Single photon emission computed tomography (SPECT) allows the user to obtain a threedimensional (3D) representation of the patient’s in vivo radiopharmaceutical distribution. Planar nuclear imaging leads to a twodimensional (2D) image of a 3D object. In some cases, it can be difficult to detect or localize a certain feature due to the ambiguity introduced by background activity in the overlying and underlying tissue. Conversely, SPECT allows the 3D object to be represented as a series of thin, tomographic slices. This can lead to a substantial increase in image contrast that can greatly improve the ability to detect small features. Due to the 3D nature of SPECT, it can also greatly improve one’s ability to localize these features. In addition, improved contrast can lead to an enhanced quantitative capability that can be of great value for both clinical and research purposes. For all of these reasons, SPECT has become an essential medical imaging modality over the past 30 years.