Abstract
PurposeCT attenuation of ischemic brain reduces with time after stroke onset. We aimed to quantify this relationship and test the feasibility and accuracy of estimating stroke onset time using only CT attenuation of visible ischemic lesions, the CT-Clock Tool.MethodsWe selected CT scans with ischemic lesions representing a range of stroke-onset-to-scan times (elapsed time) from a well-defined stroke trial. We measured the attenuation of ischemic lesions and contralateral normal brain to derive attenuation ratio. We assigned scans to development (75%) or test (25%) datasets. We plotted the relationship between attenuation ratio and elapsed time in the development dataset and derived a best-fit curve. We calculated estimated time in the test dataset using only the attenuation ratio curve. We compared estimated time to elapsed time and derived absolute error for estimated time. We assessed area under the receiver operating characteristic (AUROC) curve for identifying scans ≤ 4.5 h elapsed time.ResultsWe included 342 scans from 200 patients (41% male, median age 83 years). Elapsed time range: 22 min to 36 days. Estimation errors were least at early elapsed times (r = 0.82, p < 0.0001): median absolute error was 23, 106, 1030 and 1933 min for scans acquired ≤ 3, > 3–9, > 9–30 and > 30 h from stroke onset, respectively. AUROC was high at 0.955.ConclusionsIt is feasible to accurately estimate stroke onset time using simple attenuation measures of ischemic brain. Our method was most accurate 0–9 h from onset and may be useful for treatment eligibility assessment, especially where imaging resources are limited.
Highlights
In the first hours and days following the onset of an ischemic stroke, the CT attenuation of affected brain reduces with time
Adult patients with acute stroke of any severity and no upper age limit were eligible if stroke onset time was clearly determined and treatment started within 6 h of onset, and baseline brain imaging had excluded haemorrhage and structural stroke mimics
We provide evidence that it is possible, with high accuracy and reasonable precision, to estimate time from ischemic stroke onset using simple CT brain attenuation measurements alone, during the early, most clinically relevant period
Summary
We aimed to quantify this relationship and test the feasibility and accuracy of estimating stroke onset time using only CT attenuation of visible ischemic lesions, the CT-Clock Tool. The aims of our project were first to precisely quantify the relationship between non-enhanced CT attenuation of ischemic brain lesions and time using well-defined stroke trial data and second to test whether it is feasible to use only the CT attenuation of ischemic lesions to accurately estimate time of stroke onset for individual patients, the CT-Clock Tool. For efficient spread of data points, we aimed to include a maximum of the following: one scan for each of the 360 min from 0 to 6 h; one scan for every 10 min window from 6 to 12 h; one scan for every 30 min window from 12 to 48 h; one scan per hour from days 3–7; and any scans from later time points
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