Imaging and Radiation: Helping Patients Make Informed Decisions

Lilian White, MD
Posted on May 12, 2025

Each year, an estimated 691 million x-rays, computed tomography (CT) and nuclear medicine scans are performed in the United States. This accounted for more than 16% of ionizing radiation studies worldwide. On average, people in the United States are also estimated to experience a higher annual dose of radiation at 2.2 millisieverts (mSv) compared with the global average of 0.56 mSv.

For context, radon exposure in homes is one of the primary sources of naturally occurring radiation exposure. The Environmental Protection Agency and the International Commission on Radiological Protection recommend an annual safety limit of 3-10 mSv for radon exposure in homes. Likewise, air travel contributes to radiation exposure: A domestic flight exposes people to 0.5 mSv/hour of atmospheric radiation while at cruising altitude. In comparison, the average radiation dose received by nontarget organs during a full course of cancer treatment is an estimated 298 mSv.

The dose of radiation varies across imaging studies:

●      CT scan of the chest: ~6 mSv

●      CT scan of the abdomen: ~22 mSv

●      Low-dose CT scan of the chest: ~1.5 mSv

●      Chest x-ray: ~0.25 mSv

●      Mammogram: ~3.7 mSv

A recent study evaluated the projected lifetime cancer risks from current CT imaging. The study used a risk model that incorporated patient demographics to project cancer risk from CT scans at 143 hospitals and outpatient facilities. Estimated doses of radiation were calculated for each body part imaged. The estimated dose of radiation was used to approximate the risk of future cancers in the population studied. The study somberly concluded, “If current practices persist, CT-associated cancer could eventually account for 5% of all new cancer diagnoses annually.”

It is important to acknowledge that studies like this rely on risk modeling rather than prospective clinical trials. The primary basis for radiation risk and modeling estimates stems from previous research on atomic bomb survivors. Definitive evidence is still needed to understand the relationship between imaging radiation and long-term cancer risk.

Family doctors can mitigate risk of radiation exposure through personalized patient care and judicious ordering of imaging studies. A 2021 AFP article on appropriate and safe use of diagnostic imaging provides useful guidance and best practices. Unfortunately, insurance-driven testing requirements—such as in preoperative testing—can contribute to unnecessary radiation exposure despite physician discretion. The American College of Radiology (ACR) Appropriateness Criteria may help guide imaging recommendations. Interestingly, eliminating prior authorization denials has not been associated with increased imaging use.

Patient education also plays a valuable role in informed decision-making. Discussing the risks associated with imaging radiation, such as mammography, can help foster shared decision-making and informed consent in clinical practice. Patient education guides such as the ACR radiation dose reference chart may be a helpful resource.