PET, or positron emission tomography, is an imaging tool used in nuclear medicine to observe the process of metabolism in a patient. PET scanners work with a tracer that moves through the body on a molecule that is active within the metabolic chain, thus allowing the visualization of the processes. Computer analysis is responsible for creating the final images, and certain PET scans will work in tandem with CT scanners to create full 3D images. Depending on the tracer type, the system will create imaging of different metabolic processes. They have a high operating cost, but they are helpful with many diagnoses.