Observer variability of absolute and relative thrombus density measurements in patients with acute ischemic stroke

Abstract

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.

Value of Thrombus CT Characteristics in Patients with Acute Ischemic Stroke

“…However, a previous study showed that the density measurements by the trained observers were reproducible and showed very good agreement with those of the experienced radiologists. 27 In this study, multiple tests were performed without adjusting the P values. This choice could have resulted in a false significant association between thrombus characteristics and outcome measures or a false significant treatment-effect modification by the thrombus characteristics.…”

“…1 The length of the thrombus was measured on NCCT with the aid of coregistered CTA, with an inhouse-developed MeVisLab interface (www.mevislab.de). 15 A trained user (J.B., with 3 years of experience in neuroimaging research), blinded to clinical information, placed several seed points in the thrombus (Fig 1). Subsequently, the software determined the centerline through the thrombus.…”

“…With the same program, the DT was measured by placing several seed points starting in the ICA-T to the proximal border of the thrombus (Fig 2). The volume of the thrombus was calculated with a semiautomated segmentation method adapted from Santos et al 15 The centerline already determined for the length measurement was subsequently used in the volume calculation. Density measurement of the thrombus and contralateral vessel segment was performed on NCCT and coregistered CTA by a trained observer (M.d.B., with 1 year of experience), blinded to clinical information, with the in-house-developed MeVisLab interface.…”

Thrombus Permeability Is Associated With Improved Functional Outcome and Recanalization in Patients With Ischemic Stroke

“…Clinical outcome such as modified Rankin Scale (mRS), modified Arterial Occlusive Lesion (mAOL) score, Thrombolysis in Cerebral Infarction perfusion scale (TICI) score, and final infarct volume (FIV), 9 and baseline clinical characteristics (such as age, sex, National Institutes of Health Stroke Scale [NIHSS] score, time from onset to intravenous [IV] recombinant tissue-type plasminogen activator [r-tPA] treatment, time from onset to groin puncture, occlusion site, and atrial fibrillation) were collected during the execution of the trial. Of 248 consecutive patients with thin-slice NCCT and CTA, 10 were excluded because the time between NCCT and CTA imaging exceeded 30 minutes, 3 because CTA was performed before NCCT imaging, 3 because CTA and NCCT were performed on a different scanner, 39 because of imaging quality limitations, including movement artifacts (25), noisy NCCT image (10), incomplete region of interest (3), and CTA triggered too early or too late (1). Of the 193 remaining patients, imaging data of 9 patients were used for manual thrombus intensity signal measurement training.…”

“…10 In short, CTA images were automatically aligned with NCCT images using a rigid registration method. 11 The quality of the registration was assessed by visual inspection.…”