Boundary and object labelling in three-dimensional images

There are many imaging modalities (e.g., medical imaging scanners) that capture information about internal structures and generate three-dimensional (3D) digital images of the distribution of some physical property of the material of the structure. Such images have been found to be very useful in analyzing the form and function of the structure and in detecting and correcting deformities in the structure. Visualization of 3D structures is an essential component of such analyses. One commonly used approach to visualization consists of identifying the structure of interest, forming its surfaces, and then rendering the surfaces on a two-dimensional screen. This paper addresses the surface formation problem assuming that object identification has already been done and a 3D binary image is available that represents the structure. For the existing 3D boundary tracking algorithms, the user has to somehow specify each surface that is to be tracked. Often, the 3D image consists of many surfaces of interest. Their manual specification is very tedious and may be impossible if the structure is of complex shape. This paper describes a methodology for automatically tracking all boundary surfaces—i.e., labelling boundary surfaces—in the given 3D image. The algorithms also generate additional information from which the 3D connected components in the image are trivially obtained. Examples from medical imaging are included to illustrate the usefulness of the new methodology.