A scintillator is a material that emits light when it interacts with radiation. Some synonyms for scintillator include luminophore, radioluminescent material, radiation detector, and detector crystal. Certain types of scintillators are also known as phosphors or luminescent materials. Scintillators are commonly used in medical imaging, such as in positron emission tomography (PET) scans, as well as in various types of radiation detectors, such as geiger counters. Different materials are used as scintillators depending on the type of radiation being detected and the sensitivity required for the application. Some commonly used scintillator materials include sodium iodide, cesium iodide, and gadolinium oxysulfide.