Diagnostic imaging can help accurately diagnose disease and contribute to effective treatment planning, but repeated exposure to radiation can increase risk of developing cancer.

X-rays and CT (computed tomography) scans may play an important role in diagnosis of cancer and other diseases and conditions as well as treatment planning. These diagnostic imaging techniques are painless and non-invasive and can create detailed images of the body in seconds. Both X-ray and CT scan, however, use radiation to produce images, and because exposure to radiation is a known cause of cancer, people who are exposed to large or repeated doses of radiation through diagnostic imaging may have an increased risk of developing cancer.

Concerns about cancer risks associated with diagnostic imaging are increasing as use of imaging, particularly CT scans, is becoming more frequent and widespread. CT scans deliver a higher dose of radiation than standard X-rays—doses may be 50 to 500 times higher. And because exposure to radiation adds up over a lifetime, people who undergo repeated CT scans are likely at a greater risk of developing cancer. Risk is also affected by other factors, including the area of body exposed and the patient’s age, with children being more sensitive.

How much may radiation exposure affect cancer risk?

Studies have indicated that 1.5% to 2% of cancers in the United States may be caused by radiation exposure.

How can risk be reduced?

Radiation exposure and associated cancer risks add up over a lifetime, making it important to use CT scans, as well as X-rays, only when there is a valid medical reason. This means that patients who are healthy and at low risk should not undergo excessive CT scans. As well, patients whose treatment plan is not likely to be changed by the results of a CT scan may want to avoid optional testing. In other words, it’s very important that patients and physicians carefully balance the benefits and risks when deciding whether or not to use a CT scan.

It’s also recommended that other diagnostic technologies be considered in order to reduce use of CT scans. Ultrasound and MRI (magnetic resonance imaging), for example, do not expose the body to radiation and may therefore be considered as alternatives to CT scans and X-rays.

Radiation exposure can also be reduced by adjusting radiation doses so that they are appropriate for the patient’s size. This is especially important in children.