title: Water proton T1 measurements in brain tissue at 7, 3, and 1.5 T using IR-EPI, IR-TSE, and MPRAGE: results and optimization.
abstract: METHODS
  This paper presents methods of measuring the longitudinal relaxation time using inversion recovery turbo spin echo (IR-TSE) and magnetization-prepared rapid gradient echo (MPRAGE) sequences, comparing and optimizing these sequences, reporting T1 values for water protons measured from brain tissue at 1.5, 3, and 7 T. T1 was measured in cortical grey matter and white matter using the IR-TSE, MPRAGE, and inversion recovery echo planar imaging (IR-EPI) pulse sequences.
  
  
  RESULTS
  In four subjects the T1 of white and grey matter were found to be 646+/-32 and 1,197+/-134 ms at 1.5 T, 838+/-50 and 1,607+/-112 ms at 3T, and 1,126+/-97, and 1,939+/-149 ms at 7 T with the MPRAGE sequence. The T1 of the putamen was found to be 1,084+/-63 ms at 1.5 T, 1,332+/-68 ms at 3T, and 1,644+/-167 ms at 7 T. The T1 of the caudate head was found to be 1,109+/- 66 ms at 1.5 T, 1,395+/-49 ms at 3T, and 1,684+/-76 ms at 7 T.
  
  
  CONCLUSIONS
  There was a trend for the IR-TSE sequence to underestimate T1 in vivo. The sequence parameters for the IR-TSE and MPRAGE sequences were also optimized in terms of the signal-to-noise ratio (SNR) in the fitted T1. The optimal sequence for IR-TSE in terms of SNR in the fitted T1 was found to have five readouts at TIs of 120, 260, 563, 1,221, 2,647, 5,736 ms and TR of 7 s. The optimal pulse sequence for MPRAGE with readout flip angle = 8 degrees was found to have five readouts at TIs of 160, 398, 988, 2,455, and 6,102 ms and a TR of 9 s. Further optimization including the readout flip angle suggests that the flip angle should be increased, beyond levels that are acceptable in terms of power deposition and point-spread function.
authors.affiliation: Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Wright
authors.forename: O E
authors.initials: OE
authors.lastname: Mougin
authors.forename: J J
authors.initials: JJ
authors.lastname: Totman
authors.forename: A M
authors.initials: AM
authors.lastname: Peters
authors.forename: M J
authors.initials: MJ
authors.lastname: Brookes
authors.forename: R
authors.initials: R
authors.lastname: Coxon
authors.forename: P E
authors.initials: PE
authors.lastname: Morris
authors.forename: M
authors.initials: M
authors.lastname: Clemence
authors.forename: S T
authors.initials: ST
authors.lastname: Francis
authors.forename: R W
authors.initials: RW
authors.lastname: Bowtell
authors.forename: P A
authors.initials: PA
authors.lastname: Gowland
mesh_terms: D000328:Adult; D000465:Algorithms; D001921:Brain / Q000473:pathology; D002138:Calibration; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008297:Male; D015233:Models, Statistical; D011522:Protons; D015203:Reproducibility of Results; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D014867:Water