title: High spatial resolution hyperpolarized3He MRI of the rodent lung using a single breath X-centric gradient-recalled echo approach.
abstract: OBJECTIVE
  Hyperpolarized (HP) gas MRI of the rodent lung is of great interest because of the increasing need for novel biomarkers with which to develop new therapies for respiratory diseases. The use of fast gradient-recalled echo (FGRE) for high-resolution HP gas rodent lung MRI is challenging as a result of signal loss caused by significant diffusion weighting, particularly in the larger airways. In this work, a modified FGRE approach is described for HP3He rodent lung MRI using a centric-out readout scheme (ie, x-centric), allowing high-resolution, density-weighted imaging.
  
  
  METHODS
  HP3He x-centric imaging was performed in a phantom and compared with a conventional partial-echo FGRE acquisition for in-plane spatial resolutions varying between 39 and 312 µm. Partial-echo and x-centric acquisitions were also compared for high spatial-resolution breath-hold (1 s) imaging of rodent lungs.
  
  
  RESULTS
  X-centric provided improved signal-to-noise ratio efficiency by a factor of up to 13/1.7 and 6.7/1.8, compared with the partial-echo FGRE for the airways/parenchyma of mouse and rat, respectively, at high spatial resolutions in vivo (<78 µm). In particular, rodent major airways with less restricted diffusion of3He could only be visualized with the x-centric method.
  
  
  CONCLUSIONS
  The x-centric method significantly reduces diffusion weighting, allowing high spatial and temporal resolution HP3He gas density-weighted rodent lung MRI. Magn Reson Med 78:2334-2341, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Canada.|Department of Medical Biophysics, The University of Western Ontario, London, Canada.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Ouriadov
authors.affiliation: Department of Medical Biophysics, University of Toronto, Toronto, Canada.|Physiology & Experimental Medicine Program, Peter Gilgan Centre for Research and Learning, the Hospital for Sick Children, Toronto, Canada.
authors.forename: Giles E
authors.initials: GE
authors.lastname: Santyr
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D004058:Diffusion; D017352:Echo-Planar Imaging; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D012123:Pulmonary Ventilation; D051381:Rats; D017208:Rats, Wistar; D012120:Respiration Disorders / Q000000981:diagnostic imaging; D059629:Signal-To-Noise Ratio
chemical_list: D015415:Biomarkers
keywords: hyperpolarized 3He; rodent lung; x-centric FGRE