NCCT brain isn't "forbidden" outright — it's still used emergently (acute trauma, suspected bleed, hydrocephalus, raised ICP) — but it is used cautiously and often avoided/replaced by other modalities in children for several reasons:

1. Radiosensitivity of the developing brain Children's tissues, including neural tissue, are far more radiosensitive than adults', and they have a longer remaining lifespan for radiation-induced malignancies (leukemia, brain tumors) to manifest. As Grainger & Allison's puts it, "the main limitation of CT imaging is the potential radiation risk, especially in neonates, children and young adults" - Grainger & Allison's Diagnostic Radiology. Rosen's Emergency Medicine also notes girls are more radiosensitive to CT than boys, and pediatric CT use has risen sharply despite this risk.

2. Cumulative dose over a lifetime A single scan's risk is small, but children often need repeat imaging (e.g., shunted hydrocephalus, chronic epilepsy workups), and this cumulative exposure raises the theoretical lifetime cancer risk. Maingot's Abdominal Operations notes CT "can be recommended for children with one caveat" - the radiation "theoretically causes a small increase in the lifetime risk of certain [cancers]."

3. Poor soft-tissue/parenchymal resolution in young children This is a technical, not just a safety, issue. CT has inherently poor gray-white matter contrast, and in infants the brain is incompletely myelinated with high water content, making CT even less able to distinguish normal from abnormal parenchyma. Grainger & Allison's also notes CT use is restricted in children partly because "paucity of body-fat in young children hampers identification of tissue planes." This is why CT is poor at detecting subtle findings like hypoxic-ischemic injury, early infarcts, migration/myelination disorders, or diffuse axonal injury in infants - MRI is far more sensitive for these.

5. Net effect NCCT brain is reserved for emergencies where speed and availability outweigh the radiation concern (acute trauma, suspected acute hemorrhage, acute hydrocephalus/shunt malfunction), while ultrasound (in infants with open fontanelle) or MRI is preferred for non-emergent, detailed, or follow-up brain imaging in infants and children.

A 2025 systematic review (PMID: 40815377) specifically quantified radiation dose to the eye lens from pediatric brain CT scans, reinforcing that dose-reduction and modality selection remain active concerns in pediatric brain CT protocols - consistent with the textbook guidance above, no contradiction found.

If you meant a more specific clinical scenario (e.g., neonatal seizures, suspected NAT/abusive head trauma, hydrocephalus follow-up), let me know and I can go deeper into that specific context's imaging algorithm.