see also: [[radiation in pregnancy and diagnostic imaging]] see: [Medical Imaging and Pediatric and Adolescent Hematologic Cancer Risk (2025) - NEJM](https://www.nejm.org/doi/full/10.1056/NEJMoa2502098) - [bookends](bookends://sonnysoftware.com/ref/DL/270328) > Notes from Rose, Emily, Easter, Joshua S. Practice changing papers: A 2025 review of pediatric emergency medicine." American Journal of Emergency Medicine. ### Overview - Children are more radiosensitive than adults and have longer life expectancy leading to a [higher lifetime cancer risk per mGy of exposure](https://pubmed.ncbi.nlm.nih.gov/39095613/)[^1]. - Haematologic cancers are the most common cancer from radiation sequelae. - Imaging “As Low As Reasonably Achievable, ALARA” in children is a campaign to minimise radiation exposure while maintain diagnostic quality and procedural safety. - The American College of Radiology recommends that radiation doses from CT be "as low as reasonably achievable." - This approach includes both justification (ensuring necessary and appropriate imaging) and optimisation (utilising the minimal radiation dose by limiting scan coverage, adjusting CT parameters based on patient size and indication, using weight-based protocols and utilizing alternative methods such as ultrasound and MRI when possible). - These principles can decrease the need for CT imaging by **8%**. - The benefits of an indicated CT typically justify the associated risks. ### Study - Large **retrospective cohort study** examining the association between cumulative ionizing radiation exposure from medical imaging and the risk of hematologic cancers in children and adolescents. - **\> 3.7 million children** born between 1996 and 2016 in six United States health care systems and Ontario, Canada were included with >35 million person-years of follow up (mean 10.1 years per child). - Children were followed from birth until cancer diagnosis, death, end of health coverage, age 21, or the end study date. - Doses to active bone marrow were estimated for all imaging exams with lagged exposure calculations to avoid reverse causation (i.e. imaging due to undiagnosed cancer symptoms). ### Results - In the evaluation of the **2961 hematologic cancers diagnosed in the study population**, there was *a clear radiation dose related linear response rate demonstrated*. - The relative risk of haematologic malignancy vs. 0 mGy increased with cumulative dose: 1.16 (0–1 mGy), 1.41 (1–5 mGy), 1.82 (15–20 mGy), 3.59 (50–100 mGy), 5.64 (≥100 mGy) (table below). - Excess RR per 100 mGy: 2.54 for all cancers ( P < 0.001). - A single head CT, the most commonly performed study, exposes a child to **mean bone marrow dose of 2–13 mGy of radiation**[^2]. - For comparison, a single transatlantic flight exposes individuals to 0.01–0.08 mGy, and a typical single view chest radiograph to 0.02–1 mGy. - In the population-attributed risk, **10.1% of cancers were linked to imaging**. - Interestingly, the association between radiation and cancer risk did not vary based on the age of exposure. |Radiation Exposure (mGy)|Head CT equivalent|Relative Risk of Hematologic Cancer| |---|---|---| |1–5|~1/3|1.41| |15–20|1.5|1.82| |50–100|4–7|3.59| |≥100|>7–8|5.64| ### Discussion - Though absolute risk of each imaging test is low, there is a clearly demonstrated cumulative effect. - Children requiring repeated imaging for chronic conditions face compounded risk from cumulative radiation exposure. - The **mean cumulative radiation dose was 24.5 mGy in those who developed hematologic cancer** (compared to the *14.0 mGy mean* in all children). - The excess cumulative incidence of haematologic cancers by age 21 was 25.6 per 10,0000 in children exposed to ≥30 mGy and 40.8 per 10,000 in those exposed to ≥50–100 mGy. - 1–5 mGy increases hematologic cancer risk by 41%. 50–100 mGy increase the risk by 300%. One unnecessary pediatric CT was associated with a 1 in 2000–4000 lifetime cancer risk. ### Study reflections - The strength of this study is that it includes the largest representative cohort with comprehensive imaging data from birth, and the investigators performed detailed patient-level reconstruction of radiation exposure. - There is potential to underestimate cancer diagnoses (this was mitigated by reviewing national cancer registries). - Additionally, the follow up only to age 21 likely underestimates lifelong risks. - Finally, this study examined only hematologic cancers and did not include other forms of cancer. > [!key points] Takeaway > This is another study showing there are tangible risks associated with imaging, particularly CT acquisition in children. Emergency physicians should be thoughtful in ordering each imaging study, particularly in a child with risk for cumulative exposure. Hospitals should consider creating collaborative evidence-based protocols to minimize radiation, incorporating non-radiating imaging alternatives as well as pediatric weight-based radiation scaling ![[Pasted image 20260408145110.png]] ![[Pasted image 20260408145130.png]] ![[Pasted image 20260408145157.png]] [^1]: Granata C., Sofia C., Francavilla M., et al.: Let's talk about radiation dose and radiation protection in children . Pediatr Radiol 2025; 55 (3): pp. 386-396 [^2]: McCollough C.H., Bushberg J.T., Fletcher J.G., Eckel L.J.: Answers to common questions about the use and safety of CT scans . Mayo Clin Proc 2015; 90 (10): pp. 1380-1392.