Objective To study the effective dose and precaution time of the irradiation of the close contact from the radiators who underwent implantation of radioactive 125Ⅰ seeds so as to guide scientifically people how to avoid radiation damage.Methods Twenty patients with different types of cancer underwent implantation of radioactive 125Ⅰ seeds with the median value of implantation depth of 2.16 cm.Within 24hs after the operations the dose rates 30 cm and 100 cm from the skin were measured with pocket-size radiometer so as to imitate the situations of the close contacts.The effective doses and precaution times of different persons were calculated according to relevant formula.Results The dose rate a person received at the same time points (1,54,78,and 109 d,respectively) decreased along with the increase of the distance from the skin (t =5.962,5.961,5.961,5.962,P ＜ 0.05).and the dose rate a person received at the same distance from the skin decreased along with the extension of time (30 cm:t =6.236,6.236,6.235,P＜0.05;100 cm:t=7.310,7.315,7.314,P＜0.05).At different time points,the dose rates at 30 cm distance point were all significant higher than those at the 100 cm point (P ＜0.05).The adult living together,minors and pregnant women sharing the room,colleagues,adults who slept together with the patients began to reach the 50％ dose constraint values 0,54,78 and 109 days after the operation.Conclusions After their precaution time,it's safe to contact with the patients for the groups;otherwise,it's necessary to take some protect works within the precaution time.

Objective:To study the radiation dose rate and effective dose in ambient environment due to 125I seed implantation in the treatment of the patients suffering abdominal and pelvic tumors, so as to provide reference for occupational protection of different groups. Methods:Within 24 hours after operation, the radiation dose rate to 42 patients with abdominal and pelvic tumor with 125I seed implantation was monitored by using pocket dosimeter. The relationships between the total activity in the implanted particles and the measured dose rate, as well as between the implanted depth and the dose rate under the standard activity, were obtained by curve fitting. According to the formula, the relationship between the dose rate and the warning time was calculated. Results:The dose rates at 30 cm, 50 cm and 100 cm of vertical particle implantation site were (6.92±2.87), (4.10±1.62) and (1.30±0.48) μSv/h, respectively ( χ2=73.71, P<0.05). The dose rates on the left and right sides were (0.378±0.156) and (0.384±0.153) μSv/h at 30 cm, (0.170±0.089) and (0.17±0.086) μSv/h at 50 cm, (0.039 ±0.014) and (0.043±0.017) μSv/h at 100 cm, respectively ( χ2=76.19, 76.33, P<0.05). There was a linear relationship between the dose rate at the vertical particle implantation site and the total activity in the implanted particles, and between the dose rate and the implantation depth under the standard activity. The relationship between the warning time and the dose rate to adults in the same bed, co-workers, minors in the same bed and pregnant women were as follows: t ( d)=-106.616+ 83.779ln D( t), t ( d)=26.556+ 85.933ln D ( t), t( d)=3.088+ 85.017ln D( t). Conclusions:After 125I seed implantation, the radiation dose in the ambient environment is low, ensuring the radiation safety; and the measured dose rate decreases with the decrease in the total activity in the implanted particle and the increase in the implantation depth; at the same time, the warning time for different groups is calculated according to the measured dose rate or the total activity in the implanted particle and the depth of the implanted particle, so as to carry out individualized protection.