title: 2D AMESING multi-echo (31)P-MRSI of the liver at 7T allows transverse relaxation assessment and T2-weighted averaging for improved SNR.
abstract: OBJECTIVE
  Liver diseases are a major global health concern often requiring invasive assessment by needle biopsy. (31)P magnetic resonance spectroscopic imaging (MRSI) allows non-invasive probing of important liver metabolites. Recently, the adiabatic multi-echo spectroscopic imaging sequence with spherical k-space sampling (AMESING) was introduced at 7T, enabling acquisition of T2 information. T2-weighed averaging of the multiple echoes improves signal-to-noise ratio (SNR). The purpose of our study was to implement AMESING MRSI of the liver at 3T and 7T, derive localized T2 information and compare T2-weighted average spectra in terms of SNR.
  
  
  METHODS
  Ten male volunteers underwent 2D AMESING MRSI at 3T and 7T after a minimum four-hour fast. SNR was calculated for PC, PE, Pi, GPE, GPC and α-ATP using maximum peak amplitudes and the SD of the noise. Metabolite peak ratios were calculated after fitting in jMRUI. SNR values and peak ratios were compared with the Wilcoxon signed-rank test.
  
  
  RESULTS
  For the first time liver metabolites' T2 values at 7T were measured: PE (55.6±3.5 ms), PC (51.2±2.3 ms), Pi (46.4±1.1 ms), GPE (44.0±0.8 ms), GPC (50.4±0.8 ms) and α-ATP (18.2±0.4 ms). SNR gain using T2-weighted averaging at 7T resulted in a 1.2× SNR gain. In conjunction with higher field strength and improved coil set-up T2-weighted averaging at 7T allowed a total 3.2× SNR gain compared to 3T FID-only.
  
  
  CONCLUSIONS
  AMESING 2D MRSI of the liver at 7T provides T2 values that allow T2-weighted averaging of data from multiple echoes resulting in improved SNR.
authors.affiliation: Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: j.h.runge@amc.uva.nl.
authors.forename: Jurgen Henk
authors.initials: JH
authors.lastname: Runge
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Wybe J M
authors.initials: WJ
authors.lastname: van der Kemp
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Dennis W J
authors.initials: DW
authors.lastname: Klomp
authors.affiliation: Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.affiliation: Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Aart J
authors.initials: AJ
authors.lastname: Nederveen
authors.affiliation: Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Stoker
mesh_terms: D000328:Adult; D000465:Algorithms; D016477:Artifacts; D015415:Biomarkers / Q000378:metabolism; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008099:Liver / Q000033:anatomy & histology* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D017553:Phosphorus Compounds / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D017553:Phosphorus Compounds; D010759:Phosphorus Isotopes
keywords: (31)P; 7T; Liver; Magnetic resonance spectroscopy; Phosphorus; Quantification