Perfusion CT Improves Diagnostic Accuracy for Hyperacute Ischemic Stroke in the 3-Hour Window: Study of 100 Patients with Diffusion MRI Confirmation

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Abstract

Purpose: Conventional noncontrast CT (NCCT) is insensitive to hyperacute cerebral infarction in the first 3 h. Our aim was to determine if CT perfusion (CTP) can improve diagnostic accuracy over NCCT for patients presenting with stroke symptoms in the 3-hour window. Methods: Consecutive patients presenting to our emergency department with symptoms of ischemic stroke <3 h old and receiving NCCT and CTP as part of their triage evaluation were retrospectively reviewed. Patients with follow-up diffusion-weighted MRI (DWI) <7 days from ictus were included. Two readers rated the NCCT and CTP for evidence of acute infarct and its vascular territory. CTP selectively covered 24 mm of brain centered at the basal ganglia with low relative cerebral blood volume in a region of low cerebral blood flow or elevated time to peak as the operational definition for infarction. A third reader rated all follow-up DWI for acute infarct and its vascular territory as the reference standard. Sensitivity, specificity, and predictive values were calculated. An exact McNemar test and generalized estimating equations from a binary logistic regression model were used to assess the difference in detection rates between modalities. A two-sided p value <0.05 was considered significant. Results: 100 patients were included. Sixty-five (65%) patients had follow-up DWI confirmation of acute infarct. NCCT revealed 17 (26.2%) acute infarcts without false positives. CTP revealed 42 (64.6%) acute infarcts with one false positive. Of the 23 infarcts missed on CTP, 10 (43.5%) were outside the volume of coverage while the remaining 13 (56.5%) were small cortical or lacunar type infarcts (≤15 mm in size). CTP was significantly more sensitive (64.6 vs. 26.2%, p < 0.0001) and accurate (76.0 vs. 52%, p < 0.0001) and had a better negative predictive value (59.6 vs. 42.2%, p = 0.032) than NCCT. Conclusion: In a retrospective cohort of 100 patients with symptoms of hyperacute stroke in the 3-hour window, CTP provided improved sensitivity and accuracy over NCCT.

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Perfusion-CT assessment of infarct core and penumbra: receiver operating characteristic curve analysis in 130 patients suspected of acute hemispheric stroke.

Max Wintermark, Adam Flanders, Birgitta K. Velthuis … (2006)

Different definitions have been proposed to define the ischemic penumbra from perfusion-CT (PCT) data, based on parameters and thresholds tested only in small pilot studies. The purpose of this study was to perform a systematic evaluation of all PCT parameters (cerebral blood flow, volume [CBV], mean transit time [MTT], time-to-peak) in a large series of acute stroke patients, to determine which (combination of) parameters most accurately predicts infarct and penumbra. One hundred and thirty patients with symptoms suggesting hemispheric stroke < or =12 hours from onset were enrolled in a prospective multicenter trial. They all underwent admission PCT and follow-up diffusion-weighted imaging/fluid-attenuated inversion recovery (DWI/FLAIR); 25 patients also underwent admission DWI/FLAIR. PCT maps were assessed for absolute and relative reduced CBV, reduced cerebral blood flow, increased MTT, and increased time-to-peak. Receiver-operating characteristic curve analysis was performed to determine the most accurate PCT parameter, and the optimal threshold for each parameter, using DWI/FLAIR as the gold standard. The PCT parameter that most accurately describes the tissue at risk of infarction in case of persistent arterial occlusion is the relative MTT (area under the curve=0.962), with an optimal threshold of 145%. The PCT parameter that most accurately describes the infarct core on admission is the absolute CBV (area under the curve=0.927), with an optimal threshold at 2.0 ml x 100 g(-1). In a large series of 130 patients, the optimal approach to define the infarct and the penumbra is a combined approach using 2 PCT parameters: relative MTT and absolute CBV, with dedicated thresholds.

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Why are stroke patients excluded from TPA therapy? An analysis of patient eligibility.

P A Barber, J ZHANG, A M Demchuk … (2001)

