Nuclear medicine is definitely one of the most important developments in modern healthcare. X-Rays have been in use since the turn of the 20th century, and radiation therapy is a powerful weapon against cancer and certain other medical conditions. It does present certain risks to the patient, but those risks are outweighed by the diagnostic and/or treatment benefits of limited exposure. On the other hand, the healthcare professionals that routinely administer those treatments need to be protected from incidental radiation exposure. This is typically facilitated through lead-lined aprons, walls, and door frames, and radiation shielding doors.
