3D bronchial simulator: Automatic generation of volumetric CT images for assessment of bronchial parameter quantification methods

The problem of quantifying bronchial parameters from multi-detector computed tomography (MDCT) data has been highly studied in medical research. While the developed methods have been tested and validated on cylindrical computer/physical phantoms or by experimented radiologists on in-vivo/in-vitro CT image data, today-there is no established ground truth enabling to compare the different results. This paper proposes an original approach allowing to simulate CT image acquisitions of realistic 3D bronchus-vessel configurations starting from mesh models of perfectly known parameters, with easily modifiable geometry and topology according to different pathology characteristics. The bronchial simulator platform, 3DAirSim, is composed of several modules: 1) 3D model generation of bronchus inner and outer wall surfaces of different calibers, shapes and orientations, 2) texture volume creation corresponding to the lung parenchyma including or not blood vessels, 3) simulation of CT image acquisition mimicking the scanning process. The proposed model generation method relies on the construction of a consistent 2-manifold surface of a branching tubular structure with given medial axis and local radii. First, a coarse triangular mesh is created by connecting polygonal cross-sections along the medial axis. The model is then refined and locally deformed in the surface normal direction under specific force constraints which stabilize its evolution at the level of the input radii. By generating a pathology-specific database, 3DAirSim will contribute to the creation of a test-bed for bronchial parameter quantification. 3DAirSim is currently used to lead various validations of existing approaches with respect to the clinical objective of airway wall remodeling assessment.