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Follow-up studies of bronchial wall remodeling in asthmatics based on multi-detector computed tomography (MDCT)
imaging is the emerging modality for therapy assessment. While providing statistically significant quantification of
global variation before/after treatment, the employed cross-section-area estimation techniques cannot guarantee the
absolute accuracy of point-by-point estimation. Such uncertainty comes from the impossibility to define an accurate
cross-sectional plane of a bronchus at locations where the notion of central axis is questionable. In order to overcome
such limitation, this paper develops an original automated volumetric approach for bronchial wall quantification
involving a successive model-based 3D reconstruction of the inner and outer bronchial wall surfaces. The inner surface
is segmented by means of strong 3D morphological filtering and model-fitting. An optimal geometrico-topological
model is generated by using a restricted Delaunay triangulation approach. The model is then dynamically deformed in
the surface normal direction, under the constraint of local energy minimization acting at each evolving vertex. The
energy potentials oppose a mesh-derived elastic component combining topological and geometric features in order to
preserve shape regularity, and an expansion potential exploiting image characteristics. The deformation process both
adapts the mesh resolution and handles topology changes and auto-collisions. The developed 3D modeling stabilizes the
deformation at the level of the outer surface of the bronchial wall and provides robustness with respect to bronchus-blood
vessel contacts, where image data is irrelevant. The accuracy of the volumetric segmentation approach was
evaluated with respect to 3D mathematically-simulated phantoms of bronchial subdivisions. Comparisons with recent
2D techniques, carried out on simulated and real MDCT data showed similar performances in cross-section wall area
quantification. The benefit of using volumetric versus cross-section area quantification is finally argued in the context
of bronchial reactivity and wall remodeling follow-up.
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