A comparison of images generated from diffusion‐weighted and diffusion‐tensor imaging data in hyper‐acute stroke

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Abstract
Purpose: To compare isotropic (combined diffusion‐weighted image [CMB], apparent diffusion coefficient [ADC], TRACE, exponential ADC [eADC], and isotropically‐weighted diffusion image [isoDWI]) and anisotropic (relative anisotropy [RA], fractional anisotropy [FA], and volume ratio [VR]) diffusion images collected with fast magnetic resonance (MR) diffusion‐weighted (DWI) and diffusion‐tensor (DTI) acquisition strategies (each less than one minute) in hyper‐acute stroke.Materials and Methods: Twenty‐one patients suffering from ischemic stroke—imaged within six hours of symptom onset using both DWI and DTI—were analyzed. Regions of interest were placed in the ischemic lesion and in normal contralateral tissue and the percent difference in image intensity was calculated for all nine generated images.Results: The average absolute percent changes for the isotropic strategies were all > 38%, with isoDWI found to have a difference of 50.7% ± 7.9% (mean ± standard error, P < 0.001). The ADC maps had the most significant difference (–42.4% ± 2.0%, P < 0.001, coefficient of variation = 0.22). No anisotropic images had significant differences.Conclusion: Anisotropic maps do not consistently show changes in the first six hours of ischemic stroke; therefore, isotropic maps, such as those obtained using DWI, are more appropriate for detecting hyper‐acute stroke. Anisotropic images, however, may be useful to differentiate hyper‐acute stroke from acute and sub‐acute stroke. J. Magn. Reson. Imaging 2004;20:193–200.