A bone scan is a technique to create images of bones on a computer screen or on film. A small amount of radioactive material is injected and travels through the bloodstream. It collects in the bones, especially in abnormal areas of the bones, and is detected by special instrument called a scanner. The image of the bones is recorded on a special film for permanent viewing. Bone scans are used for the detection and monitoring of disorders affecting the bones, including Paget’s disease, cancer, infections, and fractures. Bone scanning is also helpful in evaluating joint diseases. Bone scanning can be used to detect and measure the activity of joint disease.