title: A battery-driven, low-field NMR unit for thermally and hyperpolarized samples.
abstract: OBJECTIVE
  The design of a multinuclear low-field NMR unit with variable field strength <6 mT providing accurate spin manipulations and sufficient sensitivity for direct detection of samples in thermal equilibrium to aid parahydrogen-based hyperpolarization experiments.
  
  
  METHODS
  An optimized, resistive magnet connected to a battery or wall-power driven current source was constructed to provide a magnetic field <6 mT. A digital device connected to a saddle-shaped transmit- and solenoid receive-coil enabled MR signal excitation and detection with up to 10(6) samples/s, controlled by a flexible pulse-programming software.
  
  
  RESULTS
  The magnetization of thermally polarized samples at 1.8 and 5.7 mT is detected in a single acquisition with a SNR ≈10(1) and ≈10(2) and a line width of 42 and 32 Hz, respectively. Nuclear spins are manipulated to an uncertainty of ±1° by means of pulses, which can be arranged in an arbitrary combination. As a demonstration, standard experiments for the measurement of relaxation parameters of thermally polarized samples were implemented. The detection of much stronger hyperpolarized signal was exemplified employing parahydrogen.
  
  
  CONCLUSIONS
  Direct detection of thermal and hyperpolarized (1)H-MR signal in a single acquisition and accurate spin manipulations at 1.8 and 5.5 mT were successfully demonstrated.
authors: Medical Physics, Department of Radiology, University Medical Center Freiburg, Breisacher Straße 60A, 79106, Freiburg, Germany.
authors: Robert
authors: R
authors: Borowiak
authors: Niels
authors: N
authors: Schwaderlapp
authors: Frank
authors: F
authors: Huethe
authors: Thomas
authors: T
authors: Lickert
authors: Elmar
authors: E
authors: Fischer
authors: Sébastien
authors: S
authors: Bär
authors: Jürgen
authors: J
authors: Hennig
authors: Dominik
authors: D
authors: von Elverfeldt
authors: Jan-Bernd
authors: JB
authors: Hövener
mesh_terms: D011211:Electric Power Supplies; D004867:Equipment Design; D006358:Hot Temperature; D006859:Hydrogen / Q000737:chemistry; D060526:Magnetic Fields; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012984:Software; D013997:Time Factors
chemical_list: D006859:Hydrogen