Before the advent of advanced medical imaging technologies, the only way to see inside the human body was to cut it open in surgery. Now PET scans, MRI's, X-rays and other imaging technologies help doctors see from the inside out.
A typical PET scanner is a large machine with a hole in the middle, shaped like a giant doughnut. It contains many rings of camera detectors. Once a patient has been injected with a radioactive substance, he or she lies on a sliding metal slab, which moves into the hole to begin the scanning process. The emitted radiation is detected by the cameras and that data is transmitted to a computer. The computer uses complicated mathematical formulas to arrange the data into a map of that region of the body, arranged according to different colors of degrees of brightness. For instance, more of the radioactive substance will accumulate in cancerous tissue than in normal tissue, so any cancerous areas will appear brighter on PET images. This is known as a "hot spot": cancerous tissue burns energy at a faster rate than normal tissue, a clear indication of malignancy.
PET is used to produce images of blood flowing through the body from the heart to detect heart disease. It can show how glucose (a primary energy source for the body) is broken down and used by the brain. PET scans of the brain are used to study patients with unexplained memory loss; they may have brain tumors or suffer from an undetected seizure disorder.
Positron Emission Tomography (PET) relies upon radioactive substances injected into the patient's body. A PET detects the gamma rays given off as radiation when atoms from the radioactive substance collide with atoms that make up body tissue. Then this data is used to compile an image of the area being scanned.