3T-versus-7T DTI with 36 diffusion-encoding directions at b = 3000 s/mm2 and 2.0 × 2.0 × 2.0 mm isotropic voxel resolution. 3T-versus-7T DTI with 36 diffusion-encoding.

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3T-versus-7T DTI with 36 diffusion-encoding directions at b = 3000 s/mm2 and 2.0 × 2.0 × 2.0 mm isotropic voxel resolution. 3T-versus-7T DTI with 36 diffusion-encoding directions at b = 3000 s/mm2 and 2.0 × 2.0 × 2.0 mm isotropic voxel resolution. Directionally encoded color FA maps at the axial level of cingulum bundles and the callosal striations are shown for 3T (A) and for 7T (B) in a healthy adult volunteer. Both scanners were equipped with 40 mT/m gradients and 8-channel phased-array head coils, and ASSET parallel imaging was used with an acceleration factor of 2. The standard DTI color conventions are used, with red representing left-right fiber orientation, green representing anteroposterior, and blue representing craniocaudal. With this combination of high spatial resolution and very strong diffusion weighting, the 3T image appears grainy because of inadequate SNR. However, with identical scanning parameters, the additional SNR at 7T produces a higher quality image. Parallel imaging is essential for SS-EPI at ultra-high field to combat the increased susceptibility artifacts as well as the signal intensity loss and contrast blurring due to shorter T2 ad T2* relaxation times. P. Mukherjee et al. AJNR Am J Neuroradiol 2008;29:843-852 ©2008 by American Society of Neuroradiology