title: Pulmonary functional magnetic resonance imaging: asthma temporal-spatial maps.
abstract: OBJECTIVE
  Hyperpolarized (3)He magnetic resonance imaging (MRI) previously revealed the temporal and spatial heterogeneity of ventilation defects in asthmatics, but these findings have not been used in treatment studies or to guide personalized therapy. Our objective was to exploit the temporal and spatial information inherent to (3)He MRI and develop image processing methods to generate pulmonary ventilation temporal-spatial maps that could be used to measure, optimize, and guide asthma therapy.
  
  
  METHODS
  In this proof-of-concept study, seven asthmatics provided written informed consent to an approved protocol and underwent spirometry and (3)He MRI on three occasions, each 5 ± 2 days apart. A registration and segmentation pipeline was developed to generate three-dimensional, temporal-spatial, pulmonary function maps. Briefly, (3)He ventilation images were segmented to generate ventilation masks that were coregistered and voxels classified according to their temporal behavior. This enabled the regional mapping of temporally persistent and intermittent ventilation defects that were normalized to the (1)H MRI thoracic cavity volume to generate persistent ventilation defect percent (VDPP) and intermittent ventilation defect percent (VDPI).
  
  
  RESULTS
  (3)He temporal-spatial pulmonary function maps identified temporally persistent and intermittent ventilation defects. VDP(I) was significantly greater in the posterior (P = .04) and inferior (P = .04) lung as compared to the anterior and superior lung. Persistent and intermittent ventilation defect percent were strongly correlated with forced expiratory volume in one second/forced vital capacity (VDP(P): r = -0.87, P = .01; VDP(I): r = -0.96, P = .0008).
  
  
  CONCLUSIONS
  Temporal-spatial pulmonary maps generated from (3)He MRI can be used to quantify temporally persistent and intermittent ventilation defects as asthma intermediate end points and targets for therapy.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, Western University, 1151 Richmond St North, London, Ontario, Canada N6A 5B7; Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Svenningsen
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, Western University, 1151 Richmond St North, London, Ontario, Canada N6A 5B7; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario, Canada.
authors.forename: Fumin
authors.initials: F
authors.lastname: Guo
authors.affiliation: Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; UBC James Hogg Research Centre and The Institute of Heart and Lung Health, St. Paul's Hospital, Vancouver, British Columbia, Canada.
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirby
authors.affiliation: Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Stephen
authors.initials: S
authors.lastname: Choy
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, Western University, 1151 Richmond St North, London, Ontario, Canada N6A 5B7.
authors.forename: Andrew
authors.initials: A
authors.lastname: Wheatley
authors.affiliation: Division of Respirology, Department of Medicine, The University of Western Ontario, London, Ontario, Canada.
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, Western University, 1151 Richmond St North, London, Ontario, Canada N6A 5B7; Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada; Graduate Program in Biomedical Engineering, The University of Western Ontario, London, Ontario, Canada; Department of Medical Imaging, The University of Western Ontario, London, Ontario, Canada. Electronic address: gparraga@robarts.ca.
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology*; D003287:Contrast Media; D005260:Female; D006371:Helium; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes; D008168:Lung / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D062211:Spatio-Temporal Analysis; D055815:Young Adult
chemical_list: D003287:Contrast Media; D007554:Isotopes; D019275:Radiopharmaceuticals; D006371:Helium
keywords: hyperpolarized (3)He magnetic resonance imaging; image-guided therapy; lung function; sthma; ventilation defect