Personalized radioprotection in tumor patients after 125I seed brachytherapy

Abstract

Objective

To investigate patient-specific radioprotection methods for people in close contact with cancer patients treated by ¹²⁵I-seed implantation.

Methods

The initial dose rates (Ḋ₀) at distances of 30 and 100 ​cm from 80 patients who had undergone ¹²⁵I-seed implantation were measured within 24 ​h of the procedure. The dose rate at t (Ḋ_t) and effective dose (E) were calculated according to the measured values of Ḋ₀. The appropriate precaution times for general adult family members, spouses, coworkers, and children or pregnant women were determined, and the relationships between Ḋ₀ and precaution time for different close-contact groups were derived by curve-fitting the corresponding data.

Results

The mean Ḋ₀ values of 80 patients at distances of 30 and 100 ​cm were (15.24 ​± ​11.25) μSv/h and (1.96 ​± ​2.63) μSv/h, respectively (P ​< ​0.05). The mean values and range of precaution time for general adult family members, spouses, coworkers, and children or pregnant women were (4.17 ​± ​16.55), (102.93 ​± ​49.22), (51.00 ​± ​61.29), and (34.27 ​± ​56.90) d; (0–90.61), (0–234.01), (0–247.81), and (0–224.69) d, respectively. Furthermore, a logarithmic relationship between Ḋ₀ and precaution time (Y) was observed for the different groups. The equations of these relationships were determined to be Y ​= ​−131.569 ​+ ​83.256 lnḊ₀ for general adult family members, Y ​= ​−108.532 ​+ ​83.318 lnḊ₀ for spouses, Y ​= ​25.470 ​+ ​83.318 lnḊ₀ for coworkers, and Y ​= ​2.585 ​+ ​83.229 lnḊ₀ for children or pregnant women.

Conclusions

Some cancer patients treated by ¹²⁵I-seed brachytherapy emit over-dose levels of γ-rays, necessitating radiation protection for their close contacts. However, appropriate patient-specific radiation protection for different close contacts can be determined based on the precaution time calculated using the Ḋ₀ value.