title: Krypton ventilation imaging using dual-energy CT in chronic obstructive pulmonary disease patients: initial experience.
abstract: OBJECTIVE
  To evaluate the tolerance and level of enhancement achievable after inhalation of stable krypton.
  
  
  METHODS
  This study was approved by the institutional review board and the local ethics committee. Written informed consent was obtained from all subjects. The study was planned as a Fleming two-stage design, enabling one to assess the effectiveness of a newer treatment or technique on a small number of patients. At the end of each stage, the results are computed, and the trial can be stopped if the effectiveness is less than a minimum success rate or greater than an expected success rate. After informed consent was obtained, a total of 32 patients (ie, two successive series of 16 patients each) with severe emphysema underwent a dual-source, dual-energy chest computed tomographic (CT) examination after inhalation of a mixture of stable krypton (80%) and oxygen (20%), with reconstruction of diagnostic and ventilation images. For each patient, two regions of interest were selected on a diagnostic image, one in a region of severe emphysema (presumed to be poorly ventilated or not ventilated) and a second one in a region devoid of structural abnormalities (presumed to be normally ventilated), with measurements of attenuation values on the corresponding ventilation image.
  
  
  RESULTS
  All examinations were successfully performed, without adverse effects. Differences in attenuation between normal lung and emphysematous areas were found in 28 patients (88%; 95% confidence interval: 71%, 96.5%). The maximal level of attenuation within normal lung was 18.5 HU. Krypton attenuation difference between normal and emphysematous lung was significant, with a median value of 51.8% (P < .001).
  
  
  CONCLUSIONS
  The level of enhancement after inhalation of krypton and its excellent clinical tolerance makes this gas eligible for ventilation CT examinations.
authors.affiliation: Department of Thoracic Imaging, Hôpital Calmette (EA 2694), Université Lille Nord de France, Boulevard Jules Leclercq, F-59000 Lille, France.
authors.forename: Anne-Lise
authors.initials: AL
authors.lastname: Hachulla
authors.forename: François
authors.initials: F
authors.lastname: Pontana
authors.forename: Lidwine
authors.initials: L
authors.lastname: Wemeau-Stervinou
authors.forename: Suonita
authors.initials: S
authors.lastname: Khung
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Faivre
authors.forename: Benoit
authors.initials: B
authors.lastname: Wallaert
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Cazaubon
authors.forename: Alain
authors.initials: A
authors.lastname: Duhamel
authors.forename: Thierry
authors.initials: T
authors.lastname: Perez
authors.forename: Patrick
authors.initials: P
authors.lastname: Devos
authors.forename: Jacques
authors.initials: J
authors.lastname: Remy
authors.forename: Martine
authors.initials: M
authors.lastname: Remy-Jardin
mesh_terms: D005260:Female; D006801:Humans; D007726:Krypton; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D007726:Krypton