A single CT scan routinely used to evaluate patients for heart disease emits more than 150 times the amount of radiation that comes from a single chest X-ray. Radiation can damage the DNA genetic material in cells, kill some cells, and cause increased expression of genes involved in the repair or death of cells (Journal of the American College of Cardiology [Cardiovascular Imaging], published online July 22, 2015). In 2007, the National Cancer Institute predicted that 29,000 future cancer cases could be linked to the 72 million CT scans performed in the U.S. in that year alone.
How CT Scans May Cause Cancer
Radiation can damage DNA, so it can cause normal cells to forget to die and then they become cancerous. Normal cells go through a certain amount of doublings and then die. For example, normal skin cells live 28 days and then die. Normal cells lining your lips live 24-48 hours and then die. Red blood cells live 120 days and then die. This is called apoptosis and is necessary. Cancer cells do not die on schedule. Your immunity is supposed to search out and destroy these abnormal cells that do not die, but sometimes they continue to grow (as in a tumor), and may spread to other parts of your body. For example, breast cancer does not kill as long as it is just in the breast, but breast cancer cells can travel to your brain, bones, liver, lungs and so forth, where they destroy essential functions and kill you.
CT scans are far more dangerous than X rays because they produce so much more radiation. Sonograms use sound waves which are harmless. MRIs do not produce radiation, but they are often not used because they are more expensive. If your doctor recommends a CT scan, ask if there is a safer alternative.