title: In vivo lung morphometry with hyperpolarized (3) He diffusion MRI: reproducibility and the role of diffusion-sensitizing gradient direction.
abstract: OBJECTIVE
  Lung morphometry with hyperpolarized gas diffusion MRI is a highly sensitive technique for the noninvasive measurement of acinar microstructural parameters traditionally only accessible by histology. The goal of this work is to establish the reproducibility of these measurements in healthy volunteers and their dependence on the direction of the applied diffusion-sensitizing gradient.
  
  
  METHODS
  Hyperpolarized helium-3 ((3) He) lung morphometry MRI was performed on a total of five healthy subjects. Two subjects received duplicate imaging on the same day and three subjects received duplicate imaging after a 4-month or 27-month delay to assess reproducibility. Four subjects repeated the measurement during the same session with different diffusion-sensitizing gradient directions to determine the effect on the parameter estimates.
  
  
  RESULTS
  The (3) He lung morphometry measurements were reproducible over the short term and long term (e.g., % coefficient of variation [CV] of mean chord length, Lm = 2.1% and 2.9%, respectively) and across different diffusion gradient directions (Lm % CV = 2.6%). Results also show independence of field inhomogeneity effects at 1.5T.
  
  
  CONCLUSIONS
  (3) He lung morphometry is a reproducible technique for measuring acinar microstructure and is effectively independent of the choice of diffusion gradient direction. This provides confidence for the use of this technique to compare populations and treatment efficacy.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Quirk
authors.forename: Yulin V
authors.initials: YV
authors.lastname: Chang
authors.forename: Dmitriy A
authors.initials: DA
authors.lastname: Yablonskiy
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000465:Algorithms; D003287:Contrast Media / Q000008:administration & dosage; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006371:Helium / Q000008:administration & dosage / Q000737:chemistry; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes / Q000008:administration & dosage / Q000737:chemistry; D008168:Lung / Q000033:anatomy & histology* / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D003287:Contrast Media; D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium
keywords: MRI; diffusion; helium; hyperpolarized gas; lung morphometry; reproducibility
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