The combination of Single Photon Emission Computed Tomography (SPECT) with Computed Tomography (CT) can give an insight into the body of animals and humans. In CT, X-rays are used to generate cross-sectional images of all parts of the body with a very high resolution. Unfortunately, the CT does not provide functional information. With SPECT, the gamma radiation emitted from certain radioactive isotopes can be measured, and their exact localization can be determined. When these isotopes are bound to specific biologically active molecules, and injected in a patients or animal, SPECT can provide information about functional processes in vivo.