Pediatric Non-Contrast CT (NCCT) - Contraindications

Absolute contraindications

• None specific to the CT technique itself (unlike MRI, there is no issue with ferromagnetic implants, pacemakers, cochlear implants, etc., since CT uses ionizing radiation, not a magnetic field).
• Pregnancy in a post-menarchal adolescent, when clinically relevant, is generally avoided unless the scan is emergent and benefit outweighs fetal radiation risk - the same principle applied in adults.

Relative contraindications / key concerns in children

1. Ionizing radiation exposure
   • Children are more radiosensitive than adults and have a longer remaining lifespan for radiation-induced malignancy to manifest, so unnecessary or repeated CT scans (especially head CT) carry a higher lifetime cancer risk per unit dose than in adults.
   • This drives the "ALARA" (As Low As Reasonably Achievable) principle and the use of clinical decision rules (e.g., PECARN, CATCH, CHALICE) to avoid scanning low-risk children with minor head trauma. A single head CT delivers roughly 10-20 mGy to the brain, with higher absorbed dose in younger children.
   • Recent evidence continues to focus on minimizing this risk: a 2025 systematic review/meta-analysis in AJNR specifically examined dose-reduction strategies for pediatric head CT (PMID: 40054878), and another 2025 systematic review quantified radiation dose to the eye lens from pediatric brain CT (PMID: 40815377) - both underscore that dose optimization, not scan avoidance alone, is now a major focus.
2. Inability to keep still / need for sedation
   • Young or uncooperative children may need sedation or general anesthesia to obtain a motion-free scan. This is not a contraindication to the CT itself but adds the risks of sedation (respiratory depression, airway compromise) that must be weighed against the diagnostic benefit.
3. Clinical instability
   • An unstable child (airway/breathing/circulation compromise) should be resuscitated and stabilized before transport to CT; scanning an unstable patient without monitoring/support is a practical contraindication until stabilized.
4. Availability of a non-radiating alternative
   • When ultrasound or MRI can answer the clinical question with equal accuracy (e.g., suspected appendicitis, some congenital anomalies, non-emergent intracranial evaluation), these are often preferred in children specifically to avoid radiation, per the Washington Manual of Medical Therapeutics imaging chapter and general radiology practice - The Washington Manual of Medical Therapeutics, p. IMAGING chapter.
5. Low pretest probability of significant pathology
   • For pediatric head trauma specifically, validated rules (PECARN) identify children at low risk (e.g., no vomiting, no severe headache, no non-frontal scalp hematoma in children under 2, normal mental status/GCS 15) in whom CT is not recommended because the risk of clinically important traumatic brain injury is under 0.05%, making the radiation risk outweigh the diagnostic yield.

Practical takeaway