CTSim uses geometrical objects to describe the object being scanned. A phantom is composed of one or more phantom elements. These elements are simple geometric shapes, specifically, rectangles, triangles, ellipses, sectors and segments. With these elements, the standard phantoms used in the CT literature can be constructed. In fact, CTSim provides a shortcut to load the published phantoms of Herman[1] and Shepp-Logan[2]. CTSim also reads text files of user-defined phantoms.
The types of phantom elements and their definitions are taken with permission from G.T. Herman's publication[1].