Effective dose in paediatric computed tomography.

There is limited data currently available for making dose and risk assessments for paediatric patients undergoing computed tomographic examination. A method has been developed to correlate the risk-related quantity, effective dose, to the more simply derived quantity dose-length product. This involved scanning a series of paediatric anthropomorphic phantoms containing thermoluminescent dosimeters to measure effective dose for scans of various anatomic regions. The quantity effective dose per dose-length product was calculated and plotted as a function of patient size. This showed a simple exponential relationship, and equations of fit were derived to enable the calculation of effective dose for a patient of any size. Measurements carried out on a second scanner and for alternative scan volumes indicated that the method could be generally utilized.