Combination of shape-constrained and inflation deformable models with application to the segmentation of the left atrial appendage

This paper introduces a method for the flexible model-based segmentation of the whole heart from 3D CT images. The novelty of the approach is the combination in a single framework of two types of deformable models. The anatomical structures with well defined shapes (like the cardiac chambers) are segmented with deformable models constraining the deforming surface to stay close to some shape prior. On the other hand, structures with highly variable shapes are extracted by locally inflating the deforming surface without strong assumptions on the shape of the object to segment. The proposed method has been applied to the segmentation of the heart of 17 patients. Cardiac chambers and major vessels were segmented using shape-constrained deformable models while the left atrial appendage (LAA) was extracted using the mesh inflation. Qualitatively, the mesh resulting from the inflation adapts well to the difficult shape of the LAA. However, reaching the very tip of this elongated structure remains difficult. These results are numerically confirmed with manually generated reference segmentations.