False-colour scintigram (bone scan) of the human spine and ribs, revealing secondary cancers (metastases) in the vertebrae (backbones), arising from a primary cancer of the prostate gland. A scintigram (gamma camera scan) is a record of radioactive emissions from an isotope (in this case, Technetium 99m) that is selectively absorbed by bone when injected into the body. Gamma ray scintigraphy is frequently used to screen cancer patients for signs of secondary disease, often after their primary cancer has been treated. Here, the metastases appear as the pink and white regions along the spine (centre).