Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal CT examinations.

Patient doses in paediatric and adult CT examinations were investigated for modern multislice CT scanners by using specially constructed in-phantom dose measuring systems. The systems were composed of 32 photodiode dosemeters embedded in various tissue and organ sites within anthropomorphic phantoms representing the bodies of 6-year-old children and adults. Organ and the effective doses were evaluated from dose values measured at these sites. In chest CT examinations, organ doses for organs within the scanning area were 2-21 mGy for children and 7-26 mGy for adults. Thyroid doses for children were frequently the highest with a maximum of 21 mGy. In abdominal CT examinations, organ doses for organs within the scanning area were 3-16 mGy for children and 10-34 mGy for adults. Effective doses evaluated for children and adults were found to be proportional to the effective mAs of CT scanners, where linear coefficients were specific to the types of CT examinations and to the manufacturers of CT scanners. Effective doses in paediatric chest CT and abdominal CT examinations were lower than those in adult examinations by a factor of two or greater on average for the same CT scanners because of the lower effective mAs adopted in paediatric examinations.