Spectroscopic magnetic resonance imaging using spiral trajectories

Abstract

Disclosed is a rapid data acquisition method that applies spiral-based k-space trajectories to spectroscopic imaging. In contrast to conventional acquisition methods, this technique offers independent control over imaging time and spatial resolution. The rapid scan enables the acquisition of spectroscopic data from three spatial dimensions in the same time that conventional methods acquire a single slice. This three-dimensional acquisition delivers an order of magnitude more data than the conventional methods, with no loss in SNR. In addition to three-dimensional spectroscopic imaging, other applications of the rapid k-space scanning with spiral trajectories are described. Sophisticated acquisition methods based on multiple-quantum editing can be incorporated into spectroscopic imaging sequences without a loss in SNR. These editing methods have shown particular promise in the detection of the important lactate signal in the presence of strong, undesired lipid signals. More generally, any combination of RF and gradient waveforms can precede the spectroscopic readout, as long as it excites transverse magnetization for the desired metabolites and suppresses the undesired water and lipid resonances. Rapid scans to acquire chemical-shift inhomogeneity information are also described, where a separate acquisition of the water and lipid signal is used to collect a robust and reliable map of the main field inhomogeneities.