Radiation dose rates of differentiated thyroid cancer patients after 131I therapy

Postoperative I-131 treatment for differentiated thyroid cancer (DTC) can create a radiation hazard for nearby persons. The present prospective study aimed to investigate radiation dose rates in I-131-treated DTC patients to provide references for radiation protection. A total of 141 I-131-treated DTC patients were enrolled, and grouped into a singular treatment (ST) group and a repeated treatment (RT) group. The radiation dose rate of I-131-treated patients was measured. The rate of achieving discharge compliance and restricted contact time were analyzed based on Chinese regulations. Multivariate logistic regression analysis was used to analyze the independent factors associated with the clearance of radioiodine. The rate of achieving discharge compliance (I-131 retention < 400 MBq) was 79.8 and 93.7% at day 2 (D2) for the ST and RT groups, respectively, and reached 100% at D7 and D4, respectively. The restricted contact time with I-131-treated patients at 0.5 m for medical staff, caregivers, family members, and the general public ranged from 4 to 7 days. Multivariate logistic regression analysis showed that the 24-h iodine uptake rate was the only significant factor associated with radioiodine clearance. For the radiation safety of I-131-treated DTC patients, the present results can provide radiometric data for radiation protection.