β-radiation exposure with 188Re-labelled pharmaceuticals

Abstract

SummaryAim: The number of therapies with radiopharmaceuticals labelled with 188Re is increasing requiring the documentation of the beta radiation exposure Hp(0.07) of the staff at all working and production sites and during the application and follow-up of the patient according to the new German Radiation Protection Law (StrlSchV). However, data for β-radiation exposure are rare. Therefore, we determined the personal dose Hp(0.07) of the skin of the hands handling 188Re radiopharmaceuticals to identify steps of high radiation exposure and to optimize working conditions. Method: Thermoluminescence dosimeters (TLD 100) were fixed to the fingertips of the radiochemist, the physician and the nurse and compared to official ring dosimeters. In addition, to monitor radiation exposure continuously readable electronic beta- and gamma dosimeters EPD (Siemens) were used. At eight days in which therapies were performed these readings were evaluated. Results: Considering one therapy with a 188Re-labelled radiopharmaceutical the middle finger of the radiochemist (production) and the physician (application) showed a radiation burden of 894 and 664 μSv/GBq, respectively. The cumulative dose of the fingertips after eight days of therapy was 249 and 110 mSv for the radiochemist and physician, respectively. A cumulative finger dose after eight days of therapy of 17 and 38 μSv/GBq was found for physician and nurse leading to a Hp(0.07) of 3 and 6 mSv, respectively. Preparing the radiopharmaceutical labelled with 20GBq of 188Re the reading of the personal electronic dosimeter of the radiochemist showed a γ-dose rate H . p(10) of 55 μSv/h and a β-dose rate H . p(0.07) of 663 μSv/h which are obviously not representative for the true radiation dose to the skin of the fingertips. Conclusion: During therapy with 188Re-labelled radiopharmaceuticals the true radiation dose to the skin of the finger tips exceeds by far the readings of the official ring dosimeters as well as the continuously readable beta- and gamma dosimeters. This means a risk in exceeding the radiation limit of 500 mSv/a given in the German Radiation Protection Law (§55 StrSchV) primarily in the working field of the radiochemist and the administering physician.