A PET scan, or Positron Emission Tomography scan, is a medical imaging technique that helps doctors see how organs and tissues are functioning in the body. It uses a small amount of radioactive material, which is injected into the bloodstream. This material emits positrons, allowing the scanner to create detailed images of areas where the material is absorbed, helping to identify diseases like cancer or Alzheimer's. During a PET scan, patients lie on a table that moves through a large, doughnut-shaped machine. The procedure is painless and usually takes about 30 minutes to an hour. After the scan, doctors analyze the images to make informed decisions about treatment or further testing.