title: Ultra-short echo-time pulmonary MRI: evaluation and reproducibility in COPD subjects with and without bronchiectasis.
abstract: BACKGROUND
  To evaluate ultra-short-echo-time (UTE) MRI pulmonary signal-intensity measurements and reproducibility in chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  A two-dimensional sequence (echo-time = 0.05 ms; acquisition-time = 13 s) with interleaved half-pulse excitation and radial ramp-sampling was used with compressed-sensing to reconstruct UTE images from under-sampled data. Five healthy volunteers and 15 subjects with COPD provided written informed consent to imaging and pulmonary-function-tests. Healthy volunteers underwent MRI at four lung volumes: full-expiration, functional-residual-capacity (FRC), FRC+1L, and full-inhalation; COPD patients underwent computed-tomography (CT) and MRI at FRC+1L. Three-week reproducibility was evaluated and the relative area of the density histogram ≤ -950 HU (RA950 ) was compared with mean MRI signal-intensity. The 15th percentile of signal-intensity-histogram (SI15 ) was compared with the 15th percentile of the CT-density-histogram (HU15 ).
  
  
  RESULTS
  In healthy subjects, signal-intensity correlated with the inverse of lung volume (r = 0.99; P = 0.007). Contrast-to-noise and signal-to-noise ratios were significantly improved for 32-channel UTE (P < 0.01). The coefficient of variation for 3-week repeated measurements was 4%. There were significant correlations for signal-intensity with RA950 (r = -0.71; P = 0.005), FEV1 /FVC (r = 0.59; P = 0.02), and for SI15 with HU15 (r = 0.62; P = 0.01).
  
  
  CONCLUSIONS
  Pulmonary signal-intensity is reproducible and related to tissue density. In COPD subjects with and without bronchiectasis, signal-intensity was also related to pulmonary function and CT measurements.
authors: Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Canada.
authors: Weijing
authors: W
authors: Ma
authors: Khadija
authors: K
authors: Sheikh
authors: Sarah
authors: S
authors: Svenningsen
authors: Damien
authors: D
authors: Pike
authors: Fumin
authors: F
authors: Guo
authors: Roya
authors: R
authors: Etemad-Rezai
authors: Jonathan
authors: J
authors: Leipsic
authors: Harvey O
authors: HO
authors: Coxson
authors: David G
authors: DG
authors: McCormack
authors: Grace
authors: G
authors: Parraga
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001987:Bronchiectasis / Q000150:complications / Q000473:pathology*; D044962:Data Compression / Q000379:methods; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: 1H MRI; COPD; bronchiectasis; ultra-short echo time