White spots show up on a bone scan around the dark spots, which indicate an increased accumulation of radioactive material from the scan. In other words, the white areas surround the dark areas that indicate various medical problems, including cancer and arthritis, depending upon where the dark spots appear. MedlinePlus states that an abnormal bone scan shows hot spots and/or cold spots in comparison to surrounding bone.
A bone scan involves injecting a very small amount of radioactive material into a vein, explains MedlinePlus. The material runs through the blood to the bones, giving off some radiation that is detected by the camera in the scanner.
The Johns Hopkins Medicine Health Library explains that hot spots occur with an increased accumulation of the radioactive material while cold spots occur in areas taking up less of the radioactive material. Hot spots may indicate the presence of conditions such as arthritis, malignant bone tumors, metastatic bone cancer, bone infections, bone trauma not seen on ordinary X-rays, and other conditions of the bone. In fact, doctors primarily use bone scans to detect the spread of metastatic cancer.
Cold spots may show a lack of blood supply to the bone or certain types of cancer, WebMD explains. The site adds that hot spots may point to problems such as arthritis, a tumor, a fracture or an infection.