Reliability of a Semi-Automated Technique of Cerebral Infarct Volume Measurement with CT

Abstract

Background: A reliable method of infarct volume measurement is needed if infarct volume is to be used as an outcome measure in clinical stroke trials. We investigated the reproducibility of a semi-automated method of computed tomography (CT) infarct volume measurement amongst three stroke research fellows with no formal neuroradiology training and two consultant neuroradiologists. Methods: CT brain scans for volumetric analysis were performed at 5 to 7 days in 34 patients with acute ischaemic stroke, of which 28 scans showed visible recent infarction. Five observers independently traced the infarct boundary on digitised images with a cursor. Volumetric analysis incorporated pixel thresholding with preset Hounsfield thresholds. One of the observers repeated the analyses on 21 of the scans in order to assess intraobserver variation. Results: Median infarct volume was 35.7 cm³ (range 0.2–318 cm³). The closest limits of observed agreement (mean ± 1.96 SD) between pairs of observers were between a research fellow and neuroradiologist (–29 to 21 cm³). The widest limits of agreement were between a different research fellow and the same neuroradiologist (–39.1 to 41.4 cm³). The limits of agreement between infarct volumes measured on two separate occasions by one of the research fellows were –7 to 8 cm³. Conclusions: Intraobserver reliability of CT infarct volume measurements performed by a stroke research fellow was superior to interobserver reliability between any pair of observers. The wide limits of agreement between different observers using manual tracing may not be acceptable in multicentre trials of acute ischaemic stroke treatment, but volume measurement by a single observer appears to be more reliable.

Clinical outcome following acute ischaemic stroke relates to both activation and autoregulatory inhibition of cytokine production

“…Ischaemic stroke patients underwent a second CT brain scan at 5 to 7 days for determination of cerebral infarct volume, using a semi-automated technique [20]. Ankle brachial pressure index (ABPI) was used to classify degree of atherosclerosis where carotid duplex data were unavailable.…”

Variability of the systemic acute phase response after ischemic stroke

“…Plasma CRP and IL-6 were assayed using highsensitivity enzyme-linked immunosorbent assays described elsewhere [6]. Computed tomography (CT) brain scans were performed within 24 h to exclude primary intracerebral haemorrhage or stroke mimic and repeated at 5 to 7 days for volumetric analysis using a semi-automated technique [8]. Stroke severity was assessed using the National Institutes of Health Stroke Scale (NIHSS) score [9] at presentation and 5 to 7 days.…”

Defining the Extent of Irreversible Brain Ischemia Using Perfusion Computed Tomography

“…Until this occurs, PCT will not become incorporated into the routine clinical paradigm for the assessment of acute stroke patients for thrombolytic therapy. The need for better acute stroke diagnostics and training [22] has become greater since it was recently shown that the current technique of perfusion-diffusion mismatch is not sufficient for the selection of patients to be treated with thrombolysis [23]. …”