Thrombolytic therapy for acute stroke (<3 hours) will not have a major impact on death and dependency unless it is accessible to more patients. To determine why patients with ischemic stroke did not receive IV TPA and assess the availability of this therapy to patients with ischemic stroke. Consecutive patients with acute ischemic stroke were prospectively identified at a university teaching hospital between October 1996 and December 1999. Additional patients with ischemic stroke were identified that were admitted to one of three other hospitals in the Calgary region during the study period. The Oxford Community Stroke Programme Classification was used to record type and side of stroke. Of 2165 stroke patients presenting to the university hospital, 1168 (53.9%) were diagnosed with ischemic stroke, 31.8% with intracranial hemorrhage (intracerebral, subarachnoid, or subdural), and 13.9% with TIA. Delay in presentation to emergency department beyond 3 hours excluded 73.1% (854/1168). Major reasons for delay included uncertain time of onset (24.2%), patients waited to see if symptoms would improve (29%), delay caused by transfer from an outlying hospital (8.9%), and inaccessibility of treating hospital (5.7%). Twenty-seven percent of patients with ischemic stroke (314/1168) were admitted within 3 hours of sympton onset and of these 84 (26.7%) patients received IV TPA. The major reasons for exclusion in this group of patients (<3 hours) were mild stroke (13.1%), clinical improvement (18.2%), perceived protocol exclusions (13.6%), emergency department referral delay (8.9%), and significant comorbidity (8.3%). Of those patients who were considered too mild or were documented to have had significant improvement, 32% either remained dependent at hospital discharge or died during hospital admission. Throughout the region there was a total of 1806 ischemic stroke patients (admitted to all four Calgary hospitals). During this study period, 4.7% received IV TPA. The majority of patients are unable to receive TPA for acute ischemic stroke because they do no not reach the hospital soon enough. Of those patients presenting within 3 hours, 27% received the therapy but a further 31% were excluded because their symptoms were either considered too mild or were rapidly improving. Subsequently, a third of these patients were left either dependent or dead, bringing into question the initial decision not to treat.

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Early signs of brain infarction at CT: observer reliability and outcome after thrombolytic treatment--systematic review.

Joanna M. Wardlaw, Orell Mielke (2005)

To review systematically all reported early computed tomographic (CT) signs in acute ischemic stroke to determine interobserver agreement and the relationship between early CT signs and patient outcome with or without thrombolysis. A systematic review of the literature was conducted by using Cochrane Stroke Group methodology to identify studies published between 1990 and 2003 that were performed to assess interobserver agreement about early signs of infarction on CT scans obtained within 6 hours after onset of stroke symptoms and determine the relation of early signs of infarction to clinical outcome, including any interactive effect of thrombolysis. Interobserver agreement was measured with the kappa statistic, sensitivity, and specificity. The relation of early signs to clinical outcome with or without thrombolysis was assessed with calculated odds ratios and 95% confidence intervals. In 15 studies of interobserver agreement (median of 30 CT scans and six raters), the prevalence of all early infarction signs was 61% +/- 21 (standard deviation). Interobserver agreement (kappa statistics) ranged from 0.14 to 0.78 for any early infarction sign. The mean sensitivity and specificity for detection of early infarction signs with CT were 66% (range, 20%-87%) and 87% (range, 56%-100%), respectively. Experience improved detection, but knowledge of symptoms did not. In 15 studies of early infarction signs and outcome (including seven thrombolysis trials) in 3468 patients, any early infarction sign increased the risk of poor outcome (odds ratio, 3.11; 95% confidence interval: 2.77, 3.49). Two studies that sought interaction between early infarction signs and thrombolysis found no evidence that thrombolysis given in the presence of early infarction signs resulted in worse outcome than that due to early signs alone. Further work is required to determine which signs are most reliably detected, whether scoring systems help to improve detection, and whether any early infarction sign should influence decisions concerning thrombolysis. (c) RSNA, 2005.

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Journal

Journal ID (publisher-id): CED

Journal ID (nlm-ta): Cerebrovasc Dis

Journal ID (doi): 10.1159/issn.1015-9770

Title: Cerebrovascular Diseases

Publisher: S. Karger AG

ISSN (Print): 1015-9770

ISSN (Electronic): 1421-9786

Publication date Subscription-year: 2009

Publication date (Print): June 2009

Publication date (Electronic): 20 May 2009

Volume: 28

Issue: 1

Pages: 72-79

Affiliations

Departments of ^aRadiology and ^bNeurology, New York University Langone Medical Center, New York, N.Y., USA

Article

Publisher ID: 219300 Other ID: Cerebrovasc Dis 2009;28:72–79

DOI: 10.1159/000219300

PubMed ID: 19468218

SO-VID: 74e78fed-cf37-4a2d-a4cd-6f83c6adc484

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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

History

Date received : 27 October 2008

Date accepted : 02 March 2009

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Figures: 3, Tables: 2, References: 30, Pages: 8

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Perfusion CT Improves Diagnostic Accuracy for Hyperacute Ischemic Stroke in the 3-Hour Window: Study of 100 Patients with Diffusion MRI Confirmation

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Karger: Neurology and Neuroscience

Most cited references 16

Perfusion-CT assessment of infarct core and penumbra: receiver operating characteristic curve analysis in 130 patients suspected of acute hemispheric stroke.

Why are stroke patients excluded from TPA therapy? An analysis of patient eligibility.

Early signs of brain infarction at CT: observer reliability and outcome after thrombolytic treatment--systematic review.

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