The effect of different particle activities and tumor shrinkage speed on the dosimetric parameters of the target area after 125I particle implantation
10.3969/j.issn.1008-794X.2025.03.008
- VernacularTitle:125I粒子植入后不同粒子活度和肿瘤缩小速度对靶区剂量学参数的影响
- Author:
Huimin YU
1
;
Jinxin ZHAO
;
Jiantao DONG
;
Xuemin DI
;
Zhen GAO
;
Juan WANG
;
Hongtao ZHANG
Author Information
1. 050051 河北石家庄 河北省人民医院肿瘤一科
- Keywords:
125I particle;
dynamic dose;
target volume;
shrinkage rate;
activity
- From:
Journal of Interventional Radiology
2025;34(3):272-277
- CountryChina
- Language:Chinese
-
Abstract:
Objective To discuss the effect of different particle activities and tumor shrinkage speed on the dosimetric parameters of the target area at the same prescription dose after 125I particle implantation.Methods A 6cm-sized cube tumor model was outlined by using a computerized three-dimensional treatment planning system(3D-TPS)with a prescription dose(PD)of 100 Gy,and 125I particle activities of 0.4 mCi and 0.8 mCi were selected.Assuming that the tumor shrinks centripetally after seed implantation and that the 125I particles were uniformly and centripetally concentrated without shedding or wandering,the tumor volume shrank at different rates every month after implantation(0,5％,10％,15％,20％,25％,30％,35％,40％,45％and 50％),according to the different activities of 125I particles,the experiments were divided into A1-K1 group(0.4 mCi)and A2-K2 group(0.8 mCi).Based on the 125I particle decay law,the validation program(using TPS simulation of the A1-K1 group and A2-K2 group at postoperative 1,2,3,4,5 and 6 months)obtained the dose received by 90％of the target volume(D90)in the two groups with different 125I particle activities at different postoperative time points,the percentages of the target volume covered by the 100％,150％and 90％prescription dose(V100,V150,V90),and the mean dose(Dmean).By comparing the differences in D90,V100,V150,V90 and Dmean after tumor implantation of 125I particles with different activities,the dosimetric impact of the tumor target area shrinking at a rate of 0～50％after implantation of 125I particles with different activities into tumor tissues was analyzed.Results When the monthly shrinkage rate of the tumor target area was≤30％,there was no obvious difference in D90 between the 0.4 mCi group and 0.8 mCi group in 1～6 months after surgery.When the monthly shrinkage rate of the tumor target area was＞30％,the D90 of 0.8 mCi group was higher than that of 0.4 mCi group;when the monthly shrinkage rate of the tumor target area was＜25％,the V90 of 0.4 mCi group was higher than that of 0.8 mCi group,and the changes of V90 of the two groups tended to be the same in the 5th～6th month after surgery.When the monthly shrinkage rate of the tumor target area was ≥30％,the V90 of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more significant,the results of V100 were consistent with those of V90.When the monthly shrinkage rate of tumor target area＜35％,V150 of 0.4 mCi group was higher than that of 0.8 mCi group,when the monthly shrinkage rate of tumor target area ≥35％,V150 of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more prominent.When the monthly shrinkage rate of tumor target area＜25％,Dmean of 0.4 mCi group was higher than that of 0.8 mCi group,when the monthly shrinkage rate of tumor target area ≥25％,Dmean of 0.8 mCi group was higher than that of 0.4 mCi group,and with the increasing of shrinkage rate,the difference between the two groups become more and more obvious.Conclusion With the same prescription dose,when the tumor target area shrinks at a rate of＜30％per month,the activity of 125I particles has little effect on D90,and all V90,V100,V150 and Dmean in the low activity group are higher than those in the high activity group,meanwhile the homogeneity of the target area is relatively good;when the monthly shrinkage rate of tumor target area ≥35％,all D90,V90,V100,V150 and Dmean in the high activity group are higher than those in the low activity group,and the duration of the presence of high-dose area is long.This difference becomes more obvious with the increasing of the monthly shrinkage rate of the target area.
