title: Correction of frequency drifts induced by gradient heating in 1H spectra using interleaved reference spectroscopy.
abstract: OBJECTIVE
  To evaluate the impact of heating-induced frequency drifts on single-voxel spectroscopy and to demonstrate correction strategies based on the interleaved reference scan technique.
  
  
  METHODS
  Frequency drifts induced by gradient heating are assessed for two clinical 3 Tesla (T) whole body MR systems. The interleaved reference scan (IRS) method is used for correcting these frequency drifts in 1H spectra in vitro and in vivo. For severely drift-affected spectroscopy experiments, a feedback-based version of the IRS sequence is proposed, which adds the functionality of a frequency lock to prevent a degradation of the water suppression.
  
  
  RESULTS
  It is shown that the line widths of the spectral resonances can be largely reduced with the interleaved reference scan method, resulting in considerably improved peak resolution and signal-to-noise ratio. The feedback-based IRS method additionally allows for stable water suppression, even in the presence of very strong frequency drifts.
  
  
  CONCLUSIONS
  If spectroscopy scans are combined with imaging scans with a high gradient duty cycle such as diffusion-weighted imaging or functional MRI, a drift correction with IRS can considerably improve the validity of data analysis in research studies.
authors.affiliation: Department of Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany. thomas.lange@uniklinik-freiburg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Lange
authors.forename: Maxim
authors.initials: M
authors.lastname: Zaitsev
authors.forename: Martin
authors.initials: M
authors.lastname: Buechert
mesh_terms: D000465:Algorithms; D003627:Data Interpretation, Statistical; D003952:Diagnostic Imaging / Q000379:methods; D006358:Hot Temperature; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012016:Reference Values; D015203:Reproducibility of Results; D013053:Spectrophotometry / Q000379:methods; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water