Meta-analysis of cranial CT scans in children. A mathematical model to predict radiation-induced tumors.

OBJECTIVE: We aimed to estimate the risks of radiation exposure from a single head CT scan to children of different ages.

MATERIALS AND METHODS: We constructed a multistate time-dependent Markov model to simulate the course of children exposed to a head CT. The relevant literature was reviewed for probabilities, which were used to calculate tumor types, latencies after exposure and outcomes in the model. Where multiple approximations of the same probability had been reported, meta-analytic techniques were employed to compute pooled estimates. The model was then used to calculate the effect of the radiation exposure on life expectancy and quality of life for children following head CT at different ages.

RESULTS: The tumors likely to be induced by low-level cranial irradiation include thyroid carcinoma (47%), meningioma (34%) and glioma (19%). According to the model, a single head CT is likely to cause one of these tumors in 0.22% of 1-year-olds, 30% of whom will consequently die. The exposure will shorten the life expectancy of all exposed 1-year-olds by an average of 0.04 years and their expected quality of life by 0.02 quality-adjusted life years. The risks of radiation exposure diminish for older children.

CONCLUSIONS: The model predicts that the effective radiation dose from a single head CT is capable of inducing a thyroid or brain tumor in an infant or child. These tumors can severely impact both quality of life and life expectancy. Care should be taken before ordering CT scans in children, particularly in infants and toddlers.