A PET scanner, which stands for Positron Emission Tomography, utilizes an encircling ring of detectors that record the impacts from gamma rays. These gamma rays are created when an electron and a positron collide inside the body and annihilate each other. This collision in turn release two energetic gamma rays which are emitted in opposite directions. Over a period of time these gamma emissions upon striking the detector are interpreted into an image. Read the entire article here. My favorite part of this picture is the little line pointing to a green explosion inside the man’s head reading “gamma rays created,” because that’s what you want more of inside your head, gamma rays.