What should be discussed with parents regarding the increased cancer risk from radiation exposure during a computed tomography (CT) scan of the head?

Communicating Radiation Risk from Head CT to Parents

When discussing head CT radiation exposure with parents, explain that while there is a small increased cancer risk (approximately 1 additional cancer per 10,000 head CT scans in children), the immediate clinical benefit of identifying serious brain injury almost always outweighs this very small long-term risk, and most parents (90%) want to be informed of this risk before proceeding. 1, 2, 3

Key Points to Communicate

The Actual Risk in Context

• A head CT scan delivers approximately 2-4 mSv of radiation, equivalent to about 100-200 chest x-rays 1
• For children under 10 years old, one excess case of leukemia and one excess case of brain tumor per 10,000 head CT scans is estimated to occur in the 10 years following the scan 2
• Cumulative doses of 50-60 mGy can approximately triple the baseline risk of leukemia and brain tumors, though these cancers remain relatively rare even with this increase 2
• Children are at higher risk than adults because they have more actively dividing cells and a longer lifespan during which radiation-induced tumors can develop 1

Framing the Discussion

Use clear, balanced language that acknowledges both risks and benefits:

• Emphasize that ionizing radiation from CT scans has been classified as a carcinogen by the World Health Organization and other international health organizations 4, 1
• However, explain that for almost all patients, the adverse health consequences of refusing a needed medical procedure far outweigh any potential radiation-associated risks 4
• The cancer risk is very small in absolute terms, but real—it is not theoretical 2, 5

What Parents Want to Know

• Research shows that only 46.8% of parents are aware of the potential increased lifetime malignancy risk from CT before being informed 3
• Approximately 90% of parents want to be informed of potential malignancy risks before proceeding with imaging 3
• After risk disclosure, willingness to proceed with recommended CT decreases from 90.4% to 69.6%, but only 5.6% would refuse the scan entirely 3

How to Present the Information

Recommended Communication Approach

While visual formats are recommended by best practices to enhance comprehension without bias, current practice shows that radiation risks are most commonly communicated using text format. 4

• Consider using simple numerical comparisons: "About 1 extra cancer case per 10,000 children scanned" 2
• Avoid using effective dose calculations and the Linear No-Threshold (LNT) model to predict population-level cancer deaths, as these predictions are highly suspect and can create substantial public anxiety 4
• Do not multiply large populations by small risk values to generate alarming numbers of "cancer deaths"—this approach is not supported by hard data 4

Address Uncertainty Honestly

• Explain that the cancer risk estimates come primarily from studies of atomic bomb survivors exposed to much higher doses, and extrapolating to lower CT doses involves uncertainty 4
• Note that it is virtually impossible to detect radiation-induced cancers at doses less than 100 mSv in a population, even if such an increase exists, because they cannot be differentiated from naturally occurring cancers 4
• Radiation-induced cancers typically do not occur until 1-2 decades or longer after exposure 4

Risk Mitigation Strategies to Discuss

Dose Reduction Efforts

• Reassure parents that radiation doses are kept as low as reasonably achievable (ALARA principle) while maintaining diagnostic quality 1, 2
• Technological advances in CT scanning have helped reduce radiation doses significantly compared to scans performed a decade ago 1, 5
• Reducing the highest 25% of doses to the median could prevent 43% of projected radiation-induced cancers 6

Clinical Decision Tools

• For children with mild traumatic brain injury, clinical decision rules like PECARN can identify children at very low risk who can safely avoid CT scans 1
• Alternative imaging procedures that do not involve ionizing radiation (such as MRI or ultrasound) should be considered when appropriate 2

Common Pitfalls to Avoid

• Do not minimize or dismiss parental concerns—the risk is small but real, and parents have a right to informed decision-making 2, 3
• Avoid creating excessive fear—media-induced fear of radiation has caused some patients to refuse needed medical procedures, which poses far greater health risks 4
• Do not use inconsistent risk communication—variability in how risks are presented can affect decision-making, especially among parents with lower health literacy 4
• Avoid discussing population-level cancer predictions—these are provocative, garner media attention, create anxiety, and are potentially dangerous 4