title: Versatile pulse sequence device to conserve hyperpolarization for NMR and MRI studies.
abstract: OBJECTIVE
  Levitt and co-workers have described the M2S pulse sequence which transfers between longitudinal and singlet spin order. Building on this work, we describe the construction of a portable M2S pulse sequence generator to increase the relaxation time of polarized compounds. Additionally, we investigate the efficiency of spin order transfer under conditions where physical parameters of the system are not known precisely.
  
  
  METHODS
  A portable M2S generator is built. Longitudinally polarized N2O is converted to the singlet state by both adiabatic transfer and by the M2S sequence. Density matrix simulations are used to model the effects of mismatched chemical shift, flip angle, and scalar couplings.
  
  
  RESULTS
  Density matrix simulations suggest that to convert 95% of the longitudinal m = 1 triplet state population to the singlet order we must match the Larmor precession frequency to the excitation radiofrequency field by 10%, the scalar couplings must be determined to better than 0.6%, and the flip angle must be calibrated to better than 2%.
  
  
  CONCLUSIONS
  The sequence is robust against many mismatched physical parameters of the species we are converting. Additionally, the instrument's portability allows for the conversion of hyperpolarized species near a polarizer. The lifetime is increased by ∼12-fold. This is highly advantageous in systems where the hyperpolarized media relax rapidly.
authors.affiliation: Institutional Information: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rajat K
authors.initials: RK
authors.lastname: Ghosh
authors.affiliation: Institutional Information: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Nicholas N
authors.initials: NN
authors.lastname: Kuzma
authors.affiliation: Institutional Information: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kadlecek
authors.affiliation: Institutional Information: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D003198:Computer Simulation; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D008962:Models, Theoretical; D009609:Nitrous Oxide / Q000737:chemistry
chemical_list: D009609:Nitrous Oxide
keywords: magnetization; nuclear magnetic resonance; spin polarized transport