Comparison Of Novel Radiotherapy Techniques In The Application Of Pelvic Radiotherapy After Cervical Cancer Surgery

Objective:In this study we compared the clinical application of Tomotherapy,Halcyon the novel O-ring accelerator and Trilogy the traditional accelerator in postoperative radiotherapy for cervical cancer,including dosimetric evaluation,treatment efficiency and plan QA,in order to explore the clinical features of the new technique in postoperative radiotherapy for cervical cancer,and to provide more basis for clinical selection.Methods:We retrospectively selected 20 cases of cervical cancer patients treated by postoperative radiotherapy.Based on the scanned CT images,we defined the same contour protocol for the target and organ at risks.Under the same prescription dose protocol and organ dose limitation,we used treatment planning system to create the Trilogy based double arcs VMAT treatment plan group,the Hi Art Tomotherapy based tomotherapy treatment plan group,and Halcyon based four arcs VMAT treatment plan group,in silico planning study.The dosimetric parameters of the target area and normal tissues of these three groups were compared.We evaluated the quality of dose distribution,total MU value,beam released time and Gamma pass rate of the patient plan QA.Results:All three plan groups could meet the dosimetric requirements of clinical treatment.The TOMO group had slightly better Homogeneity index of PTV than Trilogy and Halcyon groups,but there's no statistically significant difference.TOMO group had bigger variance of DVH distribution of PTV than the other two groups,showing a weak plan consistency.The bladder statistic showed a higher average dose and a lower DVH value of the sub-high dose group in the TOMO group than in the Halcyon and Trilogy groups,but there was still no significant difference.The TOMO group had the lowest average rectal dose,but there was no statistically difference.The volume of the high-dose area of the Trilogy group was the smallest,while the volume of the high-dose area of the TOMO group was the largest.The mean values of intestinal DVH in these groups were very similar,and a whole-view results showed that the intestinal DVH of the Trilogy group was the best.The low dose area of the femoral head was the highest in the TOMO group,with Trilogy slightly superior to Halcyon.The average beam time of the TOMO group was significantly higher than that of the Trilogy and Halcyon groups,with MU value 7.6 times higher than that of the Halcyon group.The plan QA gamma rate of all three groups met the clinical requirements,and the Halcyon QA gamma rate was the highest.Conclusion:The quality of the VMAT treatment plan based on Halcyon 1.0 O-ring accelerator is comparable to that of traditional accelerator based VMAT plan and tomotherapy plan,both of which can meet the clinical treatment needs.However,the treatment time of Halcyon accelerator is shorter,and the treatment precision is higher.A Further study is needed to compare the efficacy of clinical treatment.