Since the same phantom is used to drive each of the simulators described above, it becomes an ideal tool to test same subject, inter-modality registration. One begins by applying a rigid-body transformation to the phantom before image simulation. Each modality is then simulated using the full battery of options (noise, contrast, slice thickness, etc...) available from the simulators. Afterwards, the registration procedure is applied. Since the rigid body transformation is known a priori, it can be used as a gold standard to test the output of the registration algorithm.