Three dimensional digital atlas of the orbit constructed from multi-modal radiological images

The human orbit has numerous structures packed in a relatively small space, the study of which is essential and difficult due to complex three dimensional relationships. Available printed orbital atlases do not convey the three dimensional information and are not interactive. To overcome these limitations, we built a digital 3D orbital atlas presented in axial, coronal and sagittal planes, and as three dimensional geometric models of the muscles, bones, and eyeball. The bone models are from a CT scan, the muscle and optic nerve from a MR scan, and other components that cannot be distinguished radiologically are modeled as geometric primitives from anatomic literature. All multi-modal data including the models and images are registered into the same space to form a complete atlas. All structures in the atlas are labeled with their names. An atlas browser is developed for user-friendly manipulation and presentation of the atlas content. Each structure can be turned on or off, rotated, zoomed, or moved, either individually or in unison with other selected structures. Thus, the relationships between different structures can be studied in greater depth. The method developed to build the orbital atlas is general and can be used to create other atlases or to build patient specific geometric models. The orbital atlas may be used for studying the orbital anatomy, as a reference guide for practitioners, and as a base for simulation of orbital surgery.