title: Hyperpolarized 129Xe MR imaging with balanced steady-state free precession in spontaneously breathing mouse lungs.
abstract: OBJECTIVE
  We investigated the characteristics of hyperpolarized (HP) (129)Xe magnetic resonance (MR) imaging obtained from balanced steady-state free precession (SSFP) measurement of mouse lungs, especially under spontaneous breathing, and compared the results with those obtained using traditional spoiled gradient echo (SPGR) method, focusing on improved signal-to-noise ratio (SNR) and reduced total acquisition time.
  
  
  METHODS
  We calculated magnetization response of the HP (129)Xe gas for the balanced SSFP sequence under spontaneous breathing to derive optimal conditions for the imaging experiment. We then placed an anesthetized mouse in the magnet (9.4T) supplied with oxygen gas and a mixture of HP (129)Xe gas supplied from a continuous-flow hyperpolarizing system. We obtained an axial plane image of the lung through balanced SSFP and SPGR sequences, changing the various magnetic resonance (MR) imaging parameters, and measured the SNR of these images.
  
  
  RESULTS
  We demonstrated the clear dependence of image intensity on flip angle and number of shots. The SNR was higher in balanced SSFP than in SPGR and 2.3-fold higher compared at each maximum. In contrast, total acquisition time in balanced SSFP was shortened to about one-eighth that of SPGR using a one-shot acquisition mode.
  
  
  CONCLUSIONS
  In HP (129)Xe MR imaging of the lung of a spontaneously breathing mouse, balanced SSFP sequence with multi-shot and centric order acquisition provides higher SNR in a shorter acquisition time than SPGR.
authors: Division of Medical Physics and Engineering, Area of Medical Technology and Science, Course of Health Science, Graduate School of Medicine, Osaka University, Suita, Japan. kk_nest_003_fi@yahoo.co.jp
authors: Fumito
authors: F
authors: Imai
authors: Ryosuke
authors: R
authors: Kashiwagi
authors: Hirohiko
authors: H
authors: Imai
authors: Satoshi
authors: S
authors: Iguchi
authors: Atsuomi
authors: A
authors: Kimura
authors: Hideaki
authors: H
authors: Fujiwara
mesh_terms: D000818:Animals; D005740:Gases; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008168:Lung / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D012119:Respiration; D014979:Xenon Isotopes
chemical_list: D005740:Gases; D014979:Xenon Isotopes