ABSTRACT
Purpose: High Dose Rate (HDR) remote afterloading brachytherapy machine and advanced treatment planning system have made it possible to make variations in individual dwell times across a catheter according to tumour density and for sparing normal structures. New inverse planning technique such as Inverse Planning Simulated Annealing (IPSA) has also been introduced. But very few institutions are venturing towards volume based IPSA optimised intracavitary brachytherapy. This study focuses on dwell time deviation constraint (DTDC) feature of IPSA based optimization which restricts the large variation of dwell time across the catheter. Methods and Material: For this retrospective study we have generated IPSA optimised intracavitary brachytherapy plans for 20 cancer cervix applications. The initial DTDC value of each IPSA plan was kept 0.0. Later on gradual increment was made in DTDC values in step of 0.2. Plan modulation index (M) defined by Ryan L. Smith et al was used for characterising the variation of dwell time modulation with respect to gradual increase in DTDC parameter. Results: Plan modulation index gradually decreases with increasing value of DTDC from 0.0 to 1.0. There was the 83% decrease in M value from IPSA of DTDC 0.0 to fully constrained IPSA of DTDC1.0. There is reduction of 8.26% and 6.95% for D2cc values of rectum and bladder respectively for DTDC 1.0 compared to DTDC 0.0. Conclusions: One of the benefits of applying DTDC constrained in IPSA plan is that, it removes local hot spots. It's another advantage is the reduction in rectum and bladder dose.
ABSTRACT
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.
ABSTRACT
Objective To investigate the dosimetric difference between inverse planning simulated annealing(IPSA)and manual optimized plan for isodose line in interstitial brachytherapy for locally advanced cervical cancer and to provide a better optimization method for clinical application. Methods A total of 104 patients with cervical cancer were enrolled in this study. They received pelvic external beam radiotherapy and interstitial brachytherapy in five fractions. Both IPSA and manual optimized plan for isodose line were used to optimize the dose in each fraction. Dose volume parameters of the two plans were compared to analyze the dosimetric outcome by paired t-test. Results There were no significant differences in mean D 90and D 100for high-risk clinical target volume(HR-CTV)and D 90for intermediate-risk clinical target volume(IR-CTV)between the two groups(P>0.05). The IPSA group had a significantly higher D 100for IR-CTV than the manual optimized group(58.36±2.06 Gy vs. 53.99±2.17 Gy, P=0.025). For organs at risk,the IPSA group had a significantly lower mean rectum D 2ccand a significantly higher bladder D 2ccthan the manual optimized group(68.53± 2.85 Gy vs. 71.77± 1.79 Gy, P=0.002;80.49± 3.36 Gy vs. 78.71± 2.64 Gy,P=0.034). There was no significant difference in sigmoid D 2ccbetween the two groups(P>0.05). The IPSA group had significantly higher relative dose homogeneity index(HI)and conformity index (CI)of radiation dose for target volume than the manual optimized group(P<0.05), and there was no significant difference in overdose volume index(OI)between the two groups(P= 0. 1 0 7).Conclusions Compared with manual optimized plan for isodose line, IPSA can improve the dose distribution of tumor tissue,reduce mean rectum D 2cc,and increase CI and HI,so it is a preferable optimized treatment planning method in clinical application.
ABSTRACT
Objective To evaluate the clinical value of the afterloading brachytherapy inverse intensity-modulated radiotherapy of gynecological tumor.Methods Twenty patients with cervical cancer,were randomly divided into A and B groups,10 cases for each group.Group A received the afterloading brachytherapy inverse intensity-modulated radiotherapy.Group B received the three-dimensional comformal afterloading brachytherapy.The target volume dose distribution,organs at risk (rectum,bladder),shortterm curative effect and radioactive complications were analyzed on both groups.Results The dose homogeneity index of the target volume of group A was 52.43-± 0.45,better than that of group B (46.37 ± 1.45) (t =0.92,P ＜ 0.05).The maximum dose of rectum and bladder of group A were about 37％,35％,less than that of group B (t =1.34,1.39,P ＜ 0.05).The 75％ prescription dose irradiated volume of rectum and bladder of group A were about only 1/2 of group B (t =1.23,1.13,P ＜ 0.05).The local control rate of 96％ for group A was better than 93％ for group B (t =1.25,P ＜ 0.05).Conclusions Afterloading brachytherapy inverse intensity-modulated radiotherapy technique could be better than the three-dimensional comformal afterloading brachytherapy.It should be recommended for gynecological tumor.