title: Detection and correction of frequency instabilities for volumetric 1H echo-planar spectroscopic imaging.
abstract: Spectral quality in 1H magnetic resonance spectroscopic imaging (MRSI) critically depends on the stability of the main magnetic field. For echo-planar MRSI implemented at 3 T, temperature variation in the passive steel shims of the magnet system can lead to a significant drift in the resonance frequency. A method is presented that incorporates interleaved measurement of the instantaneous resonance frequency of a reference water signal into a volumetric MRSI sequence and allows correction for the drift during postprocessing. Results from normal human brain at 3 T indicate that the correction largely removes lineshape distortions, recovers metabolite signal loss, and improves spectral quality by reducing the width of spectral lines; however, particularly in inferior regions, other sources of distortion may be present that cause broadening of spectral lines.
authors.affiliation: Department of Radiology, University of Miami School of Medicine, Miami, Florida, USA. ebel@itsa.ucsf.edu
authors.forename: Andreas
authors.initials: A
authors.lastname: Ebel
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Maudsley
mesh_terms: D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology* / Q000378:metabolism*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D018377:Neurotransmitter Agents / Q000378:metabolism; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D018377:Neurotransmitter Agents; D011522:Protons