Clinical Investigative Study Reproducibility of ABC/2 Method to Determine Infarct Volume and Mismatch Percentage with CT Perfusion Kris F. French, MD, Julie K. Martinez, RN, Adam H. DeHavenon, MD, Natalie R. Weathered, MD, Matthew Grantz, MD, Shawn M. Smith, MD, Michael Wilder, MD, Ulrich A. Rassner, MD, John C. Kircher, PhD, L.Dana. Dewitt, MD, Jana J. Wold, MD, Robert E. Hoesch, MD, PhD From the Department of Neurology, University of Utah, Salt Lake City, UT (KFF, JKM, AHD, NRW, MG, LD, JJW); Department of Neuroradiology, University of Utah, Salt Lake City, UT (MW, UAR); Department of Educational Psychology, University of Utah, Salt Lake City, UT (JCK); Department of Neurocritical Care (SMS, REH). Keywords: Stroke, computed tomogra- phy, thrombolytics. Acceptance: Received July 25, 2012, and in revised form October 12, 2012. Ac- cepted for publication November 8, 2012. Correspondence: Address correspon- dence to to Kris French, M.D., Univer- sity of Utah, Clinical Neurosciences Cen- ter, 175 N Medical Dr E, Salt Lake City, UT 84132. E-mail: Kris.french@hsc. utah.edu. Contributorship statement: All authors contributed to the work of this paper. Dr. Hoesch and Dr. Wold reviewed and su- pervised all work and the process of the study and generation of the manuscript. Dr. French is the corresponding and first author of the paper. Drs. DeHavenon, Weathered, Grantz, Wilder, Smith, and DeWitt were all involved in reviewing and editing the manuscript as well as involve- ment in blinded viewing of the data as described in the manuscript. Dr. Rassner was involved in the methods section es- pecially with the neuroradiology descrip- tion. Dr. Kircher was involved with the statistics generation. Sources of Funding: There were no sources of funding for this study. Disclosures: Kris French: None; Julie Martinez: None; Adam DeHavenon: None; Natalie Weathered: None; John Kircher: None; Ulrich Rassner: None; Matthew Grantz: None; Shawn Smith: None; Michael Wilder: None; L.D. Dewitt: None; Jana Wold: None; Robert Hoesch: None J Neuroimaging 2014;24:232-237. DOI: 10.1111/jon.12001 ABSTRACT BACKGROUND Our aim is to implement a simple, rapid, and reliable method using computed tomog- raphy perfusion imaging and clinical judgment to target patients for reperfusion ther- apy in the hyper-acute stroke setting. We introduce a novel formula (1–infarct volume [CBV]/penumbra volume [MTT] × 100%) to quantify mismatch percentage. METHODS Twenty patients with anterior circulation strokes who underwent CT perfusion and received intravenous tissue plasminogen activator (IV tPA) were analyzed retrospectively. Nine blinded viewers determined volume of infarct and ischemic penumbra using the ABC/2 method and also the mismatch percentage. RESULTS Interrater reliability using the volumetric formula (ABC/2) was very good (intraclass correlation [ICC] = .9440 and ICC = .8510) for hemodynamic parameters infarct (CBV) and penumbra (MTT). ICC coefficient using the mismatch formula (1–MTT/CBV × 100%) was good (ICC of .635). CONCLUSIONS The ABC/2 method of volume estimation on CT perfusion is a reliable and efficient ap- proach to determine infarct and penumbra volumes. The 1–CBV/MTT × 100% formula produces a mismatch percentage assisting providers in communicating the proportion of salvageable brain and guides therapy in the setting of patients with unclear time of onset with potentially salvageable tissue who can undergo mechanical retrieval or intraarterial thrombolytics. Introduction Brain imaging is an essential element in the approach to patients with hyperacute and acute ischemic stroke. Determination of infarct volume relative to the volume of tissue at risk (ischemic penumbra) can be an important step in planning thromboly- sis, interventional therapy, or immediate poststroke care, such as induced or permissive hypertension. 1 Several methods are available to measure volume on head imaging including visual 232 Copyright ◦ C 2013 by the American Society of Neuroimaging