DWI Intensity Values Predict FLAIR Lesions in Acute Ischemic Stroke

Abstract

Background and PurposeIn acute stroke, the DWI-FLAIR mismatch allows for the allocation of patients to the thrombolysis window (<4.5 hours). FLAIR-lesions, however, may be challenging to assess. In comparison, DWI may be a useful bio-marker owing to high lesion contrast. We investigated the performance of a relative DWI signal intensity (rSI) threshold to predict the presence of FLAIR-lesions in acute stroke and analyzed its association with time-from-stroke-onset.MethodsIn a retrospective, dual-center MR-imaging study we included patients with acute stroke and time-from-stroke-onset ≤12 hours (group A: n = 49, 1.5T; group B: n = 48, 3T). DW- and FLAIR-images were coregistered. The largest lesion extent in DWI defined the slice for further analysis. FLAIR-lesions were identified by 3 raters, delineated as regions-of-interest (ROIs) and copied on the DW-images. Circular ROIs were placed within the DWI-lesion and labeled according to the FLAIR-pattern (FLAIR+ or FLAIR−). ROI-values were normalized to the unaffected hemisphere. Adjusted and nonadjusted receiver-operating-characteristics (ROC) curve analysis on patient level was performed to analyze the ability of a DWI- and ADC-rSI threshold to predict the presence of FLAIR-lesions. Spearman correlation and adjusted linear regression analysis was performed to assess the relationship between DWI-intensity and time-from-stroke-onset.ResultsDWI-rSI performed well in predicting lesions in FLAIR-imaging (mean area under the curve (AUC): group A: 0.84; group B: 0.85). An optimal mean DWI-rSI threshold was identified (A: 162%; B: 161%). ADC-maps performed worse (mean AUC: A: 0.58; B: 0.77). Adjusted regression models confirmed the superior performance of DWI-rSI. Correlation coefficents and linear regression showed a good association with time-from-stroke-onset for DWI-rSI, but not for ADC-rSI.ConclusionAn easily assessable DWI-rSI threshold identifies the presence of lesions in FLAIR-imaging with good accuracy and is associated with time-from-stroke-onset in acute stroke. This finding underlines the potential of a DWI-rSI threshold as a marker of lesion age.

Stroke onset time estimation from multispectral quantitative magnetic resonance imaging in a rat model of focal permanent cerebral ischemia

“…Animals were scanned at 9.4T for qT 1 , qT 2 (15). This early ADC decrease is attributed to energy failure and cytotoxic oedema (7,8) and is often assumed to represent the irreversibly infarcted core (11), however preclinical (12) and clinical (13) studies suggest greater complexity.…”

Does b1000–b0 Mismatch Challenge Diffusion-Weighted Imaging–Fluid Attenuated Inversion Recovery Mismatch in Stroke?

“…2 Diffusionweighted imaging (DWI)/fluid-attenuated inversion recovery (FLAIR) mismatch has been proposed for magnetic resonance imaging (MRI) estimation of lesion age in acute stroke 3 but still presents some drawbacks. [4][5][6][7][8] To circumvent the subjectivity of the visual rating of images using this method, different approaches have been proposed with conflicting results, 4,6,[8][9][10][11][12] and further studies are needed to verify their utility.…”

Prediction of Stroke Onset Is Improved by Relative Fluid-Attenuated Inversion Recovery and Perfusion Imaging Compared to the Visual Diffusion-Weighted Imaging/Fluid-Attenuated Inversion Recovery Mismatch

“…8,9 In addition, relative DWI intensities could approximate but not improve the predictive value of the DWI/FLAIR mismatch. 16,17 In our study, the voxel-based relative FLAIR technique did result in a small improvement of the prediction of time for symptom onset. In a sensitivity analysis, a nonvoxel-based approach to calculate rFLAIR was performed, which showed a less robust improvement in time prediction compared with the voxel-based analysis.…”