Estimation of close contact doses to young infants from surface dose rates on radioactive adults.

A general method is given to estimate the dose to an infant held in close contact to a radioactive parent. Calculated values of effective exposure times are given for various radiopharmaceuticals corresponding to a simplified sequence of periods of close contact. When multiplied by a measurement of the dose rate on the surface of an adult, these times can be used to give a quick upper estimate of a close contact dose. This allows a decision whether it is necessary to issue instructions for restricting the duration of close contact to an adult patient, before the patient leaves a nuclear medicine department. Estimates of close contact dose have been made from measurements of surface dose rate using these effective exposure times. Doses to infants from adults who have undergone diagnostic radiopharmaceutical procedures can be kept below 1 mSv without imposing restrictions in close contact. A close contact dose of 1 mSv will be exceeded by activities of 131-I iodide greater than 112 MBq.