SNR gains with superconducting coils and hyperpolarized inert gas

Abstract

Magnetic resonance microscopy (MRM) has advanced from a technical challenge to a practical tool in a wide range of basic sciences (1). The nondestructive nature of the technique allows for repeated studies of the same sample, retrospective studies through any arbitrary plane, registered studies using different contrast mechanisms, and examination of valuable specimens. "Proton contrast" is provided by making use of T1, T2, T1ρ , diffusion, and magnetization contrast weightings, thus permitting direct examination of the state of water in tissues; something not possible with other microscopic techniques. The technical hurdles imposed by a limited signal-to-noise ratio (SNR) have been partially overcome by improved RF coil design and by three dimensional Fourier transform encoding for large arrays. We have introduced two additional technologies that help to further redress this SNR deficit: superconducting RF coils and inert gas hyperpolarization.It has been argued elsewhere (2,3) that the dominant source of noise in the receiving chain for small objects in high fields is the pickup coil and the preamplifier.