Removal of local field gradient artifacts in T2*-weighted images at high fields by gradient-echo slice excitation profile imaging
✍ Scribed by Qing X. Yang; Gerald D. Williams; Roger J. Demeure; Timothy J. Mosher; Michael B. Smith
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 891 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
Development of high magnetic field MRI techniques is hampered by the significant artifacts produced by B~0~ field inhomogeneities in the excited slices. A technique, gradient‐echo slice excitation profile imaging (GESEPI), is presented for recovering the signal lost caused by intravoxel phase dispersion in T~2~*‐weighted images. This technique superimposes an incremental gradient offset on the slice refocusing gradient to sample Jr‐space over the full range of spatial frequencies of the excitation profile. A third Fourier transform of the initial two‐dimensional image set generates an image set in which the artifacts produced by the low‐order B~0~ inhomogeneity field gradients in the sample are separated and removed from the high‐order microscopic field gradients responsible for T~2~* contrast. Application to high field brain imaging, at 3.0 T for human and at 9.4 T for immature rat imaging demonstrates the significant improvement in quality of the T~2~*‐weighted contrast images.