Radiation dose trends for nurses caring for radiation therapy inpatients

Objectives The radiation dose trend for nurses who cared for 422 inpatients administered more than 1110 mBq I-131and 470 brachytherapy inpatients is tracked from 1990 to 2007.

Methods Therapy patients were admitted to approved rooms only. Each nurse was assigned one radiation badge that they wore exclusively for one month. Pregnant nurses were excluded. Film badges were used until 1999, then AlO₂ badges were used to monitor dose equivalent which was reported in mrem. The brachytherapy inpatients included I-125, Cs-137, and Ir-192 temporary implants.

Results In 1990, the cumulative dose was 1410 mrem for 324 nurses; ave 4.4 mrem/nurse; max dose to any nurse was 120 mrem for 57 brachytherapy and 38 I-131 therapy inpatients. From 1990 through 2007, positive correlations were found between (1) no. of nurses and total no. of therapies (r = 0.87), (2) cumulative mrem and total no. of therapies (r = 0.69), and (3) cumulative mrem and no. of I-131 therapies (r = 0.64). Following the 1997 NRC rule change, the no. of inpatient I-131 therapies declined from 64% (50 of 78) to 1.6% (2 of 129) in 2007. High dose rate brachytherapy replaced most of the inpatient brachytherapy in 2000. In 2007, the cumulative dose declined significantly to 100 mrem for 92 nurses; ave 1.1 mrem/nurse; max dose to any nurse was 10 mrem for 2 I-131 and 3 brachytherapy inpatients.

Conclusions The highest ave dose per nurse and max dose to any one nurse were well below 1/10^th of the legal radiation dose limits. When properly trained, the expected radiation dose to nurses who care for I-131 thyroid cancer and brachytherapy inpatients is relatively low.