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Medical Radiation and Cancer, the Risk from CT Scans


In the US, radiation exposure from medical sources has risen 600% in the last three decades, mainly as a result of a dramatic increase in the use of CT scans and other diagnostic tests that involve higher doses of ionizing radiation compared to conventional X-rays. These tests provide great medical benefits but also potential risks, including the risk of radiation-related cancer. The overall public health impact of these trends in medical radiation exposures is not yet known. There are particular concerns about use in children because they are known to be more radiosensitive and radiation doses can be higher.


NCI researchers developed state-of-the-art radiation risk modeling tools and estimated that 29,000 future cancers could be related to the number of CT scans performed in a single year in the U.S. Results from a separate study—the first to directly study the cancer risks after CT scans in children—found that cumulative radiation dose from 2-3 head CT scans (based on current scanner settings) could triple the risk of developing brain tumors and 5-10 head CT scans could triple the risk of developing leukemia. However, these two malignancies are relatively rare, and the actual number of additional cases caused by radiation exposure from CT scans is small.


There is increasing recognition of the potential harms resulting from overuse of diagnostic tests. These studies have been cited by the FDA, American College of Radiology and other professional organizations as evidence of the need for clinical practice to change. The new direct evidence of subsequent cancer risks after CT scans in childhood could result in new guidelines for usage in children and technological innovations to reduce doses.  

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