title: Posture-dependent human 3He lung imaging in an open-access MRI system: initial results.
abstract: OBJECTIVE
  The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized (3)He magnetic resonance imaging (MRI) of the human lung, and most other common radiologic imaging modalities including positron emission tomography and computed tomography, restrict subjects to lying horizontally, minimizing most gravitational effects.
  
  
  METHODS
  In this article, we review the motivation for posture-dependent studies of human lung function and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized (3)He gas and an open-access MRI instrument. The open geometry of this MRI system features a "walk-in" capability that permits subjects to be imaged in vertical and horizontal positions and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane.
  
  
  RESULTS
  Initial results include two-dimensional lung images acquired with approximately 4 x 8 mm in-plane resolution and three-dimensional images with approximately 2-cm slice thickness.
  
  
  CONCLUSIONS
  Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden St, MS 59, Cambridge, MA 02138, USA.
authors.forename: Leo L
authors.initials: LL
authors.lastname: Tsai
authors.forename: Ross W
authors.initials: RW
authors.lastname: Mair
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Li
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Rosen
authors.forename: Samuel
authors.initials: S
authors.lastname: Patz
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Walsworth
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D004867:Equipment Design; D006371:Helium; D006801:Humans; D007554:Isotopes; D008168:Lung / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008875:Middle Aged; D011187:Posture / Q000502:physiology*
chemical_list: D007554:Isotopes; D006371:Helium