Sensitivity of Non‐contrast
Computed Tomography
Net Water Uptake Versus
FLAIR
‐
MRI
, with
Gabriel Broocks, Andre Kemmling, Rene Werner, Thilo Sentker, Robert W. Regenhardt, Tobias Faizy, Anthony Kam, Rajiv Gupta, Helge Kniep, Lukas Meyer, Jens Fiehler, Karsten Alfke, Michael H. Lev Objective
On non‐contrast computed tomography (NCCT), progressive hypoattenuation can be quantified as percent net water uptake (%NWU), whereas relative fluid attenuated inversion recovery (rFLAIR)‐magnetic resonance imaging hyperintensity marks later‐stage vasogenic edema and blood–brain‐barrier disruption. We compared the degree and rate of %NWU versus rFLAIR development and characterized 4 ischemic edema imaging profiles relative to a magnetic resonance (MR)‐diffusion‐weighted‐imaging (MR‐DWI) reference standard.
Methods
NCCT and fluid attenuated inversion recovery (FLAIR) images from MR‐DWI‐positive hyperacute stroke patients were visually rated positive (+) or negative (−) for ischemic hypodensity/hyperintensity and sulcal‐effacement (SE), defining 4 edema imaging profiles: (I) NWU−/FLAIR−/SE−, (II) NWU+/FLAIR−/SE−, (III) NWU+/FLAIR+/SE−, and (IV) NWU+/FLAIR+/SE+. %NWU, rFLAIR, and relative apparent diffusion coefficient (rADC) were quantified within the DWI/apparent diffusion coefficient‐defined core region‐of‐interest, normalized to the contralateral mirror region, and compared between groups.
Results
Of 53 DWI+ patients, n = 5/17/13/17 were in groups I to IV, with mean onset‐to‐CT times of 2.4 ± 1.2/2.5 ± 1.6/3.2 ± 1.9/5.0 ± 1.6 hours ( p < 0.01), and baseline characteristics were comparable (all p ≥ 0.12). Mean %NWU differed between all groups (1.4 ± 0.3/4.3 ± 4.2/8.0 ± 4.1/13.6 ± 4.3; all pairwise p < 0.012), rADC did not ( p = 0.21), and rFLAIR differed only between groups II and III versus group IV ( p = 0.02, p = 0.04). %NWU and rFLAIR were uncorrelated ( R 2 = 0.02, p = 0.48). Fitted %NWU increased monotonically and near‐linearly within 4.5 hours post‐ictus, whereas rFLAIR rose abruptly only in the late transition to group IV.
Interpretation
Quantitative %NWU‐CT was more sensitive than rFLAIR for detecting the earliest edematous stages of hyperacute stroke, discriminating early, intermediate, late, and late‐severe (SE) stages; rFLAIR increased only in the latest stage. %NWU may, therefore, provide a practical, quantitative CT marker of edema progression, supporting acute triage and risk phenotyping in CT‐first pathways, pending prospective validation. ANN NEUROL 2026