Abstract: Objective To explore the use of Swedish medical company CMS 4.6.4 radiotherapy XIO system for the design process of cervical cancer postoperative IMRT plans in different iterative times of the same case,and to observe the Segment Weight Optimization(SWO)effect generated after the plan results.Methods Ten cases of cervical cancer patients were chosen,the use of XIO 4.6.4 CMS treatment system was performed for the development of the intensity modulated radiation therapy.In the SWO process,iterative times were used to generate different plans,without affecting the clinical dose target area requirements,and compared the organs at risk(OAR)by determining whether there were differences between dose and the number of segments,monitor units(MU).Results For the same patients,different iterative times within a certain range of SWO IMRT plan were selected to compare the different iterative times plan,femoral head,rectum and the bladder dose did not change the basic plan.The total number of segments and MU did not change significantly(P＞0.05).Conclusion IMRT plans in the use of CMS XIO 4.6.4 design of cervical cancer after operation in the process of using the iterative times below 100 times for SWO is the most suitable method for ensuring the organ dosimetry in radiotherapy.The total number of segments and the MU reduces the radiotherapy plan time so as to improve work efficiency.

Key words: Iterative times, Segment weight optimization(SWO), CMS XIO, Postoperative cervical cancer, Intensity modulated radiation therapy(IMRT)plan