VMAT计划中计算网格尺寸对宫颈癌放疗剂量的影响

Effect of Calculation Grid Size on Radiotherapy Dose of Cervical Cancer in VMAT Planning

目的探究在Monaco计划系统中使用容积弧形调强放射治疗(Volumetric Modulated Arc Therapy,VMAT)计划时计算网格尺寸对于宫颈癌病例优化的影响。方法选择在我院Monaco系统进行宫颈癌放疗的15例患者的CT图像,计划采用Monaco计划系统中VMAT旋转治疗方式,通过仅改变计划设计参数中计算网格尺寸(2、3、4、5、6、7、8 mm),得到计划的结果,并对此进行靶区和危及器官的受量分析。结果以计算网格尺寸2 mm为参考,计划靶区剂量的D_(98)、D_(mean)、D_(2)和均匀指数(Homogeneity Index,HI)在计算网格尺寸为3 mm时出现明显差异(P<0.05),随着计算网格尺寸增大,D_(mean)、D_(2)和HI仍差异显著(P<0.05)。当计算网格尺寸为5 mm时,小肠的V_(40)和结肠的V_(30)、V_(40)出现显著性差异(P<0.05);计算网格尺寸为4 mm时,膀胱的V_(45)出现显著差异(P<0.05);计算网格尺寸为8 mm时,左股骨头出现显著性差异(P<0.05)。结论在Monaco计划系统中,对于宫颈癌患者计算网格尺寸为3 mm时是合适的选择,可为临床计划的设计提供一定的参考。在满足治疗效果的同时可提高治疗的效率。

Objective To explore the effect of calculating grid size on cervical cancer case optimization when using volumetric modulated arc therapy(VMAT)plan in Monaco planning system.Methods CT images of 15 cervical patients who received radiotherapy in our hospital in Monaco system were selected,and the plan was optimized using the rotational treatment method of VMAT in Monaco planning system.The planned results were obtained by only changing the grid size(2,3,4,5,6,7,8 mm)in the planning design parameters.The target area and organs at risk were analyzed.Results Using 2 mm calculation grid size as reference,the D_(98),D_(mean)、D_(2) and homogeneity index(HI)of PTV were statistically significant differences when the calculation grid was 3 mm(P<0.05).As the calculation grid increased,the difference of D_(mean)、D_(2) and HI were still statistically significant(P<0.05).When the calculation grid increased to 5 mm,for organs at risk,there was significant difference between the V_(40) of the small intestine and the V_(30) and V_(40) of the colon(P<0.05).When the calculation grid was 4 mm,the V_(45) of the bladder had significant difference(P<0.05).When the calculation grid was 8 mm,the left femoral head was significantly difference(P<0.05).Conclusion In Monaco planning system,the mesh size of 3 mm is an appropriate choice for cervical cancer patients,which can provide a certain reference for the design of clinical planning.This will not only improve the efficiency of treatment,but also satisfy the therapeutic effect.