A bone scan is a nuclear imaging test physicians use to look for areas of increased or decreased bone metabolism. Physicians often use this study in conjunction with other tests to diagnose bone infections, cancer or other degenerative bone diseases.
During a bone scan, a technician injects a radioactive material into a vein. The substance travels throughout the bloodstream, organs and bones. After the substance wears off, it gives off radiation the imaging equipment can pick up. The National Institutes of Health explains that bone scans performed to look for an infection in the bone involve a three-phase scan. Technicians take pictures just after the technician injects the radioactive material and again three to four hours later, after the material has collected in the bones. If a physician is using the bone scan to detect cancer in the bones, the technician takes images only three to four hours after the injection of the radioactive material.
Abnormal results do not necessarily mean that a person has a bone disease. Abnormal results mean that the radioactive material did not distribute evenly throughout the bone. The radiologist looks for darker spots called hot spots as well as lighter spots called cold spots to look for places where the radioactive material may have accumulated. While a bone scan is sensitive to bone abnormalities, it is less helpful in determining the cause of the abnormality, according to MayoClinic.com.
When a radiologist notices hot spots on the images, he often recommends further testing to help determine the cause. A physician may order blood tests other more detailed imaging studies such as computerized tomography or magnetic resonance imaging, or a sample of bone tissue called a biopsy in order to help narrow down the actual cause of the hot spots on the images.
A bone scan can often help physicians diagnose bone infections, or osteomyelitis, bone tumors and fractures. Bone scans are also helpful in looking for determining whether cancer has metastasized or spread to the bones. Results can show abnormal bone cells and advanced arthritis as well as help determine the cause of bone pain.
Because technicians must inject radioactive material into the vein, physicians do not recommend the test for women who are pregnant or nursing. If a woman must have the test while breastfeeding, the National Institutes of Health explains that she should pump the breast milk but throw it away for at least two days. Risk of reaction to the radioactive material is rare but may cause rash, swelling and a severe anaphylactic reaction.