title: CT-based assessment of regional pulmonary microvascular blood flow parameters.
abstract: To determine regional pulmonary microvascular mean transit times (MTTs), we used electrocardiogram-gated X-ray computed tomographic imaging to follow bolus radiopaque contrast material through the lungs in anesthetized animals (7 dogs and 1 pig, prone and supine). By deconvolution/reconvolution of regional time-attenuation curves obtained from parenchyma and large lobar arteries, we estimated the microvascular residue function and reconstituted the regional microvascular time-attenuation curves and, thus, regional microvascular MTTs. The mean microvascular MTTs in the supine and prone postures were 3.94 +/- 1.0 and 3.40 +/- 0.84 (mean +/- SD), respectively. The dependent-nondependent vertical gradient of MTT was greater in the supine [slope = 0.25 +/- 0.10 (SD), P < 0.001 by t-test] than in the prone (-0.03 +/- 0.06 in 6 of 8 animals; 2 outliers had positive slopes) posture. In both postures, there was a trend toward faster transit times in the dorsal-basal lung region in six of the eight animals, suggesting gravity-independent higher vascular conductance dorsocaudally. We conclude that deconvolution methods, in association with electrocardiogram-gated high-speed X-ray computed tomography, can provide insights into regional heterogeneity of pulmonary microvascular MTT in vivo.
authors.affiliation: Department of Radiology, University of Iowa, Iowa City, Iowa 52241, USA.
authors.forename: Chulho
authors.initials: C
authors.lastname: Won
authors.forename: Deokiee
authors.initials: D
authors.lastname: Chon
authors.forename: Jehangir
authors.initials: J
authors.lastname: Tajik
authors.forename: Binh Q
authors.initials: BQ
authors.lastname: Tran
authors.forename: G Blake
authors.initials: GB
authors.lastname: Robinswood
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Beck
authors.forename: Eric A
authors.initials: EA
authors.lastname: Hoffman
mesh_terms: D000818:Animals; D004285:Dogs; D004562:Electrocardiography; D008833:Microcirculation; D009010:Monte Carlo Method; D016684:Prone Position / Q000502:physiology; D011652:Pulmonary Circulation; D016683:Supine Position / Q000502:physiology; D013552:Swine; D014057:Tomography, X-Ray Computed