Abstract:
Objective To explore the related factors affecting the reduction of radiation dose rate and to estimate the hospitalization days in papillary thyroid cancer (PTC) patients with postoperative after first 131I therapy.
Methods A total of 167 patients with PTC were hospitalized and treated with iodine-131 from May 2015 to November 2018 at Zhujiang Hospital, Southern Medical University. The patients were divided into the high-dose group (63 cases) and the low dose-group (104 cases). The radiation dose rates of the two groups of patients at different time points were measured at a distance of 1 m, the required hospitalization isolation time was analyzed, and the factors related to the reduction in radiation dose rate were analyzed by using multiple linear regression method. Two independent samples nonparametric test and t-test were used to compare the differences between groups.
Results After iodine-131 treatment for the first time, the radiation dose rate of the patients with PTC decreased exponentially with time, and the radiation dose rates of the high-dose group(70.62± 34.45), 15.64 μSv/h at 24 h and 48 h after iodine-131 treatment were significantly higher than those of the low-dose group (11.27±5.13), 2.03 μSv/h (t=−13.581, −7.952, both P < 0.01). Approximately 81.0% (51/63) and 90.5% (57/63) of the high-dose group were discharged after iodine-131 treatment for 48 h and 72 h, respectively. By contrast, 99% (103/104) of the low-dose group was discharged after iodine-131 treatment for 24 h. According to multiple linear regression analysis, the effects of iodine-131 dose, iodine uptake rate at 2 h on radiation dose rate at 24 h in the high dose group were statistically significant (F = 9.23, complex correlation coefficient R2 = 0.212, P < 0.01), and both iodine-131 dose and iodine uptake rate at 2 h had positive correlation with 24 h radiation dose rate. The effects of gender, iodine uptake rate at 24 h and residual thyroid volume (method 3) on radiation dose rate at 48 h in the high-dose group were statistically significant (F=34.45, complex correlation coefficient R2 = 0.622, P < 0.01), moreover the radiation dose rate at 48 h was positively correlated with iodine uptake rate at 24 h and residual thyroid volume, and negatively correlated with gender. The effects of iodine-131 dose and drinking water amount at 24 h on the radiation dose rate at 24 h in the low-dose group were statistically significant (F=12.76, complex correlation coefficient R2=0.186, P < 0.01), furthermore the radiation dose rate at 24 h in the low-dose group was positively correlated with iodine-131 dose, and negatively correlated with drinking water amount at 24 h.
Conclusions After the first iodine-131 treatment for 24 h, the main factors influencing the reduction in the radiation dose rate of patients with PTC were the dose of iodine-131. The main factors influencing the reduction in radiation dose rate after 48 h were the iodine uptake rate of the thyroid at 24 h, the volume of the residual thyroid gland, and the gender of the patient. The mean hospitalization time in low dose group and high dose group was about 1 day and 2 days respectively.