CT scans do expose patients to ionizing radiation, which can damage cells and potentially increase the risk of developing cancer over time. While the radiation dose from a single CT scan is relatively low, repeated or multiple scans can cumulatively raise this risk, especially in children and young adults who are more sensitive to radiation. The risk is generally small for any individual, but because millions of CT scans are performed annually, the overall number of radiation-induced cancers is estimated to be significant.
CT scans use X-rays to create detailed images of the inside of the body. This process involves ionizing radiation, which has enough energy to remove tightly bound electrons from atoms, creating ions. This ionization can damage DNA in cells, potentially leading to mutations that cause cancer. The amount of radiation from a CT scan is higher than that from a standard X-ray because CT imaging collects multiple cross-sectional images to produce detailed 3D views.
Studies estimate that in the United States alone, tens of thousands of future cancers could be linked to CT scan radiation exposure each year. For example, projections suggest that CT scans performed in a single recent year might be associated with over 100,000 new cancer cases over the lifetimes of those scanned. The most common cancers projected include lung, colon, leukemia, bladder, and breast cancers in adults, while in children, thyroid, lung, and breast cancers are more common. The abdomen and pelvis CT scans contribute the largest share of these projected cancers in adults, whereas head CT scans are more significant in children.
Children are particularly vulnerable because their cells are dividing more rapidly, and they have a longer expected lifetime during which radiation-induced cancers can develop. For instance, children who undergo head CT scans have been found to have a significantly increased risk of blood cancers, with the risk rising with the number of scans received. Infants under one year old are estimated to be about ten times more likely to develop cancer from CT radiation compared to adults.
Despite these risks, CT scans are invaluable diagnostic tools that often provide critical information that cannot be obtained by other means. They help detect tumors, guide treatment, and diagnose serious conditions quickly and accurately. Medical professionals aim to balance the benefits of CT imaging against the small but real risks of radiation exposure. They use the lowest radiation dose possible to achieve the needed diagnostic quality and increasingly rely on newer technologies that reduce radiation exposure.
For pregnant women, CT scans are generally avoided unless absolutely necessary, as radiation could potentially harm the developing fetus. Alternative imaging methods like ultrasound or MRI, which do not use ionizing radiation, are preferred in these cases.
In summary, while CT scans do carry a small risk of causing cancer over time due to radiation exposure, this risk is generally outweighed by the diagnostic benefits when scans are medically justified. The risk is higher with repeated scans and in younger patients, so minimizing unnecessary CT imaging and optimizing radiation doses are important strategies to reduce potential harm.
