Radiation is used in medicine, for example in X-rays, scans with radioactive tracers and radiotherapy. The benefits to the patient usually outweigh the risks, but the dose must still be limited. A patient is given the smallest dose that gives the information or treatment needed, and scans are only done when necessary. Radiotherapy beams are aimed at the tumour to limit damage to healthy tissue.
Tracers are chosen with a short half-life so that their activity falls quickly, which means the total dose received by the patient is smaller.
Medical staff such as radiographers are at greater risk than a patient, because they are exposed many times over many years and their exposure builds up. To reduce it they stand behind a lead screen or leave the room during an X-ray, keep their distance, limit the time they spend near sources, and handle sources with tongs. They wear a dose badge to monitor how much radiation they have received, and there are legal limits on the dose staff may receive.