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.%目的：探讨同活度、同数量125I粒子周边分布与中心分布的剂量学差异。方法采用计算机三维放射治疗计划系统（3D-TPS）勾画出2、2.5、3、3.5、4、4.5、5 cm等7种边长的正方体，模拟不同大小肿瘤，分别载入0.5 mCi 125I粒子，处方剂量145 Gy，粒子周边分布（周边组），得出剂量体积直方图（DVH）及90%靶体积吸收剂量（D90）、90%处方剂量覆盖的体积占靶体积百分比（V90）、最高剂量点、平均剂量等参数；同样方法将以上各肿瘤中载入粒子作中心分布（中心组），得出上述参数。结果周边组和中心组D90均数分别为（147.29±0.58）Gy和（106.08±9.40）Gy，差异有统计学意义（t=-4.292，P=0.005）；V90均数分别为（95.46±0.44）%和（9.07±4.19）%，差异有统计学意义（t=-3.831，P=0.009）；最高剂量均数分别为（1224.65±12.7）Gy和（1532.48±48.54）Gy，差异有统计学意义（t=6.823，P=0.000）；平均剂量均数分别为（192.14±2.89）Gy和（179.81±5.40）Gy，差异有统计学意义（t=-2.847，P=0.029）。结论125I粒子不同分布模式直接影响剂量分布，粒子数目和活度相同时周边布源有较好的剂量分布。
展开▼
