Assessment of the problem: pediatric doses in screen-film and digital radiography

Abstract

In diagnostic radiology, radiation exposure measures the amount of radiation at a given location in an x-ray beam, dose measures the energy deposited in a specified absorber, and equivalent dose quantifies the biological harm expected from this deposited energy. The effective dose attempts to account for the energy deposited in all irradiated organs as well as their relative radiosensitivity, and is the best available descriptor of the stochastic patient risk. Effective doses can be estimated from measures of the radiation beam incident on the patient as either entrance skin dose or dose-area product in conjunction with appropriate conversion coefficients. These effective dose-conversion coefficients are influenced by the patient size, exposed body region, x-ray beam quality, and x-ray beam area. We present values of skin dose, dose-area product, and effective dose for common examinations in pediatric patients whose size ranges from the newborn to adolescents. In screen-film radiography, the system speed defines the amount of radiation required to generate a satisfactory radiographic film density. Changing the screen thickness normally modifies the speed of screen-film systems, which affects the system resolution but not the level of image noise (mottle). By contrast, digital systems have a fixed resolution but can operate satisfactorily over a wide range of receptor dose, with the amount of noise in the resultant image being inversely related to the amount of radiation used. To ensure that patient doses are kept as low as reasonably achievable (ALARA), it is essential that digital receptor doses be monitored to ensure they stay constant. It is also important that protocols in digital radiography are specific for the imaging task to be performed, and use no more radiation than needed to achieve a satisfactory diagnosis.