title: Accurate measurement of intrathoracic airways.
abstract: Airway geometry measurements can provide information regarding pulmonary physiology and pathophysiology. There has been considerable interest in measuring intrathoracic airways in two-dimensional (2-D) slices from volumetric X-ray computed tomography (CT). Such measurements can be used to evaluate and track the progression of diseases affecting the airways. A popular airway measurement method uses the "half-max" criteria, in which the gray level at the airway wall is estimated to be halfway between the minimum and maximum gray levels along a ray crossing the edge. However, because the scanning process introduces blurring, the half-max approach may not be applicable across all airway sizes. We propose a new measurement method based on a model of the scanning process. In our approach, we examine the gray-level profile of a ray crossing the airway wall and use a maximum-likelihood method to estimate the airway inner and outer radius. Using CT scans of a physical phantom, we present results showing that the new approach is more accurate than the half-max method at estimating wall location for thin-walled airways.
authors.affiliation: Department of Biomedical Engineering, University of Iowa, Iowa City 52242, USA. joe-reinhardt@uiowa.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Reinhardt
authors.forename: N D
authors.initials: ND
authors.lastname: D'Souza
authors.forename: E A
authors.initials: EA
authors.lastname: Hoffman
mesh_terms: D001980:Bronchi / Q000033:anatomy & histology; D001995:Bronchography; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods