I have to have a bone scan because of scoliosis. can having this give me cancer?

Probably not: A bone scan is done by administering a dose of a radioactive isotope into the blood stream. By itself, this is not harmful. However, low doses of radiation exposure over a prolonged time can lead to cancer, though the amount needed to do this is not really known. As long as you do not need frequent tests requiring radiation exposure, there is little risk from a single bone scan.

No: The bone scan exposes the person to a very small amount of radiation, so small that there has never been any evidence that it causes cancer. In fact, there is some evidence that a small amount of radiation actually is healthy (that's why people living in mountains around granite and at high elevations are frequently healthier than others). The theory is called radiation hormesis.