title: Quantification of human lung structure and physiology using hyperpolarized 129Xe.
abstract: OBJECTIVE
  To present in vivo, human validation of a previously proposed method to measure key pulmonary parameters related to lung microstructure and physiology. Some parameters, such as blood-air barrier thickness, cannot be measured readily by any other noninvasive modality.
  
  
  METHODS
  Healthy volunteers (n = 12) were studied in 1.5T and 3T whole body human scanners using hyperpolarized xenon. Xenon uptake by lung parenchyma and blood was measured using a chemical shift saturation recovery sequence. Both dissolved-xenon peaks at 197 ppm and 217-218 ppm were fitted against a model of xenon exchange (MOXE) as functions of exchange time. Parameters related to lung function and structure can be obtained by fitting to this model.
  
  
  RESULTS
  The following results were obtained from xenon uptake (averaged over all healthy volunteers): surface-area-to-volume ratio = 210 ± 50 cm(-1) ; total septal wall thickness = 9.2 ± 6.5 μm; blood-air barrier thickness = 1.0 ± 0.3 μm; hematocrit = 27 ± 4%; pulmonary capillary blood transit time = 1.3 ± 0.3 s, in good agreement with literature values from invasive experiments. More detailed fitting results are listed in the text.
  
  
  CONCLUSIONS
  The initial in vivo human results demonstrate that our proposed methods can be used to noninvasively determine lung physiology by simultaneous quantification of a few important pulmonary parameters. This method is highly promising to become a versatile screening method for lung diseases.
authors.affiliation: Biomedical Magnetic Resonance Laboratory, Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, USA; Department of Physics, Washington University, St. Louis, Missouri, USA.
authors.forename: Yulin V
authors.initials: YV
authors.lastname: Chang
authors.forename: James D
authors.initials: JD
authors.lastname: Quirk
authors.forename: Iulian C
authors.initials: IC
authors.lastname: Ruset
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Atkinson
authors.forename: F William
authors.initials: FW
authors.lastname: Hersman
authors.forename: Jason C
authors.initials: JC
authors.lastname: Woods
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008168:Lung / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D012016:Reference Values; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods; D012680:Sensitivity and Specificity; D013990:Tidal Volume / Q000502:physiology*; D014979:Xenon Isotopes / Q000008:administration & dosage; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D014979:Xenon Isotopes
keywords: Fahraeus effect; barrier thickness; field-dependent chemical shift; lung physiology; surface-area-to-volume ratio