For those individuals who have needed to undergo some sort of medical imaging test recently, like a CT scan, you probably have heard that there is a slight risk of radiation exposure. This is true of many medical imaging procedures, such as CT scans, X-rays, and nuclear imaging tests.
Since the radiation exposure from medical imaging tests has become a common topic of recent in the medical media, patients have been increasingly concerned about the risks of radiation exposure. Specifically, patients are concerned whether the radiation exposure will increase their risk of developing cancer later on.
So, for patients who might be concerned, and for people who might be undergoing a medical imaging test sometime in the future, we’ll explain what the radiation exposure in medical imaging tests means.
Radiation Exposure: What does it mean?
Radiation can take many forms, as radiation technically means that energy is being radiated or transmitted in the form of rays, waves, and particles. The type of radiation present in the medical imaging tests that people are concerned about is called ionizing radiation.
Ionizing radiation typically implicates the capacity to alter chemical compounds like the ones that make up your body and your DNA. Ionizing radiation that damages DNA can eventually contribute to the development of cancer, which is what makes the radiation exposure in tests like X-rays, CTs, and nuclear imaging tests concerning. MRI and radiation exposure, on the other hand, is almost never concerning as it doesn’t involve ionizing radiation.
Ionizing Radiation and Cancer Risks
Radiation can be measured in multiple ways, such as the Geiger counter (measures radiation in the form of clicks with increasingly loud sounds in accordance to the amounts of radiation present). But, the measurements most useful in determining the radiation impact on human health is the sievert (Sv) and the millisievert (mSv) as it takes the biological effects of radiation into account more directly.
It has been long known that high levels of radiation exposure can increase cancer risks in the future. For instance, we know that children and teens that receive high doses of radiation in the treatments for lymphoma and other cancers are more likely to develop additional cancers later in life. However, there’s not any definite guides as to how much radiation exposure will create a significant risks of developing cancer.
One study, though, examined 25,000 Hiroshima survivors and the long-term risks of radiation exposure from the atomic bomb blasts in 1945. The survivors were grouped for the study because they all experience a similar level of exposure just under 50 mSv. The studies showed that these survivors showed a slightly increased risk of developing cancer, but it was enough of an increase to definitively link it to the exposure.
Imaging Procedures and Radiation
Although it is slightly different from the one group of Hiroshima survivors as they experienced all of their radiation in one dose, it is possible to experience a similar level of radiation from 3-4 CTs, depending on the test. Here’s a table that lists the average effective radiation doses of different medical imaging tests from “Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog” in Radiology.
Medical Imaging Procedure
Average Effective Dose (mSv)
Bone density test - 0.001
X-ray (arm or leg) - 0.001
X-ray (panoramic dental) - 0.01
X-ray (chest) - 0.1
X-ray (abdominal) - 0.7
Mammogram - 0.4
X-ray (lumbar spine) - 1.5
CT (head) - 2
CT (cardiac for calcium scoring) - 3
CT (spine) - 6
CT (pelvis) - 6
Nuclear imaging (bone scan) - 6.3
CT (chest) - 7
CT (abdomen) - 8
CT (colonoscopy) - 10
CT (angiogram) - 16
CT (whole body) - 20+ (varies)
Nuclear imaging (cardiac stress test) - 40.7
So, as you can see in the table the amount of radiation from different tests ranges quite a bit. But, it can still provide some guide to radiation exposure and the increased risk of developing cancer. For instance, one study found that the potential risk of cancer from CT scans in a group of 31,462 patients over 22 years was slight, but present. The study reported that the potential risk of cancer increased 0.7% over their lifetime. But, this number can grow depending on the number of tests, as patients who had over 5 CT scans had an increase of 2.7%-12% depending on how many CT scans they received.
At the end of the day, the risk of radiation exposure from medical imaging tests depend on many things, but seems to be extremely slight, if significant at all. In most cases where your doctor or health care provider prescribes one of these tests, it is because they believe that the overall risks are outweighed by the benefit of the tests. However, in a case where you are concerned, don’t be afraid to bring it up to your doctor or ask about the specific risks of increased radiation exposure!