Justifying referrals for paediatric CT.

• The system of radiation protection assumes a linear dose-response relationship with no threshold for low doses and dose rate exposures. This is based on epidemiological evidence at higher doses. • Hence there is a small theoretical risk of carcinogenesis attributable to low doses of ionising radiation. This risk is associated with any diagnostic imaging procedure involving radiation. • Radiosensitivity declines with age, so children are more susceptible to radiation risks than adults. Females are more radiosensitive than males. • The radiation protection system is based on the assumption that radiation risk is cumulative over a lifetime. • For an individual, a justified, optimised computed tomography (CT) scan will result in more benefit than harm. A doctor must justify the necessity for a CT scan before referring an individual for imaging.