T reatment of patients with acute ischemic stroke (AIS) is aimed at reopening occluded arteries and reestablishment of intracranial perfusion. Determining pivotal characteristics about the occluding thrombus using available imaging has the potential to improve patient's diagnostics and prognostics.Background and Purpose-Preclinical studies showed that thrombi can be permeable and may, therefore, allow for residual blood flow in occluded arteries of patients having acute ischemic stroke. This perviousness may increase tissue oxygenation, improve thrombus dissolution, and augment intra-arterial treatment success. We hypothesize that the combination of computed tomographic angiography and noncontrast computed tomography imaging allows measurement of contrast agent penetrating a permeable thrombus, and it is associated with improved outcome. Methods-Thrombus and contralateral artery attenuations in noncontrast computed tomography and computed tomographic angiography images were measured in 184 Multicenter Randomized Clinical trial of Endovascular treatment of acute ischemic stroke in the Netherlands (MR CLEAN) patients with thin-slice images. Two quantitative estimators of the thrombus permeability were introduced: computed tomographic angiography attenuation increase (Δ) and thrombus void fraction (ε). Patients were dichotomized as having a pervious or impervious thrombus and associated with outcome, recanalization, and final infarct volume. Results-Patients with Δ≥10.9 HU (n=81 [44%]) and ε≥6.5% (n=77 [42%]) were classified as having a pervious thrombus.These patients were 3.2 (95% confidence interval, 1.7-6.4) times more likely to have a favorable outcome, and 2.5 (95% confidence interval, 1.3-4.8) times more likely to recanalyze, for Δ based classification, and similarly for ε. These odds ratios were independent from intravenous or intra-arterial treatment. Final infarct volume was negatively correlated with both perviousness estimates (correlation coefficient, −0.39 for Δ and −0.40 for ε).
Conclusions-This
on behalf of the MR CLEAN investigators ABSTRACT BACKGROUND AND PURPOSE: Thrombus CT characteristics might be useful for patient selection for intra-arterial treatment. Our objective was to study the association of thrombus CT characteristics with outcome and treatment effect in patients with acute ischemic stroke.
IntroductionThrombus density may be a predictor for acute ischemic stroke treatment success. However, only limited data on observer variability for thrombus density measurements exist. This study assesses the variability and bias of four common thrombus density measurement methods by expert and non-expert observers.MethodsFor 132 consecutive patients with acute ischemic stroke, three experts and two trained observers determined thrombus density by placing three standardized regions of interest (ROIs) in the thrombus and corresponding contralateral arterial segment. Subsequently, absolute and relative thrombus densities were determined using either one or three ROIs. Intraclass correlation coefficient (ICC) was determined, and Bland–Altman analysis was performed to evaluate interobserver and intermethod agreement. Accuracy of the trained observer was evaluated with a reference expert observer using the same statistical analysis.ResultsThe highest interobserver agreement was obtained for absolute thrombus measurements using three ROIs (ICCs ranging from 0.54 to 0.91). In general, interobserver agreement was lower for relative measurements, and for using one instead of three ROIs. Interobserver agreement of trained non-experts and experts was similar. Accuracy of the trained observer measurements was comparable to the expert interobserver agreement and was better for absolute measurements and with three ROIs. The agreement between the one ROI and three ROI methods was good.ConclusionAbsolute thrombus density measurement has superior interobserver agreement compared to relative density measurement. Interobserver variation is smaller when multiple ROIs are used. Trained non-expert observers can accurately and reproducibly assess absolute thrombus densities using three ROIs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00234-015-1607-4) contains supplementary material, which is available to authorized users.
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