Where does radiation come from?
We are continually exposed to low levels of natural radiation that do not cause any serious health effects. This background radiation comes from the sun, outer space, and natural radioactive isotopes in the earth, air, and food. Small traces of radioactive atoms are present in the human body, including uranium, thorium, potassium-40, radium, carbon-14, tritium, and polonium. People may also occasionally receive small doses of radiation from common medical procedures, such as dental x-rays.
How much radiation are we exposed to?
The average whole-body radiation exposure in the United States is 0.006 Sv (“sieverts”) per year. This average includes radiation from the environment, medical procedures, occupational exposure, and other miscellaneous sources. The doses required to induce harm are much greater than the average annual exposure. For example, radiation sickness may appear after an acute dose of 1 Sv. This is 167 times greater than the average annual exposure, or 61,000 times greater than the average daily radiation exposure.
How is radiation used in medicine?
Radiation is used in medicine for both diagnostic and therapeutic applications. Whenever radiation is used, the medical benefits it offers far exceed the potential risk of harmful secondary effects.
In all medical settings, unwanted radiation doses are kept as low as reasonably achievable (“ALARA“). In diagnostic settings, this means that radiation dose is kept to the minimum required to yield good images of the disease site. Although low levels of ionizing radiation are produced during x-rays, CT scans, and PET scans, these imaging procedures are invaluable tools for noninvasively finding anatomical abnormalities.
In therapeutic settings, the aim is to deliver an effective dose to a tumor or other disease site while minimizing unwanted dose to surrounding healthy tissues.
According to the National Library of Medicine, approximately 14 million new cancers are diagnosed each year. Radiation therapy is an effective form of therapy, with about 60% of cancer patients receiving some form of radiation therapy sometime over their entire course of treatment. Radiation therapy can be given either alone or in addition to surgery, chemotherapy, immunotherapy, or other forms of cancer therapy.