanced computed tomographic (CT) scans with those of CT angiographic source images in detection of early ischemic changes in middle cerebral artery (MCA) stroke and to retrospectively compare admission nonenhanced CT scans with CT angiographic source images in delineation of final infarct extent, with follow-up images as reference.

Materials and Methods: Informed consent and institutional review board approval were received for this HIPAA-compliant study. Nonenhanced scans and angiographic source images obtained within 12 hours of symptom onset in 51 patients suspected of having MCA stroke were reviewed. Two blinded neuroimagers rated presence and extent of hypoattenuation on nonenhanced scans and angiographic source images with Alberta Stroke Programme Early CT Score (ASPECTS). Level of certainty for hypoattenuation detection was assigned a grade with a five-point scale. With receiver operating characteristic (ROC) curve analysis, nonenhanced scans and angiographic source images were compared for stroke detection. For stroke delineation, linear regression coefficients determined correlations of ASPECTS for nonenhanced scans and angiographic source images with ASPECTS for follow-up images. Multiple linear regressions were used to compare these correlations.

Results: Follow-up nonenhanced CT scans, diffusion-weighted magnetic resonance (MR) images, or fluid-attenuated inversion-recovery MR images were obtained (mean time to follow-up, 5.4 days); 33 patients had infarction. With level of certainty cutoff score of 4 or greater (probable, definite) for ischemic hypoattenuation, sensitivity for detection of acute stroke was 48% (nonenhanced scans) and 70% (angiographic source images) (P = .04, ROC analysis); specificity was 100% for both. Linear regression revealed R² = 0.42 (P < .001) for correlation between delineation of stroke on nonenhanced scans and on follow-up images evaluated with ASPECTS and 0.73 (P < .001) for correlation between delineation on angiographic source images and follow-up images evaluated with ASPECTS (P < .001, nonenhanced scans vs angiographic source images).

Conclusion: CT angiographic source images, compared with nonenhanced CT scans, are more sensitive in detection of early irreversible ischemia and more accurate for prediction of final infarct volume.

© RSNA, 2007