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NEUROLOGY 2009;72:2104-2110
© 2009 American Academy of Neurology

ABC/2 for rapid clinical estimate of infarct, perfusion, and mismatch volumes

J. R. Sims, MD, L. Rezai Gharai, MD, P. W. Schaefer, MD, M. Vangel, PhD, E. S. Rosenthal, MD, M. H. Lev, MD and L. H. Schwamm, MD

From the Departments of Neurology (J.R.S., L.H.S.) and Radiology (J.R.S., L.R.G., P.W.S., M.V., E.S.R., M.H.L.), Massachusetts General Hospital, Harvard Medical School, Charlestown, MA.

Address correspondence and reprint requests to Dr. John R. Sims, Massachusetts General Hospital, CNY149 Rm 6403, 13th Street, Charlestown, MA 02129 jsims{at}partners.org.

Background: Rapid and easy clinical assessments for volumes of infarction and perfusion mismatch are needed. We tested whether simple geometric models generated accurate estimates of these volumes.

Methods: Acute diffusion-weighted image (DWI) and perfusion (mean transit time [MTT]) in 63 strokes and established infarct volumes in 50 subacute strokes were measured by computerized planimetry. Mismatch was defined as MTT/DWI ≥ 1.2. Observers, blinded to planimetric values, measured lesions in three perpendicular axes A, B, and C. Geometric estimates of sphere, ellipsoid, bicone, and cylinder were compared to planimetric volume by least-squares linear regression.

Results: The ABC/2 formula (ellipsoid) was superior to other geometries for estimating volume of DWI (slope 1.16, 95% confidence interval [CI] 0.94 to 1.38; R2 = 0.91, p = 0.001) and MTT (slope 1.11, 95% CI 0.99 to 1.23; R2 = 0.89, p = 0.001). The intrarater and interrater reliability for ABC/2 was high for both DWI (0.992 and 0.965) and MTT (0.881 and 0.712). For subacute infarct, the ABC/2 formula also best estimated planimetric volume (slope 1.00, 95% CI 0.98 to 1.19; R2 = 0.74, p = 0.001). In general, sphere and cylinder geometries overestimated all volumes and bicone underestimated all volumes. The positive predictive value for mismatch was 92% and negative predictive value was 33%.

Conclusions: Of the models tested, ABC/2 is reproducible, is accurate, and provides the best simple geometric estimate of infarction and mean transit time volumes. ABC/2 has a high positive predictive value for identifying mismatch greater than 20% and might be a useful tool for rapid determination of acute stroke treatment.

Abbreviations: CBF = cerebral blood flow; CBV = cerebral blood volume; CI = confidence interval; DWI = diffusion-weighted image; FOV = field of view; ICH = intracerebral hemorrhage; MCA = middle cerebral artery; MTT = mean transit time; PWI = perfusion-weighted imaging; ROI = region of interest; TE = echo time; TR = repetition time.

Supported by the American Heart Association, Scientist Development Grant 0535138N and NIH K08 NS049241.

Disclosure: The authors report no disclosures.

Medical Devices: High Speed Advantage helical CT scanner and Signa scanner (GE Medical Systems, Milwaukee, WI).

Received September 5, 2008. Accepted in final form March 30, 2009.






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