Technology for Ultrahigh Field Imaging

Developments in ultrahigh field (UHF) magnets for human imaging are intricately tied to the use of magnetic resonance (MR) techniques to image alterations in human brain activity, i.e. functional brain mapping with magnetic resonance imaging (fMRI). The reason neuroimaging has been the main justification for the push to attain high magnetic fields resides in the difficult task we confront in studying the human brain. Concurrent efforts undertaken at the time to better understand the mechanisms underlying fMRI pointed to blood oxygenation level-dependent contrast improvements with magnetic fields, more so for weaker responses associated with the parenchyma as opposed to the undesirable signals arising from the draining veins. One of the primary motivations for going to ultrahigh magnetic fields despite the large escalation in cost associated with building such magnets is the field-dependent increases in signal-to-noise ratio. High performance gradients with high maximal gradient strength and high slew rates are also critical technologies for UHF MRI.