"In this work, we present the first human magnetic resonance image (MRI) obtained at ultra-high field strengths (8 Tesla). We demonstrate that clinical imaging will be possible at 8 Tesla and that reasonable quality head images can be obtained at this field strength. Most importantly, we emphasize that the power required to excite the spins at 8 Tesla is much lower that had been predicted by nuclear magnetic resonance theory. A 90O pulse in the head at 8 Tesla requires only ~0.085 Joules of energy (90 watts for a 2 lobe 4 msec sinc pulse). Based on measurements at 4 Tesla, 1-2 Joules of energy should have been utilized to achieve a 90O excitation at 8 Tesla. The fact that the energy required for spin excitation at 8 Tesla is much lower than predicted by NMR theory will be extremely important to the viability of ultra-high field imaging, since concerns related to power absorption and specific absorption rate (SAR) violations at ultra-high field are alleviated. As such, it will be possible to utilize RF intensive pulse sequences and adiabatic spin excitation at 8 Tesla without significant risk to the subject."
P.-M. L. Robitaille et. al. NMR Biomedicine 11, 263-265 (1998)