title: CT-measured regional specific volume change reflects regional ventilation in supine sheep.
abstract: Computer tomography (CT) imaging techniques permit the noninvasive measurement of regional lung function. Regional specific volume change (sVol), determined from the change in lung density over a tidal breath, should correlate with regional ventilation and regional lung expansion measured with other techniques. sVol was validated against xenon (Xe)-CT-specific ventilation (sV) in four anesthetized, intubated, mechanically ventilated sheep. Xe-CT used expiratory gated axial scanning during the washin and washout of 55% Xe. sVol was measured from the tidal changes in tissue density (H, houndsfield units) of lung regions using the relationship sVol = [1,000(Hi - He)]/[He(1,000 + Hi)], where He and Hi are expiratory and inspiratory regional density. Distinct anatomical markings were used to define corresponding lung regions of interest between inspiratory, expiratory, and Xe-CT images, with an average region of interest size of 1.6 +/- 0.7 ml. In addition, sVol was compared with regional volume changes measured directly from the positions of implanted metal markers in an additional animal. A linear relationship between sVol and sV was demonstrated over a wide range of regional sV found in the normal supine lung, with an overall correlation coefficient (R(2)) of 0.66. There was a tight correlation (R(2) = 0.97) between marker-measured volume changes and sVol. Regional sVol, which involves significantly reduced exposure to radiation and Xe gas compared with the Xe-CT method, represents a safe and efficient surrogate for measuring regional ventilation in experimental studies and patients.
authors.affiliation: Department of Anesthesiology, Johns Hopkins Hospital, Baltimore, MD 21287, USA.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Fuld
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.forename: Osama I
authors.initials: OI
authors.lastname: Saba
authors.forename: Deokiee
authors.initials: D
authors.lastname: Chon
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Reinhardt
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hoffman
authors.forename: Brett A
authors.initials: BA
authors.lastname: Simon
mesh_terms: D000465:Algorithms; D000818:Animals; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D008176:Lung Volume Measurements / Q000379:methods*; D015233:Models, Statistical; D015656:Respiratory Mechanics / Q000502:physiology*; D012756:Sheep; D016683:Supine Position / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D014978:Xenon
chemical_list: D014978:Xenon