Imaging at high magnetic fields: initial experiences at 4 T.


This article reviews the preliminary experiences and the results obtained on the human brain at 4 T at the University of Minnesota. Anatomical and functional images are presented. Contrary to initial expectations and the early results, it is possible to obtain high-resolution images of the human brain with exquisite T1 contrast, delineating structures especially in the basal ganglia and thalamus, which were not observed clearly in 1.5-T images until now. These 4-T images are possible using a new approach that achieves maximal contrast for different T1 values at approximately the same repetition time and has built-in tolerance to variations in B1 magnitude. For functional images, the high field provides increased contribution from the venuoles and the capillary bed because the susceptibility-induced alterations in 1/T2* from these small-diameter vessels increase quadratically with the magnitude of the main field. Images obtained with short echo times at 4 T, and by implication at lower fields with correspondingly longer echo times, are expected to be dominated by contributions from large venous vessel or in-flow effects from the large arteries; such images are undesirable because of their poor spatial correspondence with actual sites of neuronal activity.

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@article{Ugurbil1993ImagingAH, title={Imaging at high magnetic fields: initial experiences at 4 T.}, author={Kamil Ugurbil and Michael Garwood and Jutta Maria Ellermann and Klaus Hendrich and Richard Hinke and X Hu and Sang G. Kim and Ravi S. Menon and Hellmut Merkle and Satoshi Ogawa}, journal={Magnetic resonance quarterly}, year={1993}, volume={9 4}, pages={259-77} }