Objective To investigate the surrounding and central dosimetric distribution difference of the same activity, same number of 125I seeds. Methods 3D treatment planning system (3D-TPS) was used to separately sketch out 7 cubes with side length of 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm and 5 cm;simulations of different tumor sizes were established, into which 125I seeds with activity of 0.5 mCi were respectively loaded. All seeds were distributed at the periphery of the tumor (peripheral group) with the prescribed dose of 145 Gy. The dose volume histogram (DVH) was printed and the 90% of target volume absorbed dose (D90), 90% of prescription dose coverage target volume percentage (V90), the maximum dose and mean dose were determined. Then the seeds in every cube were distributed into the center (central group) and the above parameters were calculated by using the same method. Results The mean D90 of the peripheral and central group was (147.29 ±0.58) Gy and (106.08 ±9.40) Gy respectively, the difference between the two groups was statistically significant (t=-4.292, P=0.005). The mean V90 of the peripheral and central group was (95.46±0.44)% and (79.07±4.19)% respectively, the difference between the two groups was statistically significant (t=-3.831, P=0.009). The mean maximum dose of the peripheral and central group was (1 224.65 ±12.7) Gy and (1 532.48 ±48.54) Gy respectively, the difference between the two groups was statistically significant (t=6.823, P=0.000). The mean value of average dose of the peripheral and central group was (192.14 ±2.89) Gy and (179.81 ±5.40) Gy respectively, the difference between the two groups was statistically significant (t=-2.847, P=0.029). Conclusion The dose distribution is directly influenced by the distribution pattern of the 125I seeds. When the number and activity of the 125I seeds are the same, the peripheral seeds implantation has a better dose distribution.

Objective To investigate the optimal measures and clinical effect of perioperative nursing care for patients with cephalocervical cancer treated with CT-guided radioactive 125I seed implantation. Methods Preoperative, intraoperative and postoperative continuous and comprehensive nursing was strictly carried out in 93 patients with cephalocervical cancer who underwent CT-guided radioactive 125I seed implantation treatment. The clinical results were analyzed and evaluated. Results The 125I seed implantation procedure was successfully accomplished in all 93 patients; the success rate was 100%. Shedding of 6 particles was observed in one patient, and shedding of 5 particles was observed in another patient; grade Ⅳskin injury was seen in 3 cases, which were improved after symptomatic treatment. All patients were uneventful at the time of discharge from hospital. Conclusion To ensure a successful CT-guided radioactive 125I seed implantation for the treatment of cephalocervical cancer, professional, meticulous and standardized nursing is the important guarantee.

Objective To explore the dosimetric effects of the same number and activity of radioactive 125I seeds in different plane arrangements. Methods Simulated 9 distribution modes using 9 125I seeds were designed by three- dimensional treatment planning system (3D- TPS), and the isodose curves of 60 Gy, 80Gy, 130 Gy, 145 Gy and 200 Gy were obtained. The areas enclosed by the isodose curves, the longer and shorter radius of these isodose curves and the medical cost per unit area were calculated with the professional image analysis software. Results Obvious differences in areas enclosed by the isodose curves, the longer and shorter radius of these isodose curves and the medical cost per unit area existed between each other among the nine different distribution modes of 9 125I seeds. The distribution modes that had the maximum areas enclosed by 60 Gy, 80 Gy, 130 Gy, 145 Gy and 200 Gy isodose curves were x1.5y1.5, x1y1.5, x1y1, x1y1 and x0.5y1, respectively, with the corresponding areas of 1 583.86 mm2, 1 146.03 mm2, 768.30 mm2, 621.85 mm2 and 480.97 mm2, respectively. Conclusion The peripheral dose and the therapeutic efficacy are significantly influenced by the arrangement of 125I seeds when the same number and activity of the seeds are used. The dose distributions are more homogeneous when the maximum areas enclosed by the isodose curves are obtained.

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.