title: Xenon-enhanced dual-energy CT of patients with asthma: dynamic ventilation changes after methacholine and salbutamol inhalation.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the use of xenon-enhanced dual-energy CT of the chest to assess ventilation changes after methacholine and salbutamol inhalation in subjects with asthma and healthy subjects.
  
  
  METHODS
  Twenty-five subjects with asthma and 10 healthy subjects underwent three-phase (basal, after methacholine inhalation, after salbutamol inhalation) xenon-enhanced chest CT. Each phase was composed of wash-in and washout scans. For visual analysis, two radiologists evaluated ventilation defects and gas trapping lobe by lobe on a 10-point scale. Total ventilation defect and gas trapping scores were calculated by adding ventilation defect and gas trapping scores. Xenon and total lung volume were quantified automatically. Total xenon concentration index was calculated as total xenon concentration divided by lung volume. Repeated measures analysis of variance and Student t test were used for comparisons of total ventilation defect score, total gas trapping score, and total xenon concentration index between the two groups. The Friedman test was used for within-group analysis.
  
  
  RESULTS
  In the basal state, subjects with asthma had a higher total ventilation defect score (p = 0.004) and higher total gas trapping score (p = 0.05) than did healthy subjects. On washout images, total ventilation defect score, total gas trapping score, and total xenon concentration index after methacholine and salbutamol inhalation were statistically different between the two groups (p < 0.05). However, total xenon concentration index on wash-in images was not significantly different between the two groups. In within-group analysis, total ventilation defect score and total gas trapping score in subjects with asthma and total ventilation defect score in healthy subjects increased significantly after methacholine inhalation and decreased significantly after salbutamol inhalation (p < 0.05).
  
  
  CONCLUSIONS
  Xenon-enhanced chest CT may be a useful technique for visualizing dynamic changes in airflow in response to methacholine and salbutamol inhalation in patients with asthma. Optimization of the protocol for radiation exposure is warranted.
authors.affiliation: Department of Radiology, Seoul National University Hospital and Institute of Radiation Medicine, Seoul National University Medical Research Center, 101 Daehangno Jongno-gu, Seoul 110-744, Korea.
authors.forename: Won Wha
authors.initials: WW
authors.lastname: Kim
authors.forename: Chang Hyun
authors.initials: CH
authors.lastname: Lee
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Goo
authors.forename: Sang Joon
authors.initials: SJ
authors.lastname: Park
authors.forename: Jong Hyo
authors.initials: JH
authors.lastname: Kim
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: Park
authors.forename: Sang-Heon
authors.initials: SH
authors.lastname: Cho
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage*; D000704:Analysis of Variance; D001249:Asthma / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage*; D001993:Bronchodilator Agents / Q000008:administration & dosage*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage*; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014978:Xenon / Q000493:pharmacokinetics
chemical_list: D016085:Bronchoconstrictor Agents; D001993:Bronchodilator Agents; D016210:Methacholine Chloride; D014978:Xenon; D000420:Albuterol