Radiation dosimetry for extremity radiographs.

The energy imparted, epsilon, to a patient undergoing an extremity x-ray examination may be obtained from the dose-area product incident on the patient. Values of energy imparted can be subsequently converted into the corresponding effective dose, E, using an extremity specific E/epsilon ratio. In this study, an E/epsilon ratio of 3 mSv/J was used to convert values of energy imparted into the corresponding upper limit of adult effective doses for all types of extremity examinations. A modification factor, based on the patient mass, was employed to determine the corresponding extremity effective doses to pediatric patients undergoing extremity examinations. Representative clinical technique factors for six common extremity examinations (hand, forearm, elbow, ankle, tibia/fibula, knee) were used to determine the dose-area product and the corresponding values of energy imparted. For adult extremity x-ray examinations, values of energy imparted ranged from 55 microJ to 920 microJ, with the energy imparted to 1-y-old patients being a factor of about 20 lower. Upper limits of effective doses for adult extremity x-ray examinations ranged from 0.17 to 2.7 microSv, whereas the corresponding doses to 1-y-old patients were about a factor of three lower.