title: Regional anisotropy of airspace orientation in the lung as assessed with hyperpolarized helium-3 diffusion MRI.
abstract: OBJECTIVE
  To evaluate regional anisotropy of lung-airspace orientation by assessing the dependence of helium-3 ((3) He) apparent diffusion coefficient (ADC) values on the direction of diffusion sensitization at two field strengths.
  
  
  METHODS
  Hyperpolarized (3) He diffusion-weighted magnetic resonance imaging (MRI) of the lung was performed at 0.43T and 1.5T in 12 healthy volunteers. A gradient-echo pulse sequence was used with a bipolar diffusion-sensitization gradient applied separately along three orthogonal directions. ADC maps, median ADC values, and signal-to-noise ratios were calculated from the diffusion-weighted images. Two readers scored the ADC maps for increased values at lung margins, major fissures, or within focal central regions.
  
  
  RESULTS
  ADC values were found to depend on the direction of diffusion sensitization (P < 0.01, except for craniocaudal vs. anteroposterior directions at 1.5T) and were increased at the lateral and medial surfaces for left-right diffusion sensitization (12 of 12 subjects); at the apex and base (9 of 12), and along the major fissure (8 of 12), for craniocaudal diffusion sensitization; and at the most anterior and posterior lung (10 of 12) for anteroposterior diffusion sensitization. Median ADC values at 0.43T (0.201 ± 0.017, left-right; 0.193 ± 0.019, craniocaudal; and 0.187 ± 0.017 cm(2) /s, anteroposterior) were slightly lower than those at 1.5T (0.205 ± 0.017, 0.197 ± 0.017 and 0.194 ± 0.016 cm(2) /s, respectively; P < 0.05).
  
  
  CONCLUSIONS
  These findings indicate that diffusion-weighted hyperpolarized (3) He MRI can detect regional anisotropy of lung-airspace orientation, including that associated with preferential orientation of terminal airways near pleural surfaces.
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Komlosi
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: Talissa A
authors.initials: TA
authors.lastname: Altes
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.|Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Kun
authors.initials: K
authors.lastname: Qing
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Mooney
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: G Wilson
authors.initials: GW
authors.lastname: Miller
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: Jaime F
authors.initials: JF
authors.lastname: Mata
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: Eduard E
authors.initials: EE
authors.lastname: de Lange
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Tobias
authors.affiliation: Department of Physics, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Cates
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.|Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Brookeman
authors.affiliation: Center for In-vivo Hyperpolarized Gas MR Imaging, Department of Radiology & Medical Imaging, University of Virginia School of Medicine, Charlottesville, Virginia, USA.|Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Mugler
mesh_terms: D000328:Adult; D016880:Anisotropy; D003198:Computer Simulation; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006371:Helium; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes; D008168:Lung / Q000033:anatomy & histology*; D060526:Magnetic Fields; D008297:Male; D008954:Models, Biological; D019275:Radiopharmaceuticals; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium
keywords: anisotropy; diffusion-weighted MRI; hyperpolarized gas; lung