title: (31) P MR spectroscopic imaging of the human prostate at 7 T: T1 relaxation times, Nuclear Overhauser Effect, and spectral characterization.
abstract: OBJECTIVE
  Optimization of phosphorus ((31) P) MR spectroscopic imaging (MRSI) of the human prostate at 7 T by the evaluation of T1 relaxation times and the Nuclear Overhauser Effect (NOE) of phosphorus-containing metabolites.
  
  
  METHODS
  Twelve patients with prostate cancer and one healthy volunteer were scanned on a 7 T whole-body system using a (31) P endorectal coil combined with an eight-channel (1) H body array coil. T1 relaxation times were measured using progressive saturation in a two-dimensional localization sequence. (31) P MRSI was performed twice: once without NOE and once with NOE using low-power continuous wave (1) H irradiation to determine NOE enhancements.
  
  
  RESULTS
  T1 relaxation times of (31) P metabolites in the human prostate at 7 T varied between 3.0 and 8.3 s. Positive but variable NOE enhancements were measured for most metabolites. Remarkably, the (31) P MR spectra showed two peaks in chemical shift range of inorganic phosphate.
  
  
  CONCLUSIONS
  Knowledge of T1 relaxation times and NOE enhancements enables protocol optimization for (31) P MRSI of the prostate at 7 T. With a strongly reduced (31) P flip angle (≤ 45°), a (31) P MRSI dataset with optimal signal-to-noise ratio per unit time can be obtained within 15 minutes. The NOE enhancement can improve fitting accuracy, but its variability requires further investigation.
authors.affiliation: Department of Radiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Miriam W
authors.initials: MW
authors.lastname: Lagemaat
authors.forename: Marnix C
authors.initials: MC
authors.lastname: Maas
authors.forename: Eline K
authors.initials: EK
authors.lastname: Vos
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Bitz
authors.forename: Stephan
authors.initials: S
authors.lastname: Orzada
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiland
authors.forename: Mark J
authors.initials: MJ
authors.lastname: van Uden
authors.forename: Thiele
authors.initials: T
authors.lastname: Kobus
authors.forename: Arend
authors.initials: A
authors.lastname: Heerschap
authors.forename: Tom W J
authors.initials: TW
authors.lastname: Scheenen
mesh_terms: D000368:Aged; D000465:Algorithms; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D057054:Molecular Imaging / Q000379:methods*; D017553:Phosphorus Compounds / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D011467:Prostate; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D017553:Phosphorus Compounds; D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals
keywords: 31P MR spectroscopic imaging; 7 Tesla; magnetic field strength; Nuclear Overhauser Effect; T1 relaxation; prostate