基于蒙特卡洛算法下宫颈癌放疗计划退行性迭代的研究OA

Objective To investigate the triggering factors of retrogressive dose iteration and the feasibility of the high-dose iteration position truncation calculation scheme of the Monaco treatment planning system(TPS)in radiotherapy for cervical cancer(referred to as"radiotherapy").Methods Thirty patients who underwent volumetric modulated arctherapy(VMAT)for cervical cancer from June 1,2023 to April 1,2024 were selected as the research subjects.The prescribed dose was 45 Gy/25 F,and two full-arc VMAT plans were designed for each patient.After the flux optimization was completed,the modulation degree(MD)was statistically analyzed through the Progress Meter,and the experimental cases were divided into the High MD group and the Low MD group based on the difference rate.The difference rate between the results of flux optimization and dose optimization of planning target volume(PTV)V45(the percentage of organs receiving at least 45 Gy dose,and other similar)in the two groups was analyzed;The patients in the High MD group(Plan HLC)were further studied to analyze the differences in the V45 of PTV and the dosimetry of major organs at risk(OARS),plan characteristic parameters,plan dose distribution and plan verification results between the high MD plan group and the conventional automatic completion plan group.Results The MD values of the 30 enrolled cases were statistically analyzed.There were 19 cases in the High MD group(MD>3),accounting for 63.3%,and 11 cases in the Low MD group(MD<3),accounting for 37.7%.The difference rate between the V45 flux optimization result and the dose optimization result of PTV in the High MD group was significantly higher than that in the Low MD group.During the entire dose iteration process of the High MD group,a significant drop was observed after the V45 of PTV reached its peak.In the further analysis of the experimental cases of Plan A and Plan HLC,the dose differences in the target area and the main OARs were statistically significant[V45 of PTV:t=3.116,P=0.013;Small intestine D0.03cc(the maximum dose value of 0.03 cm3 by volume):t=1.241,P=0.022;Rectal V40:t=6.183,P=0.021;Bladder V40:t=3.174,P=0.032].The analysis of the dose cloud graph and the dose-volume histogram showed that the difference trends of the two groups were similar.The statistical results of the characteristic parameters of dose optimization indicated that the differences in each result between the two groups were statistically significant(dose optimization time of X-ray Monte Carlo algorithm:t=1.607,P=0.001;Planned photon utilization rate:t=4.962,P=0.023;Number of subfields:t=2.512,P=0.022;Machine hop count:t=8.201,P=0.001).The verification results of both groups of plans met the clinical requirements,but the Plan A group was slightly higher than the Plan HLC group.Conclusion When using Monaco5.11 TPS to optimize the radiotherapy plan for cervical cancer,the MD value is the main factor triggering retrogressive iterations.The high-dose iterative position cut-offPlan when degenerative iterations occur meets the clinical implementation conditions,and the obtained Plan HLC plan can be used for radiotherapy.