Artifact Correction of Clinical Diffusion Weighted Imaging in Acute Ischemic Stroke

ABSTRACT Background Susceptibility‐induced geometric distortions and non‐physiologic hyperintensities confound acute ischemic stroke diagnosis on diffusion weighted imaging (DWI). Reverse phase‐encoded imaging needed for artifact correction is rarely acquired acutely. Structural imaging‐based correction is validated in healthy subjects, but its efficacy in acute stroke remains unclear. Purpose To investigate whether structural imaging‐based artifact correction reduces DWI distortions and non‐physiologic hyperintensities in clinical acute stroke imaging. Study Type Retrospective. Population 214 patients with acute ischemic stroke and clinical MRI from two centers. Field Strength/Sequences 1.5 T/3 T; single‐shot echo planar DWI; 3D MP‐RAGE and 2D spin echo, gradient echo, turbo spin echo, and turbo inversion recovery T1‐weighted sequences; 2D turbo spin echo and BLADE FLAIR sequences. Assessment DWI distortions were corrected using the Synb0‐DisCo and TOPUP algorithms with b0 and T1‐weighted images. Mutual information evaluated geometric agreement against FLAIR and T1‐weighted images before and after correction. The diagnostic value of hyperintense DWI lesions for apparent diffusion coefficient (ADC)‐defined reference infarct was assessed. Statistical Tests Wilcoxon sign rank or rank sum tests of mutual information, sensitivity, specificity, and positive and negative predictive value; Bland–Altman plots; and linear regression with coefficients of determination ( R 2 ) in linear and log space. Bonferroni‐adjusted p < 0.05 was significant. Results After correction, DWI demonstrated significantly increased mutual information against FLAIR images [0.31 (IQR, 0.25–0.38) versus 0.30 (0.24–0.35)] and T1‐weighted images [0.32 (IQR, 0.29–0.36) versus 0.29 (0.24–0.33)]. ADC‐defined infarct volumes before and after correction correlated strongly ( R 2 0.998, log 0.541) with a negative bias of 0.51 (95% CI, 0.18–0.85) mL. DWI hyperintensities before and after correction correlated strongly ( R 2 0.996, log 0.360) but demonstrated a negative bias of 2.47 (95% CI, 1.95–3.00) mL. After correction, DWI hyperintensities demonstrated significantly improved specificity [0.998 (IQR, 0.994–1.000) versus 0.997 (0.992–0.999)] and positive predictive value [0.53 (IQR, 0.31–0.77) versus 0.39 (0.16–0.63)] for ADC‐defined infarct. Data Conclusion Structural imaging‐based distortion correction of routinely acquired clinical DWI in acute ischemic stroke improves anatomic geometry and reduces false positive hyperintensities. Evidence Level 3. Stage of Technical Efficacy 3.