title: Oxygen-weighted Hyperpolarized (3)He MR Imaging: A Short-term Reproducibility Study in Human Subjects.
abstract: OBJECTIVE
  To determine whether hyperpolarized helium 3 magnetic resonance (MR) imaging to measure alveolar partial pressure of oxygen (Pao2) shows sufficient test-retest repeatability and between-cohort differences to be used as a reliable technique for detection of alterations in gas exchange in asymptomatic smokers.
  
  
  METHODS
  The protocol was approved by the local institutional review board and was HIPAA compliant. Informed consent was obtained from all subjects. Two sets of MR images were obtained 10 minutes apart in 25 subjects: 10 nonsmokers (five men, five women; mean ± standard deviation age, 50 years ± 6) and 15 smokers (seven women, eight men; mean age, 50 years ± 8). A mixed-effects model was developed to identify the regional repeatability of Pao2 measurements as an intraclass correlation coefficient. Ten smokers were matched with the 10 nonsmokers on the basis of signal-to-noise ratio (SNR). Three separate models were generated: one for nonsmokers, one for the SNR-matched smokers, and one for the five remaining smokers, who were imaged with a significantly higher SNR.
  
  
  RESULTS
  Short-term back-to-back regional reproducibility was assessed by using intraclass correlation coefficients, which were 0.67 and 0.65 for SNR case-matched nonsmokers and smokers, respectively. Repeatability was a strong function of SNR; a 50% increase in SNR in the remaining smokers improved the intraclass correlation coefficient to 0.82. Although repeatability was not significantly different between the SNR-matched cohorts (P = .44), the smoker group showed higher spatial and temporal variability in Pao2.
  
  
  CONCLUSIONS
  The short-term test-retest repeatability of hyperpolarized gas MR imaging of regional Pao2 was good. Asymptomatic smokers exhibited greater spatial and temporal variability in Pao2 than did the nonsmokers, which suggests that this parameter allows detection of small functional alterations associated with smoking.
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Masaru
authors.initials: M
authors.lastname: Ishii
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Hooman
authors.initials: H
authors.lastname: Hamedani
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Justin T
authors.initials: JT
authors.lastname: Clapp
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kadlecek
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xin
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Warren B
authors.initials: WB
authors.lastname: Gefter
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Milton D
authors.initials: MD
authors.lastname: Rossman
authors.affiliation: From the Department of Otolaryngology-Head and Neck Surgery, The Johns Hopkins University, Baltimore, Md (M.I., R.R.R.); Department of Radiology (H.H., J.T.C., S.J.K., Y.X., W.G.), and Pulmonary, Allergy and Critical Care Division (M.D.R.), University of Pennsylvania, 308 Stemmler Hall, 3450 Hamilton Walk, Philadelphia, PA 19104.
authors.forename: Rahim R
authors.initials: RR
authors.lastname: Rizi
mesh_terms: D000328:Adult; D005260:Female; D006371:Helium; D006801:Humans; D007554:Isotopes; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010100:Oxygen; D010313:Partial Pressure; D011650:Pulmonary Alveoli; D011659:Pulmonary Gas Exchange; D015203:Reproducibility of Results; D012907:Smoking / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D007554:Isotopes; D006371:Helium; D010100:Oxygen