In the 1970s, an amazing new technology broke into the medical field. It promised to improve diagnostic accuracy by providing detailed pictures of inside the body. And by and large, it kept its promise. It’s widely accepted that CT scans improve medical diagnoses.
But CT scans have their downsides. They are more expensive than traditional x-rays, largely due to the cost of the equipment. Now, it appears the radiation from the test, up to 50 times greater than a traditional x-ray, may increase the patient’s risk for cancer.
Investigators used data about atomic bomb survivors, who have had more cancers than other same-age Japanese. They calculated the increased risk of the atomic bomb survivors who received radiation in amounts similar to radiation doses from CT scans. Then they applied that risk factor to US populations. If patients in the US who receive CT scans have subsequent cancer at the same rate, as expected, it will lead to an increase of one and a half to two percent in total US cancers.
The investigators believe, “...(D)espite the fact that most diagnostic CT scans are associated with very favorable ratios of benefit to risk, there is a strong case to be made that too many CT studies are being performed in the United States.” They cite as possible examples CT exams for chronic headaches, blunt trauma, and as the primary diagnostic tool for appendicitis in children.
How CT Scans Produce Risk
CT scanners use traditional x-rays, narrowly aimed, and repeated in “slices.” The slices are reassembled by computer software—the “C” stands for computer—to produce clear images. X-rays are high energy radiation, and can knock electrons out of orbit. In the body, this produces ions. A common ion produced is hydroxyl, which can bust up DNA. If a DNA double strand is busted, its natural repair may be faulty, a poor patch-up job, which can affect the normal cell control function, and allow a nest of cancer cells to grow. It may be years before the defective DNA loses control of cell metabolism, so the cancer will not occur until later.
The danger is greater in children because they are smaller, with less mass to dilute the radiation, and because they will usually live longer after a CT scan is done—they have a longer life expectancy because of their age.
What You Can Do
It is always worth discussing it when a CT scan is being considered. Many physicians are not sensitive to the potential downside of CT scans. Studies show that up to 90% don’t know of or don’t believe CT scans can increase the risk of cancer.
Ask your doctor exactly how getting a CT scan will help you. Might it change your treatment? Might it change the expected outcome? If the answers are “No and no,” you need to discuss this more, or get another opinionAsk if another procedure might give the necessary information. Ultrasound images use no radiation at all, and sometimes can give the needed information. MRI (magnetic resonance imaging) also uses no radiation. Traditional x-rays might work, in some cases, with less radiation.
Cut down on your total radiation exposurewhere you can. Ask your dentist if routine dental x-rays have been shown to improve dental health. If she says “No, not really,” as she is likely to, discuss with her why you have to have the unnecessary radiation.
Do not ever let yourself get a routine x-ray of ANY kind without discussingthe advantages and disadvantages with the doctor. Many doctors order routine chest x-rays, just because they always did. (“Routine x-rays” here means those that are ordered not because of a specific symptom or sign, but just as a general screening matter.)
Ask about the age and radiation pattern of the equipmentthat might be used. Newer equipment has less radiation, as does digital equipment.
Source: Computed Tomography — An Increasing Source of Radiation Exposure. New England Journal of Medicine 2007;357:2277-84.
