What are the risks of radiation exposure from a computed tomography (CT) head scan in a child?

Radiation Risks from CT Head Scans in Children

Children face significantly higher radiation-related cancer risks from head CT scans compared to adults due to their actively dividing cells and longer life expectancy, but the absolute risk from a single scan remains very low—approximately one excess case of leukemia and one excess case of brain tumor per 10,000 head CT scans over 10 years. 1, 2

Primary Radiation Hazards

The pediatric brain is inherently more radiosensitive than the adult brain because of a larger proportion of actively dividing cells and the longer lifespan available for radiation-induced malignancies to develop. 1, 3

Cancer Risk Quantification

• Epidemiological data demonstrate that cumulative doses of approximately 50-60 mGy from CT scans can triple the risk of leukemia and brain tumors in children. 2
• A landmark cohort study of 178,604 pediatric patients showed that compared to doses <5 mGy, cumulative doses ≥30 mGy (mean 51 mGy) resulted in a relative risk of leukemia of 3.18, and doses of 50-74 mGy (mean 60 mGy) resulted in a relative risk of brain cancer of 2.82. 2
• Despite these relative risk increases, the absolute risk remains small: one excess leukemia case and one excess brain tumor per 10,000 head CT scans in the 10 years following the first scan for children under 10 years. 2

Additional Radiation Hazards

• Radiation exposure to the lens of the eye from head CT increases the risk of cataract development later in life. 1, 3
• Approximately 0.4% of all cancers in the United States may be attributable to radiation from CT studies across all age groups. 1

Risk Minimization Strategies

Clinical Decision Rules to Avoid Unnecessary CT

Use validated clinical prediction rules such as PECARN to identify children at very low risk for clinically important traumatic brain injury who can safely avoid CT scanning. 1, 3

• The PECARN study of 42,412 pediatric patients identified children at very low risk (<1% probability) for clinically important TBI who do not require CT imaging. 1
• Clinical observation before CT decision-making is an effective strategy for reducing unnecessary radiation exposure in children with mild TBI (GCS 14-15). 1, 3
• Every additional hour of emergency department observation time was associated with a decrease in CT utilization rates without delaying diagnosis of significant injuries. 1

Technical Dose Reduction

Implement pediatric-specific, reduced-dose CT protocols following the ALARA (As Low As Reasonably Achievable) principle at all facilities imaging children. 1, 3

• Adaptive statistical iterative reconstruction algorithms have contributed to radiation dose reductions of approximately 20% in trauma patients without compromising diagnostic quality. 1, 3
• The ACR Image Gently® campaign provides specific guidance for minimizing pediatric radiation exposure across all clinical applications. 1

Alternative Imaging Modalities

Consider MRI as an alternative to CT for follow-up imaging when cross-sectional imaging is needed, as it involves no ionizing radiation. 1, 3

• Rapid MRI protocols demonstrate almost perfect agreement (κ = 0.84) with CT for detecting extra-axial hemorrhage and substantial agreement (κ = 0.71) for skull fractures in pediatric head trauma. 4
• MRI is superior to CT for detecting diffuse axonal injury and soft tissue injuries. 1, 4

Critical Pitfalls to Avoid

Never compromise diagnostic image quality in pursuit of dose reduction—optimization means achieving appropriate diagnostic quality at the lowest achievable dose, not dose reduction at any cost. 3

• Inadequate image quality may lead to missed diagnoses or repeat scanning, ultimately increasing total radiation exposure. 3
• Do not apply PECARN clinical decision rules to children with suspected abuse, as this population was excluded from the validation study. 3
• Avoid routine repeat CT scans in mild TBI with negative initial findings unless there is clear neurologic deterioration. 1

Balancing Risk and Benefit

The clinical benefits of CT imaging must outweigh the small but real absolute cancer risks, particularly when CT is the only appropriate diagnostic modality for acute evaluation. 1, 2

• For acute moderate-to-severe TBI, head CT remains the first-line diagnostic test (Class I recommendation) despite radiation concerns. 1
• The radiation risk from a single head CT scan (equivalent to approximately 100-200 chest x-rays) must be weighed against the potentially life-threatening consequences of missed intracranial injury. 1