title: Extending semiautomatic ventilation defect analysis for hyperpolarized (129)Xe ventilation MRI.
abstract: OBJECTIVE
  Clinical deployment of hyperpolarized (129)Xe magnetic resonance imaging requires accurate quantification and visualization of the ventilation defect percentage (VDP). Here, we improve the robustness of our previous semiautomated analysis method to reduce operator dependence, correct for B1 inhomogeneity and vascular structures, and extend the analysis to display multiple intensity clusters.
  
  
  METHODS
  Two segmentation methods were compared-a seeded region-growing method, previously validated by expert reader scoring, and a new linear-binning method that corrects the effects of bias field and vascular structures. The new method removes nearly all operator interventions by rescaling the (129)Xe magnetic resonance images to the 99th percentile of the cumulative distribution and applying fixed thresholds to classify (129)Xe voxels into four clusters: defect, low, medium, and high intensity. The methods were applied to 24 subjects including patients with chronic obstructive pulmonary disease (n = 8), age-matched controls (n = 8), and healthy normal subjects (n = 8).
  
  
  RESULTS
  Linear-binning enabled a faster and more reproducible workflow and permitted analysis of an additional 0.25 ± 0.18 L of lung volume by accounting for vasculature. Like region-growing, linear-binning VDP correlated strongly with reader scoring (R(2) = 0.93, P < .0001), but with less systematic bias. Moreover, linear-binning maps clearly depict regions of low and high intensity that may prove useful for phenotyping subjects with chronic obstructive pulmonary disease.
  
  
  CONCLUSIONS
  Corrected linear-binning provides a robust means to quantify (129)Xe ventilation images yielding VDP values that are indistinguishable from expert reader scores, while exploiting the entire dynamic range to depict multiple image clusters.
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina.
authors.forename: Mu
authors.initials: M
authors.lastname: He
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina; Department of Biomedical Engineering, Duke University, Durham, North Carolina.
authors.forename: S Sivaram
authors.initials: SS
authors.lastname: Kaushik
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina; Medical Physics Graduate Program, Duke University, Durham, North Carolina.
authors.forename: Scott H
authors.initials: SH
authors.lastname: Robertson
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina; Medical Physics Graduate Program, Duke University, Durham, North Carolina.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Freeman
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina; Department of Biomedical Engineering, Duke University, Durham, North Carolina.
authors.forename: Rohan S
authors.initials: RS
authors.lastname: Virgincar
authors.affiliation: Department of Cardiothoracic Imaging, Duke University Medical Center, Durham, North Carolina.
authors.forename: H Page
authors.initials: HP
authors.lastname: McAdams
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina; Department of Biomedical Engineering, Duke University, Durham, North Carolina; Medical Physics Graduate Program, Duke University, Durham, North Carolina; Department of Radiology, Duke University Medical Center, Durham, North Carolina. Electronic address: bastiaan.driehuys@duke.edu.
authors.forename: Bastiaan
authors.initials: B
authors.lastname: Driehuys
mesh_terms: D000328:Adult; D000368:Aged; D001331:Automation; D016022:Case-Control Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D014979:Xenon Isotopes
chemical_list: D014979:Xenon Isotopes
keywords: Hyperpolarized (129)Xe MRI; image registration; lung segmentation; ventilation defect analysis