title: Pulmonary ventilation visualized using hyperpolarized helium-3 and xenon-129 magnetic resonance imaging: differences in COPD and relationship to emphysema.
abstract: In subjects with chronic obstructive pulmonary disease (COPD), hyperpolarized xenon-129 ((129)Xe) magnetic resonance imaging (MRI) reveals significantly greater ventilation defects than hyperpolarized helium-3 ((3)He) MRI. The physiological and/or morphological determinants of ventilation defects and the differences observed between hyperpolarized (3)He and (129)Xe MRI are not yet understood. Here we aimed to determine the structural basis for the differences in ventilation observed between (3)He and (129)Xe MRI in subjects with COPD using apparent diffusion coefficients (ADC) and computed tomography (CT). Ten COPD ex-smokers provided written, informed consent and underwent MRI, CT, spirometry, and plethysmography. (3)He and (129)Xe MRI ventilation volume was generated using semiautomated segmentation, and ADC maps were registered to generate ADC values for lung regions of interest ventilated by both gases (ADCHX) and by (3)He gas only (ADCHO). CT wall area percentage and the lowest 15th percentile point of the CT lung density histogram (HU15%) were also evaluated. For lung regions accessed by (3)He gas only, mean (3)He ADCHO was significantly greater than for regions accessed by both gases (ADCHO = 0.503 ± 0.119 cm(2)/s, ADCHX = 0.470 ± 0.125 cm(2)/s, P < 0.0001). The difference between (3)He and (129)Xe ventilation volume was significantly correlated with CT HU15% (r = -65, P = 0.04) and (3)He ADCHO (r = 0.70, P = 0.02), but not CT wall area percentage (r = -0.34, P = 0.33). In conclusion, in this small study in COPD subjects, we observed significantly decreased (129)Xe MRI ventilation compared with (3)He MRI, and these regions of decreased (129)Xe ventilation were spatially and significantly correlated with regions of increased pulmonary emphysema, but not airway wall thickness.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.forename: Sarah
authors.initials: S
authors.lastname: Svenningsen
authors.forename: Nikhil
authors.initials: N
authors.lastname: Kanhere
authors.forename: Amir
authors.initials: A
authors.lastname: Owrangi
authors.forename: Andrew
authors.initials: A
authors.lastname: Wheatley
authors.forename: Harvey O
authors.initials: HO
authors.lastname: Coxson
authors.forename: Giles E
authors.initials: GE
authors.lastname: Santyr
authors.forename: Nigel A M
authors.initials: NA
authors.lastname: Paterson
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006371:Helium; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D012123:Pulmonary Ventilation; D012720:Severity of Illness Index; D059629:Signal-To-Noise Ratio; D013147:Spirometry; D014057:Tomography, X-Ray Computed; D014979:Xenon Isotopes
chemical_list: D003287:Contrast Media; D014979:Xenon Isotopes; D006371:Helium