Measuring and minimizing the radiation dose to nuclear medicine technologists

Nuclear medicine technologists rely on a single dosimeter to measure their work-related dose. Estimates of whole-body effective dose are based on the assumptions that the radiation is incident from the front and in a uniform beam. We sought to investigate these assumptions and also to quantify doses associated with different activities.

A single technologist wore 3 electronic dosimeters for 3 mo, at the front waist, the back waist, and the front collar. The technologist also recorded her activities throughout the day.

We found that the assumption of an anterior beam held about two thirds of the time, breaking down only when the technologist was receiving lower doses. Overall, the average whole-body dose was estimated correctly by assuming an anterior beam. We also found that irradiation was uniform (i.e., waist and collar badges gave equivalent readings) except when the technologist was performing injections. Then, the collar readings were 1.7 times the waist readings. Finally, average doses were measured for different types of activities. Performing injections registered a dose rate of approximately 2 microSv/h. Doses received while scanning ranged from 0.2 to 2 microSv/h. The average dose for a scan depended not only on the administered activity and isotope but also on the amount of patient contact required. Even for high activities, such as patients who had already received therapy, the dose to the technologist was low for patients requiring little assistance.

The assumption of anterior irradiation correctly estimates whole-body effective dose. The assumption of a uniform beam is good except when injections are being performed, when the upper torso receives a much higher dose than the waist. Overall, doses to the technologist were found to be 5.4 microSv/d for scanning and 12 microSv/d for injections. These correspond to 1.4 mSv/y and 3.2 mSv/y, respectively, which are comparable to naturally occurring radiation levels and are much lower than regulatory limits. However, if the dose to a particular technologist needs to be minimized (e.g., for a pregnant worker), the most effective strategy is for the technologist to be assigned patients requiring little contact or assistance and, in particular, to avoid administering injections.