Paediatric Imaging Guidance
CT/MRINICE NG232 (May 2023)RCR/SCoR/RCPCH2017, revised 2018RCR iRefer2017, continuously updatedIR(ME)R 2017SI 2017/1322v2.0 · March 2026
Routine
EDInpatientOutpatient
Radiation Sensitivity in Children
— ALL of the following must be met
- ALARA (As Low As Reasonably Achievable) principle mandatory for all paediatric exposures — children have up to 10-fold higher lifetime attributable cancer risk compared to adults for the same effective doseIR(ME)R 2017 Reg 11
- Radiosensitivity is highest in rapidly dividing tissues — thyroid, breast buds, gonads, and bone marrow are particularly vulnerable in children
- Every paediatric CT must be individually justified with a higher threshold of benefit than for adults, given the increased lifetime riskIR(ME)R 2017
- Non-ionising alternatives (ultrasound, MRI) must be actively considered before CT in all paediatric casesRCR iRefer
Age-Specific CT Protocols
— ALL of the following must be met
- IV contrast dose is weight-based: typically 1–2 mL/kg of iodinated contrast (300 mgI/mL), maximum dose should not exceed adult dose
- Field of view (FOV) must be adapted to body habitus — use the smallest FOV that covers the clinical area of interest to maximise spatial resolution and reduce scatter
- Reduce kVp for smaller patients: 80 kVp for neonates/infants, 100 kVp for children <40 kg, 120 kVp only for adolescents approaching adult size
- Use automatic tube current modulation (ATCM) with weight/age-appropriate reference mAs — typical paediatric protocols use 30–70% lower mAs than adult protocols
- Single-phase acquisition is standard — multi-phase CT is rarely justified in children and must have explicit senior radiologist approval
Non-Accidental Injury (NAI)
— ALL of the following must be met
- Skeletal survey is the first-line imaging investigation for suspected NAI in children under 2 years — CT should not replace the skeletal surveyRCR/SCoR/RCPCH
- CT head is mandatory for all children under 1 year with suspected NAI, even without neurological signsRCR/SCoR/RCPCH
- Follow-up skeletal survey at 11–14 days recommended to identify healing fractures not visible on initial imagingRCR/SCoR/RCPCH
- Refer to RCR/SCoR/RCPCH 'Radiological Investigation of Suspected Physical Abuse in Children' for full imaging algorithmRCR/SCoR/RCPCH
- Safeguarding team must be notified before imaging — all NAI imaging requests should be discussed with a consultant paediatric radiologist where available
CT Head — Differences from Adult Criteria
— ALL of the following must be met
- Lower GCS threshold for immediate CT: GCS <14 in children (vs ≤12 in adults), or GCS <15 in infants under 1 yearNICE NG232 (May 2023)
- Dangerous mechanism thresholds differ: fall >3 m in children (vs >1 m in adults); high-speed RTA; high-speed projectile impactNICE NG232 (May 2023)
- Vomiting threshold: ≥3 discrete episodes in children (vs >1 episode in adults)NICE NG232 (May 2023)
- Tense fontanelle in infants is an additional indication for immediate CT not applicable to adultsNICE NG232 (May 2023)
- Bruise, swelling, or laceration >5 cm on the head in infants under 1 year — immediate CT indication unique to paediatricsNICE NG232 (May 2023)
MRI as Preferred Modality
— ALL of the following must be met
- MRI delivers no ionising radiation and is the preferred cross-sectional modality in children where clinically appropriate and timely access is availableRCR iRefer
- MRI is preferred over CT for non-urgent brain imaging in children (e.g., epilepsy, developmental delay, headache) — CT only where MRI is unavailable or clinically urgent
- MRI is the modality of choice for paediatric spinal pathology including cord compression, tethered cord, and spinal dysraphism
- MRI is preferred for musculoskeletal soft tissue assessment, bone marrow pathology, and joint internal derangement in children
Sedation and Anaesthesia for MRI
— ALL of the following must be met
- Children under 5–6 years typically require sedation or general anaesthesia (GA) for MRI due to inability to remain still for scan duration (20–60 minutes)
- Feed-and-sleep technique may be adequate for neonates and young infants (under 3–6 months) — avoids sedation/GA risks
- GA carries small but non-negligible risk — weigh the clinical benefit of MRI against anaesthetic risk, particularly for repeat imaging
- Sedation/GA for paediatric MRI requires appropriately trained anaesthetic staff, MRI-conditional monitoring equipment, and recovery facilities
- Standard fasting guidelines apply: 6 hours solids, 4 hours breast milk, 1 hour clear fluids — confirm local policy
Diagnostic Reference Levels (DRLs) for Paediatric CT
— ALL of the following must be met
- National DRLs for paediatric CT are published by PHE/UKHSA and must be used as benchmarks — departments should audit against these regularly
- Paediatric DRLs are stratified by weight bands (typically 5 kg, 10 kg, 20 kg, 30 kg, 50 kg) rather than age alone
- Example paediatric DRLs for CT head: CTDIvol ~30 mGy (neonate), ~40 mGy (1 year), ~50 mGy (5 years) — significantly lower than adult DRL of ~60 mGy
- If DRL is consistently exceeded, a formal investigation and protocol optimisation is required under IR(ME)R employer's proceduresIR(ME)R 2017
Notes
Warning
Children have up to 10-fold higher lifetime cancer risk from radiation than adults — always consider non-ionising alternatives first
Alert
Do not apply adult CT head criteria to children — paediatric GCS thresholds and mechanism criteria differ significantly
Information
Weight-based protocols are essential — never use adult default CT parameters for paediatric patients
Warning
For suspected NAI, skeletal survey must precede CT — follow RCR/SCoR/RCPCH guidance
Information
MRI is preferred over CT for non-urgent paediatric imaging wherever clinically appropriate
Change Log
v2.02026-03-08New cross-cutting paediatric guidance