Assessment of the extremity exposure during preparation and administration of 177Lu – results of a multi-center study

INTRODUCTION: 
Despite the increased use of 177Lu in nuclear medicine (NM) over the last 10 years, the knowledge of the actual exposure of the extremities due to manipulation of this pharmaceutical is limited. The purpose of this study is to assess the extremity dose during the preparation and administration of 177Lu-labelled radiopharmaceuticals in a wide range of NM practices. 

Method: 
Workers in 10 NM centers throughout Europe wore a ring dosimeter on the base of the index finger of the non-dominant hand during preparation and/or administration of 177Lu-labelled radiopharmaceuticals. Information on manipulated activity, tasks performed and protection measures was collected to allow sub-analyses. 

Results and discussion: 
The median ring dose per monitoring interval was 0.16 mSv, with a maximum of 2.27 mSv in one month. The median normalised dose amounted 3.5 µSv/GBq (range 0.5 to 525). The highest monthly doses were found for workers involved in preparation of the pharmaceutical. The workers performing manual administrations (6.5 µSv/GBq) showed higher normalised ring doses than those using the gravity method (3.5 µSv/GBq) or a syringe pump (1.0 µSv/GBq). Explanations for the wide range of normalised ring doses may be found in the different techniques applied in this study and the differences in minimum reportable doses of the dosimeters. When the data is extrapolated using a fingertip to ring dose ratio of 5, an annual fingertip dose of 1 to 136 mSv is found, with a median fingertip dose of 10 mSv per year. 

Conclusion: 
Extremity exposure during 177Lu handling remained well below dose limits. The highest normalized doses occurred during preparation and manual administration. Overall, this investigation shows doses remain low when appropriate radiation protection measures (e.g., shielding and minimizing time at short distance) are being applied.