Radioactivity from medical scans involves exposure to ionizing radiation, which has the potential to damage cells and DNA in the body. This damage can, in rare cases, lead to mutations that increase the risk of developing cancer or other health issues over the long term. However, the level of radiation used in most diagnostic imaging tests is generally low, and the associated long-term health risks are considered small when scans are medically justified.
Medical imaging techniques such as X-rays, CT scans, and nuclear medicine scans use varying amounts of ionizing radiation. For example, a typical chest X-ray exposes a person to about 0.1 millisieverts (mSv) of radiation, roughly equivalent to 10 days of natural background radiation. CT scans deliver higher doses, ranging from a few millisieverts to as much as 16 mSv for abdominal and pelvic scans with contrast dye. Nuclear medicine scans also involve radioactive materials but provide detailed images of organ function, which can be crucial for diagnosing and monitoring diseases.
The human body is naturally exposed to background radiation from the environment, averaging about 3 mSv per year. Medical imaging has increased overall radiation exposure, with medical sources now accounting for about half of the total radiation dose in some populations. Despite this increase, modern imaging equipment and protocols aim to minimize radiation doses using the ALARA principle—keeping radiation “As Low As Reasonably Achievable”—to balance diagnostic benefits against potential risks.
Long-term health effects from radiation exposure in medical scans primarily center on the risk of cancer. Ionizing radiation can cause DNA damage that, if not properly repaired, might lead to mutations and cancer development years or decades later. The risk is cumulative, meaning repeated or high-dose exposures increase the chance of harm. However, the absolute risk from a single scan is very low, and the benefits of accurate diagnosis and treatment planning usually outweigh these risks.
Certain populations may be more sensitive to radiation effects. For example, children and young adults have a higher lifetime risk of radiation-induced cancer because their cells are dividing more rapidly, and they have more years ahead for potential effects to manifest. Women of childbearing age are also a special consideration, as radiation exposure before or during pregnancy may increase risks of miscarriage or birth defects, especially with scans involving the abdomen or pelvis. In such cases, alternative imaging methods that do not use ionizing radiation, like MRI or ultrasound, are often preferred.
Studies have suggested that radiation from medical imaging might contribute to a small percentage of cancers worldwide, but direct causality is difficult to prove because the doses are low and cancer can have many causes. The risk models used to estimate cancer risk from low-dose radiation are based on data from high-dose exposures, such as atomic bomb survivors, and assume a linear no-threshold relationship—meaning any radiation dose, no matter how small, carries some risk.
Healthcare providers carefully weigh the need for imaging against potential radiation risks. Advances in technology have led to more efficient scanners that use lower doses, and protocols are designed to avoid unnecessary scans. Patients are encouraged to keep records of their imaging history to help manage cumulative exposure.
In summary, while radioactivity from medical scans can affect long-term health by slightly increasing the risk of cancer and other radiation-related effects, the risk from individual diagnostic tests is very low. The benefits of these scans in detecting, diagnosing, and managing health conditions generally far outweigh the potential harms when used appropriately. Ongoing research continues to refine our understanding of these risks and improve safety measures in medical imaging.