Radiation dose rates from paediatric patients undergoing 99Tcm investigations.

Infants or children undergoing nuclear medicine investigations may subsequently come into close contact with nurses or parents responsible for their care. In order to estimate the radiation dose to these individuals, and to formulate appropriate recommendations, dose rates were measured at distances of 0.1, 0.5 and 1.0 m from 148 paediatric patients who had undergone one of 12 99Tcm studies. The maximum dose rates of 70, 14 and 5 microSv h-1 at these distances were not greater than the corresponding maximum values found in an earlier study of adult patients. However, the maximum dose rates per unit activity of 0.5, 0.2 and 0.1 microSv h-1 MBq-1 were greater than the corresponding maximum 99Tcm adult values, consistent with a general increase of dose rate per unit activity with decrease of body weight observed in the paediatric measurements. A parent caring for and feeding a young infant is most unlikely to receive a dose equivalent of 1 mSv, and a nurse attending to one young radioactive patient is most unlikely to receive a dose equivalent in a working day of 60 microSv. The data obtained should allow radiation doses to be estimated and appropriate recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.