不同扫描条件对射波刀剂量计算的影响

Effects of different scanning conditions on dose calculation of CyberKnife

目的:研究不同扫描条件对射波刀剂量计算的影响。方法:设置不同的管电压(80、100、120和140 kV)和管电流(150和300 mA),采用飞利浦大孔径CT模拟定位机获取Lucy头颈部模体的CT图像,利用射波刀Multiplan■治疗计划系统对扫描得到的CT图像进行放疗计划设计,分析不同扫描条件对感兴趣区的CT值、感兴趣区和靶区及靶区外壳层的剂量值的影响。采用SPSS 22.0软件进行统计学分析。结果:管电流固定时,管电压对CT值的影响有统计学意义(P<0.05),且感兴趣区的CT值与管电压呈负相关。不同CT扫描条件对剂量分布有不同程度影响,管电流越高,剂量分布越紧凑,剂量跌落越陡峭,但无统计学意义;不同管电压对靶区和正常组织右眼50%体积剂量D50的影响具有统计学意义(P<0.05),说明管电压可以改变靶区和正常组织的剂量分布。结论:不同扫描条件直接影响CT值的大小,且对放疗计划的剂量计算以及剂量分布具有一定程度的影响。因此根据不同的放疗方式选择不同的CT扫描条件对放疗计划的剂量计算及分布具有重要的临床意义。

Objective To analyze the influences of different CT scanning conditions on the dose calculation of CyberKnife.Methods The CT images of Lucy in different scanning tube voltages(80,100,120 and 140 kV)and tube currents(150 and 300 mA),were acquired by Philips big bore CT.Different radiotherapy plans were designed and calculated by the CyberKnife Multiplan■system.The effects of different scanning conditions on the CT values of the region of interest,the dose values of the region of interest,the target region and the outer shell layer of the target region were analyzed.Statistical analysis was performed using SPSS 22.0 software.Results The tube voltage had statistically significant effects on the CT values(P<0.05)and the CT values in the region of interest were negatively correlated with the tube voltage in case the tube current was kept constant.CT scanning conditions had different degrees of influences on the dose distribution.The higher the tube current,the more compact the dose distribution and the steeper the dose drop,while there was no statistically significance found;the effects of different tube voltages on D50 of the target areas and normal tissue(right eye)were statistically significant(P<0.05),indicating that tube voltage could alter the dose distribution of the target areas and normal tissue.Conclusion Scanning conditions influence CT values directly,and also have effects on the dose calculation and distribution of radiotherapy planning.Therefore,the selection of CT scanning conditions for different radiotherapy modalities is of great clinical importance for dose calculation and distribution in radiotherapy planning.