Could Medical Imaging Account for 10% of Childhood Blood Cancers?

Imaging decisions for children and adolescents depend on the benefit–risk balance . Published on 17 September 2025 in NEJM , a new study involving 3.7 million people found an association between cumulative radiation reaching bone marrow and hematological (blood and bone marrow) cancer risk that was small but statistically significant . It reinforces using high-dose tests such as CT only when truly necessary and with the lowest reasonably achievable dose (ALARA).

📏 What Does Radiation Dose Mean?

Radiationis invisible energy carried as waves or particles. In medical imaging, it usually comes from X-rays and similar sources and is measured in mGy (milligray) . Dose represents energy transferred to tissues.

⚡ Imaging Using Radiation

• X-Ray: For example, chest X-ray (~0.1 mGy)
• Computed Tomography (CT): For example, head CT (~13.7 mGy), abdominal CT (~15–20 mGy)
• Nuclear Medicine: PET, scintigraphy (injected radioactive material)

🛡️ Imaging Without Radiation

• Ultrasound (US): Uses sound waves without radiation.
• Magnetic Resonance Imaging (MRI): Uses magnetic fields and radio waves without radiation.

🔢 Example Dose Comparisons

• 1 Chest X-Ray: ~0.1 mGy
• 1 Head CT: ~13.7 mGy
• 1 Abdominal CT: ~15–20 mGy
• 30 mGy Exposure: In the study, associated with a 76% increase in cancer risk.

Note: Although individual test doses are low, repeated CT scans increase cumulative exposure.

Study Design

• Cohort: From the US and Canada, 3,724,623 children born in 1996–2016.
• Follow-Up: Total: 35,715,325 person-years (mean 10.1 years/person), ending at cancer/benign tumor, death, insurance termination, age 21 or 31 December 2017.
• Exposure: Medical imaging dose to active bone marrow (mGy).
• Analysis: Continuous-time hazards models with a 6-month lag .

📋 Relative Risk (RR) by Dose Range

🎯 Clinical Implications

• Careful Indication: High-dose tests such as CT require justification .
• Dose Optimization: Pediatric protocols, size-based adjustment and avoiding repeat tests.
• Alternatives: Where appropriate, US/MRI may be preferred.
• Documentation and Communication: Record exposure and communicate risks transparently with parents.

🛠️ 5 Practical Steps

1. Initial Assessment: Is the clinical question clear? Will imaging change management?
2. Choose the Modality: Where possible, US/MRI; if CT is needed, use a pediatric dose protocol.
3. Avoid Repetition: Retrieve/share prior examinations; dose registry.
4. ALARA Training: Periodic education for pediatric and pediatric emergency teams.
5. Inform Parents: Use concrete comparisons such as "One head CT ≈ 13.7 mGy" to explain risk.

❓ Brief Summary for Physicians and Parents

In Brief: As cumulative radiation to children's bone marrow increases, hematological cancer risk measurably rises. The risk is small but significant, making a clear indication and the lowest dose essential.

📚 Source

Smith-Bindman R, Alber SA, Kwan ML, Pequeno P, Bolch WE, Bowles EJA, Greenlee RT, et al.
Medical Imaging and Pediatric and Adolescent Hematologic Cancer Risk. New England Journal of Medicine. Published: 17 September 2025. DOI: 10.1056/NEJMoa2502098