A streamlined volumetric landmark placement method for building three-dimensional active shape models

For the purpose of building a statistical shape model of a 3D object, a landmarked training set must be obtained. The purpose of this work is to develop a streamlined, slice-by-slice, volumetric landmarking scheme that requires no prior segmentation of the object and directly produces a set of corresponding landmark points for each 3D object in the training set. To achieve inter-object correspondence, the procedure's main feature is the establishment of an object-based coordinate system. Minimal user interaction is employed to locate an origin and axes on each volume by presenting the user with appropriate image slices and annotation tools, as dictated by the data under study. The volumes can then be aligned so that locating a physical point, relative to the established coordinate system, is repeatable from one instance of the object to another. For the purpose of verifying and demonstrating the proposed procedure, a set of test data consisting of image volumes of ten mangoes was obtained. Results of the landmarking scheme for this data, as well as for medical image data, demonstrate good object segmentation and landmark point correspondence.