title: Low-temperature dynamic nuclear polarization of gases in Frozen mixtures.
abstract: To present a new cryogenic technique for preparing gaseous compounds in solid mixtures for polarization using dynamic nuclear polarization (DNP).
  
  
  
  (129) Xe and (15) N2 O samples were prepared using the presented method. Samples were hyperpolarized at 1.42K at 5 Tesla. (129) Xe was polarized at 1.65K and 1.42K to compare enhancement. Polarization levels for both samples and T1 relaxation times for the (129) Xe sample were measured. Sample pulverization for the (129) Xe and controlled annealing for both samples were introduced as additional steps in sample preparation.
  
  
  
  Enhancement increased by 15% due to a temperature drop from 1.65K to 1.42K for the (129) Xe sample. A polarization level of 20 ± 3% for the (129) Xe sample was achieved, a two-fold increase from 10 ± 1% after pulverization of the sample at 1.42K. T1 of the (129) Xe sample was increased by more than three-fold by means of annealing. In the case of (15) N2 O, annealing led to a ∼two-fold increase in the signal level after DNP.
  
  
  
  The presented technique for producing and manipulating solid gas/glassing agent/radical mixtures for DNP led to high polarization levels in (129) Xe and (15) N2 O samples. These methods show potential for polarizing other gases using DNP technology. Magn Reson Med 76:1007-1014, 2016. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Electrical and Systems Engineering, University of Pennsylvania, Pennsylvania, USA.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Pourfathi
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Clapp
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kadlecek
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Caroline D
authors.initials: CD
authors.lastname: Keenan
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rajat K
authors.initials: RK
authors.lastname: Ghosh
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Nicholas N
authors.initials: NN
authors.lastname: Kuzma
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D003080:Cold Temperature; D045424:Complex Mixtures / Q000032:analysis / Q000138:chemical synthesis*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005615:Freezing; D005740:Gases / Q000032:analysis / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D011868:Radioisotopes / Q000032:analysis / Q000737:chemistry*; D013048:Specimen Handling / Q000295:instrumentation*; D055672:Static Electricity
chemical_list: D045424:Complex Mixtures; D005740:Gases; D011868:Radioisotopes
keywords: dynamic nuclear polarization; gas MRI; hyperpolarization; sample preparation