Guide to Radiation Safety in Medical Testing

Radiation safety in medical testing has been a hot media topic. More imaging tests that use radiation are available than in the past, and though the risks are typically minimal, they bear consideration. However, it’s also important to note that these imaging tests allow doctors to see the body's internal structures in ways that previously were not possible. Many of today’s lifesaving and life-improving treatments could not be delivered without the advancements made in medical imaging.

Radiation in medical testing

Radiation is energy that travels in waves and is all around us. The radiation used in medical imaging is a type with charged particles in the atom called ionizing radiation. This type of radiation can be beamed at or placed in your body, passing through, absorbed, or reflected by different tissues. The amount of radiation that passes through or bounces back from tissues in the body can be translated into images and allows doctors to see bones, organs, blood vessels, and other structures in the body to see if they’re healthy or diseased. Think, for example, of an X-ray, the oldest form of medical imaging used in various forms for more than 100 years.

Modern radiation imaging tests include X-ray, computed tomography (CT) scans, angiography, nuclear stress testing, and radionuclide scanning. These imaging tests and others have revolutionized medicine and have largely made exploratory surgery (using surgery to identify disease) obsolete.

Radiation doses by type of test

Radiation occurs naturally all around us. We are constantly exposed to radiation from outer space, from elements in the soil, and from other natural and artificial sources. The human body even emits radiation because of certain forms of potassium and carbon. All of this radiation is referred to as background radiation. Understanding how much radiation each of us is exposed to in a year just through daily living can help provide context for radiation amounts from medical tests.

Radiation dose is measured with a unit called a millisievert (mSv). While amounts of background radiation vary depending on where you live, the average dose per year in the United States is 3 mSv.

Concern about radiation doses

Ionizing radiation exposure can cause several health problems. It can increase a person’s lifetime risk of cancer. Additionally, it can result in tissue damage if one area of the body receives a high dose all at once. A third concern is that radiation exposure can harm a fetus if a pregnant woman is exposed. (If you are or may be pregnant, it’s important to notify your doctor before any tests using radiation are performed.)

According to the U.S. Food and Drug Administration (FDA), a CT scan, for example, of some portion of the body resulting in a 10 mSv dose is believed to increase the risk of fatal cancer by 1 in 2000. The risk of fatal cancer in the U.S. overall is 1 in 5. So, while the CT scan will raise cancer risk, it does so at a very small rate compared to the existing risk. Another way of thinking about it is that the CT scan dose is less than what the average American will be exposed to from background radiation over four years.

However, while one test that uses radiation may not raise cancer risk substantially, cumulative lifetime radiation dose matters. The risk for cancer increases as a person is exposed to radiation over the years and a lifetime, not just in single instances of exposure.

If you have already had several radiation-based imaging tests in the past (X-rays, CT scans, etc.) or other tests are being planned for the future by your other healthcare providers, you should make sure your doctor is aware of this. You may also want to keep a list of tests you’ve undergone as part of a personal medical history file that you can keep at home for reference.

Safety measures to reduce radiation risk

The safety measures to reduce your radiation dose during a test vary according to the test. Typically, these safety measures include shielding to limit radiation exposure to the area of the body under study and monitoring of the dose that’s being given to be sure it’s within acceptable limits.

Additionally, the Society for Cardiovascular Angiography and Interventions (SCAI) has issued recommendations (“Radiation Safety Program for the Cardiac Catheterization Laboratory”) for best radiation practices for interventional cardiologists, the specially trained doctors who perform catheter-based procedures such as angioplasty and stenting in a hospital’s catheterization (cath) laboratory. These recommendations and other professional standards guide the ordering and use of diagnostic tests.