RESUMO
Objective To evaluate the effect of an inverse planning simulated annealing (IPSA) in the treatment of cervical cancer with combined intracavitary and interstitial three-dimensional brachytherapy.Methods A total of 60 patients with locally advanced cervical cancer who received both external beam radiotherapy and combined intracavitary and interstitial brachytherapy in our hospital from October 2016 to July 2018 were enrolled.Patients were divided into four groups with 15 patients each according to the number of needles applied (1,2,3,and 4 needles,respectively).Dosimetric distributions were optimized with both Graphical optimization (GRO) and IPSA.Paired t-test was applied to compare the dosimetric differences between plans optimized with GRO and IPSA.Results The Dg0 and V100 of IPSA plans were higher than those of GRO (t=-4.742,-4.823,P＜0.05),while the conformity index (CI) and conformal index (COIN) were slightly lower than those of GRO plans (t=9.642,8.783,P＜0.05).No significant difference in the V150,V200,V300 between IPSA and GRO (P＞0.05) was observed.There was also no significant difference in the D2cm3 of bladder and rectum between IPSA and GRO (P＞0.05).The difference of Dg0 between IPSA and GRO was increased as the number of implanted needles increased,which increased from 4 cGy to 14 cGy as the number of needle increased from 1 to 4.The difference of V100 between GRO and IPSA was also increased as the number of needle increased.Conclusions In the treatment of cervical cancer with combined intracavitary and interstitial threedimensional brachytherapy,IPSA plan could improve the target coverage(D90,V100)without increasing the dose to the OARs and high dose region in the target compared with GRO.With the numbers of needles increased,the advantage of IPSA increased in terms of target coverage.
RESUMO
Objective To compare the differences and characteristics of the dose distribution of the two optimization methods in the three dimensional brachytherapy,and provide the basis for clinieal treatment.Methods Excel 2007 was used to generate random number.And a total of 21 patients of cervical cancer were selected from those who have completed the treatment.Inverse simulated annealing optimization (IPSA) plans were designed for graphical optimization (GO) plans.The dose volume histogram (DVH) parameters of the targets (V100％,V150％) and the organs (D1 cm3,D2cm3) of the two methods were analyzed.Results The targets dose of both plans could meet the prescription requirements.There was no statistically significant difference in the dose parameters of all targets (P ＞ 0.05).The closes of D1 cm3 and D2cm3 in the bladder of IPSA plan were significantly lower than that of the GO plan (t =3.596,3.490,P ＜ 0.05).There was no statistically significant difference in the dose parameters of rectum (P ＞ 0.05).Conclusions For cervix brachytherapy,the GO and IPSA have no effect on targets dose,but IPSA optimization can reduce the maximum dose of bladder.