This Article Full Text Full Text (PDF) All Versions of this Article: 39/4/1171    most recent STROKEAHA.107.502104v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Ay, H. Articles by Sorensen, A. G. PubMed PubMed Citation Articles by Ay, H. Articles by Sorensen, A. G. Pubmed/NCBI databases Medline Plus Health Information Stroke Related Collections Acute Cerebral Infarction Computerized tomography and Magnetic Resonance Imaging

(Stroke. 2008;39:1171.)
© 2008 American Heart Association, Inc.

Original Contributions

Interexaminer Difference in Infarct Volume Measurements on MRI

A Source of Variance in Stroke Research

Hakan Ay, MD; E. Murat Arsava, MD; Mark Vangel, PhD; Banu Oner, MD; Mingwang Zhu, MD; Ona Wu, PhD; Aneesh Singhal, MD; Walter J. Koroshetz, MD A. Gregory Sorensen, MD

From the Stroke Service, Department of Neurology (H.A., A.B.S.) and A.A. Martinos Center for Biomedical Imaging (H.A., E.M.A., M.V., B.O., M.Z., O.W., A.G.S.), Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Mass; and the National Institute of Neurological Disorders and Stroke (W.J.K.), NIH, Bethesda, Md.

Correspondence to Hakan Ay, MD, A.A. Martinos Center for Biomedical Imaging and Stroke Service, Departments of Neurology and Radiology, Massachusetts General Hospital, Harvard Medical School, 149 13th Street, Room 2301, Charlestown MA 02129. E-mail hay{at}partners.org

Background and Purpose— The measurement of ischemic lesion volume on diffusion- (DWI) and perfusion-weighted MRI (PWI) is examiner dependent. We sought to quantify the variance imposed by measurement error in DWI and PWI lesion volume measurements in ischemic stroke.

Methods— Fifty-eight consecutive patients with DWI and PWI within 12 hours of symptom onset and follow-up MRI on day-5 were studied. Two radiologists blinded to each other measured lesion volumes by manual outlining on each image. Interexaminer reliability was evaluated by intraclass correlation coefficients (ICC) and relative paired difference or RPD (ratio of difference between 2 measurements to their mean). The ratio of between-examiner variability to between-subject variability (variance ratio) was calculated for each imaging parameter.

Results— The correlation (ICC) between examiners ranged from 0.93 to 0.99. The median RPD was 10.0% for DWI, 14.1% for mean transit time, 18.9% for cerebral blood flow, 21.0% for cerebral blood volume, 16.8% for DWI/MTT mismatch, and 6.3% for chronic T2-weighted images. There was negative correlation between RPD and lesion volume in all but chronic T2-weighted images. The variance ratio ranged between 0.02 and 0.10.

Conclusion— Despite high correlation between volume measurements of abnormal regions on DWI and PWI by different examiners, substantial differences in individual measurements can still occur. The magnitude of variance from measurement error is primarily determined by the type of imaging and lesion volume. Minimizing this source of variance will better enable imaging to deliver on its promise of smaller sample size.

Key Words: acute stroke • diffusion-weighted imaging • MRI • neuroradiology