A 45-day-old baby can have a head CT if the condition requires it, and occasional head CTs have no significant side effects on the baby. Head CT is mainly used to check for intracranial hemorrhage, masses, parenchymal brain lesions and other symptoms in infants, and there may be a certain amount of radiation, but this amount of radiation, if not prolonged exposure, will not have any obvious effect on the body. 45-day-old infants who are in need of medical conditions can be diagnosed using head CT under the guidance of a doctor. Because 45-day-old infants are relatively young, the doctor may inject a small dose of sedative into the infant during the head CT so that the infant will not cry during the examination, which may affect the results.