Explain how a gamma camera works to produce an image.

A gamma camera works in the following way: gamma rays, which are extremely high-energy light particles that can penetrate the human body very deeply, but also can cause dangerous cellular mutations, are produced by a sample of contained radioactive material. The gamma rays are aimed toward a specific area of the human body (the place intended to be imaged and examined), and the gamma rays penetrate the tissue.
Because the density of tissues and materials inside the human body varies (calcium is more dense than water, muscles are denser than fat, etc.), the gamma rays get scattered or absorbed at different rates depending on what they are passing through. On the other side, a crystal plate of sodium iodide doped with thallium (a mineral that interacts strongly with gamma rays) is used to capture the image. Based on the amount of gamma rays that have penetrated, a clear image is formed that shows the varying densities and structures present in the area.