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Radiation Safety
Demonstration data

Pediatric CT Dose Adjustment

Calculate appropriate CT dose reduction for pediatric patients based on age and weight. Prevent unnecessary radiation exposure.

This tool provides age-based scaling factors to reduce adult CT technique parameters for paediatric patients, who are markedly more radiosensitive and have longer post-exposure lifespans in which stochastic effects may manifest. It operationalises the Image Gently campaign principle of 'child-sizing' CT protocols. The adjustment factors offer a first-order estimate of appropriate dose reduction relative to a standard adult examination.

🧮 Interactive Calculator

📐 Formula

Adult dose × adjustment factor. <1yr: 0.3, 1-5yr: 0.5, 5-10yr: 0.7, 10-15yr: 0.85, >15yr: 1.0

Reference: Image Gently Campaign

When to Use

  • Adapting an adult CT protocol when a dedicated paediatric protocol is unavailable
  • Estimating expected dose reduction when scanning infants and children
  • Educating trainees and technologists on the magnitude of paediatric dose scaling
  • Cross-checking that automatic exposure control output is appropriately lower for a child
  • Supporting justification and optimisation discussions in paediatric imaging governance

How It Works

  • Estimated paediatric technique = adult reference dose multiplied by an age-band adjustment factor (<1yr: 0.3, 1-5yr: 0.5, 5-10yr: 0.7, 10-15yr: 0.85, >15yr: 1.0)
  • The factors approximate the reduced body diameter and attenuation of younger children, which permit lower tube current-time product (mAs) and/or tube voltage (kVp) while maintaining diagnostic image quality
  • In practice, dose reduction is achieved primarily by lowering mAs, reducing kVp (e.g. 80-100 kVp in small children), and using automatic tube current modulation
  • The scaling is a coarse age surrogate; weight- or diameter-based (effective diameter) adjustment is more accurate because children of the same age vary widely in size
  • These factors adjust technique, not the k-factor used to convert DLP to effective dose, for which paediatric-specific conversion coefficients are required

Interpreting the Result

  • An infant under 1 year may require only ~30% of the adult dose, whereas an adolescent over 15 approaches full adult technique (factor 1.0)
  • A resulting technique that does not scale down for a small child signals a protocol error and potential overexposure
  • Because risk per unit dose is higher in children, even modest reductions yield meaningful lifetime risk benefit
  • Adequate diagnostic image quality, not the lowest possible number, defines the correct dose; excessive reduction producing non-diagnostic images necessitates a repeat scan and net dose increase
  • Weight or effective diameter should override age banding whenever the child is unusually small or large for age

Limitations & Pitfalls

  • Age is a weak surrogate for body size; two children of identical age may differ substantially in attenuation, making weight/diameter-based methods preferable
  • Fixed multipliers do not account for anatomical region, indication, or the specific noise requirements of the diagnostic task
  • The factors do not capture modern dose-reduction technology (iterative reconstruction, organ-based modulation, low-kVp techniques)
  • Over-aggressive reduction risks non-diagnostic studies and repeat imaging
  • Not a substitute for validated, vendor- and scanner-specific paediatric protocols or size-specific dose estimates (SSDE)
  • Neonatal and premature infants may need protocol considerations beyond simple linear scaling

References

  • Image Gently Alliance: Development of Pediatric CT Protocols and The ALARA Concept in Pediatric CT
  • AAPM Report No. 204: Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT Examinations
  • ACR-SPR Practice Parameter for the Performance of Pediatric Computed Tomography (CT)
  • Strauss KJ et al. Image Gently: Ten Steps You Can Take to Optimize Image Quality and Lower CT Dose for Pediatric Patients. AJR 2010
  • European Commission Radiation Protection No. 154: European Guidelines on Radiation Protection in Paediatric Radiology

⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.