title: Volumetric spectroscopic imaging with spiral-based k-space trajectories.
abstract: Spiral-based k-space trajectories were applied in a spectroscopic imaging sequence with time-varying readout gradients to collect volumetric chemical shift information. In addition to spectroscopic imaging of low signal-to-noise ratio (SNR) brain metabolites, the spiral trajectories were used to rapidly collect reference signals from the high SNR water signal to automatically phase the spectra and to aid the reconstruction of metabolite maps. Spectral-spatial pulses were used for excitation and water suppression. The pulses were designed to achieve stable phase profiles in the presence of up to 20% variation in the radiofrequency field. A gridding algorithm was used to resample the data onto a rectilinear grid before fast Fourier transforms. This method was demonstrated by in vivo imaging of brain metabolites at 1.5 T with 10 slices of 18 x 18 pixels each. Nominal voxel size was 1.1 cc, spectral bandwidth was 400 Hz, scan time was 18 min for the metabolite scan and 3 min for the reference scan.
authors.affiliation: Department of Radiology, Stanford University, California, USA.
authors.forename: E
authors.initials: E
authors.lastname: Adalsteinsson
authors.forename: P
authors.initials: P
authors.lastname: Irarrazabal
authors.forename: S
authors.initials: S
authors.lastname: Topp
authors.forename: C
authors.initials: C
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Macovski
authors.forename: D M
authors.initials: DM
authors.lastname: Spielman
mesh_terms: D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D055592:Biophysical Phenomena; D001703:Biophysics; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology*; D001931:Brain Mapping / Q000295:instrumentation; D002794:Choline / Q000378:metabolism; D003199:Computer Systems; D003401:Creatine / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D012016:Reference Values
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate; D003401:Creatine; D002794:Choline