| Background:Cervical cancer and endometrial cancer are both common gynecologic malignancies.Operative is the first choice for the early stage patients of cervical cancer and endometrial cancer,but vaginal stump is the main recurrent site.Vaginal intracavity brachtheray or combined external beam for the postoperative couble be used to reduce the recurrence of the vagina,while the influence of the surrounding organs is fairly small.Postoperative cervical cancer,postoperative endometrial carcinoma,vaginal cancer,vagina involvement of malignant tumors,and recurrence of the vagina are all its indications.It can be not only used as a supplement to external irradiation,but also an independent treatment choice.Vaginal applicator is a tool for brachytherapy,single channel cylinder is the most common applicator,and multi-channel cylinder has been used in recent years.However,due to the difference of surgical suture,drainage tube indwelling,and the patient individual difference of wound healed,the shapes of the vaginal stump are not consistent.The standardized cylinder can not avoid the large air gap between the applicator surface and the vaginal mucosa,no matter how many channels,the dose distribution and even effect can not be good though 3D brachtherapy plan.Individual applicator produced by 3D printing technology,whose dwell positions and times upfront calculated by 3D planning system is an ideal way to fitness and achieve the optimal dose distribution,but only case reports at home and abroad.The purpose of this research is to evaluate the value of 3D printing applicators in group,and improve the practical application flow,especially the definition and declineation of target area,which will provide a basis for further research and application of new vaginal applicator.Materials and methods:This study was divided into two parts.The first part was to explore the flow of production and application for 3D printing applicator,and to evaluate the value of 3D printing applicators in group.The second part was to futher explore the definition and delineation of target area,which was a difficulty in the flow.The detailed materials and methods were as followed:49 patients with postoperative endometrial carcinoma,cervical cancer and vaginal stump recurrence were enrolled in from Mar 2016 to Jun 2017 in our hospital.All patients were located by CT with vagina inserted 7 channels cylinders and packed contrast agent gauzes individually.Part 1:Dosimetric research of 3D printing vaginal applicator and cylinderCTV1(the direct external expansion of the applicator/vagina gauze),CTV2(adding the air gap before external expansion),CTV3(volume of the CTV2 top 1cm minus the volume of the applicator/gauze and the air gap at the top)and OARs were delineated.3D brachytherapy single-channel plans and six-channel plans were designed for center single channel and surrounding six channels of cylinder dwelled.Simulated 3D printing plans were designed for pre-set dwell positions on vagina packed gauze images and real 3D printing applicators.For dosimetric comparison,we normalized prescription dose per fraction to 500cGy and optimized each plan to reach D90CTV =500cGy.The air gaps were measured and analyzed.The length of upper-middle vagina was measured,and the morphology of vagina was analyzed by cluster analysis.Part 2:Target delineation reaseach on CT imaged 3D brachytherapy by 3D printing applicatorCTV2,CTV3,CTV2'(the volume of the CTV2 tip 1cm modified by actual CT image),CTV3'(CTV2 'top 1cm minus the volume of the source/gauze and the air gap at the top)were delineated and their plans were designed,and CTV2'(the volume of the CTV2 tip 1cm modified by actual CT image),CTV3'(CTV2 'top 1cm minus the volume of the source/gauze and the air gap at the top)and OARs were delineated.3D brachytherapy single-channel plans and six-channel plans were designed for center single channel and surrounding six channels of cylinder dwelled.Simulated 3D printing plans were designed for pre-set dwell positions on vagina packed gauze images and real 3D printing applicators.We normalized prescription dose per fraction to 500cGy and optimized each plan to reach D90CTV =500cGy.Compared the volume of target by different delineating mode(VCTV2 vs VVTV2),compared target coverage indexes when CTV2 was defined as target,compared the dosimetric difference among single-channel,six-channel,3D printing applicator groups when CTV2,were defined as target.Results:Part 1:Dosimetric relsearch of 3D printing vaginal applicator and cylinder1.Air gaps were found in 51.02%images by cylinder,volume 0.17cc(0.01,0.79),the largest volume air gap occurred in vaginal stump recurrence cases(0.35(0.25,0.79)cc),and the smallest occurred in postoperative cervical cancer.2.Air gaps cause target coverage occurred in 42.86%single-channel and 46.94%six-channel cylinder groups.D90 decreased by 3%(1%,14%)and 4%(1%,19%),V100 decreased by 3%(1%,10%)and 3%(1%,12%)in single-channel and six-channel groups(p=0.000).3.Target coverage decreased due to air gap in postoperative endometrial cancer,postoperative cervical cancer,recurrence of vaginal stump were 85.71%(12/14),75%(6/8),100%(3/3).4.V100 of CTV were significantly higher for 3D printing group compared to single-channel group and multi-channel group(90.01%(90.00%,90.18%)vs90.01%(90.00%,90.11%),p=0.003,90.01%(90.00%,90.18%)vs90.01%(90.00%,90.14%),p=0.004),V100 of CTV-1cm were more significant(D90:p=0.054,p=0.000;V100:p=0.000).5.DHI,DNR,OI were significantly lower for 3D printing group compared to other two groups(p=0.000).6.Mean dose of vagina mucosa in CTV were significantly lower for 3D printing group compared to other groups,the median decrease of 170cGy,133cGy,the maximum decrease of 435cGy,559cGy,p=0.000.D2cc of bladder and rectum for 3D printing group was between the other 2 groups,single-channel group was highest.7.The lengthes of upper-middle vagina in 3D printing applicator group were longer than cylinder group(5.31 ± 1.23cm vs4.95 ± 0.99cm,p=0.004).5 types of vagina shape were found in 49 patients,conical column(48.86%),flat column(26.53%),dog-ear column(12.24%),flat cone column(10.2%),and wide below narrow column(8.16%).Factor analysis found air gap was the most important factor led to target coverage decrease.The type of air gap often found form high to low were dog-ear column,flat column,vaginal stump recurrence,flat cone column.Part 2:Target delineation reaseach on CT imaged 3D brachytherapy by 3D printing applicator1.Target volume decreased 0.53cc(-1.96,8.08cc)used by direct expansion compared with CT modified in cylinder group,lead to D90 decrease 3.37%?4.00%,V100 decrease 2.21%-3.80%,p=0.000.No difference was in 3D printing group.2.V100 in 3D printing group were significantly higher than single-channel,six-channel cylinder groups,especially in top lcm,at the same time,six-channel was higher than single-channel,when CT modified mode(p=0.000).DNR,01 in 3D printing group were lowest.Mean dose of vagina mucosa in CTV were significantly lower for 3D printing group compared to other groups,the median decrease of 239.18cGy,160.18cGy,the maximum decrease of 779.32cGy,761.32cGy,p=0.000.D2cc of bladder and small intestine in 3D printing group were lowest,D2cc of sigmoid were highest,D2cc of rectum were between the other 2 groups.No overdose occurred in every group.Conclusion:Compared to cylinder,3D printing applicator reduced air gap and vaginal fold in tops,increased target coverage,avoid high-dose hot spots and low-dose cold spots,especially in special target area,such as Dog-ear column,flat column,flat cone column,and vaginal stump recurrence had more obvious advantage.Samples increased would contribute to the research and development of new source applicators.Combined with 3D brachytherapy plan by MRI/CT image modified,which was expected to further reduce prescription dose and toxicity. |
PDF Full Text Request