Radiation is an important medical tool. Many people think of radiation as uniformly harmful, but doctors routinely use radiation to promote health. Radiation-emitting pharmaceuticals can help diagnose and treat many diseases and conditions. X-ray exposures can both find life-threatening cancers and help eliminate them. The key to using medical radiation safely and effectively is to use it at the right dose and energy level. NIST physicists maintain and continually improve the nation's standards for radiation measurement so that doctors can harness the power of radiation to improve their patients' health.