Radiation exposure rate from 131I-treated hyperthyroid patients -: A dynamic study, with data for up to 42 D post therapy

Hyperthyroid patients treated with radioactive I-131 are a potential source of external and internal exposure to family members and others in close contact with these patients. Information on the exposure rate from the patient on any day post administration of the dosage may be helpful when implementing an effective radiation safety or ALARA strategy for the family or members of the general public. Exposure rate measurements were completed on 78 out of 128 hyperthyroid patients participating in the study. Measurements were taken at 1 m, 0.6 m, and 0.3 m from the patient for eight different dose regimens and for up to 42 d post dose administration. The measured exposure rate was plotted against days post dose administration to demonstrate how quickly the exposure rate reduced with time. As anticipated, significant positive correlation was found between exposure rate at 1 m, 0.6 m, and 0.3 m for all radioactive dose regimens. No significant correlation was found between the external exposure rate reduction post-therapy and the I-131 uptake at 2 or 24 h, prior to therapy. This work is a dynamic study that provides comprehensive external radiation exposure rate measurements in hyperthyroid patients post therapy dose administration and may serve as a database for radiation safety related decision-making.