射波刀治疗中追踪肿瘤边界缩放对肺追踪定位参数的影响

Influence of tracking tumor boundary scaling on Xsight lung tracking localization parameter in Cyberknife treatment

目的:探讨射波刀肺追踪放疗中追踪肿瘤边界缩放对肺追踪定位参数的影响,以提高肺追踪定位成功率。方法:使用肺追踪动态模体,以模拟肿瘤作为追踪肿瘤制订肺追踪放疗计划,然后依次间隔1 mm缩放模拟肿瘤边界至5 mm,制订不同模拟肿瘤肺追踪放疗计划,最后对放疗计划进行肺追踪定位,观察肺追踪定位参数dxAB(追踪肿瘤成像中心在实时影像A、B上下平移方向距离差)、Conference(实时影像追踪肿瘤的可信度)、Coverage(呼吸模型对模拟肿瘤运动范围的覆盖程度)值的变化。结果:模拟肿瘤边界未缩放时,dxAB、Conference、Coverage值分别为0.39 mm、100%、76.14%;随着模拟肿瘤边界顺序缩放,dxAB值呈不规则波动增大趋势,模拟肿瘤边界内收时更为明显,模拟肿瘤边界内收与外放时dxAB总平均值分别为0.67、0.53 mm;Conference值始终保持不变(100%);Coverage值呈平稳波动趋势,平均值为70%,波动幅度不超过9%。结论:追踪肿瘤靶区(gross tumor volume,GTV)边界缩放可引起肺追踪定位参数的不同改变,制订射波刀肺追踪放疗计划时,追踪肿瘤应以肿瘤GTV边界为标准。

Objective To investigate the effect of tracing tumor boundary scaling on Cyberknife Xsight lung tracking location parameter to enhance the success rate of the lung tracking location.Methods With LTT dynamic phantom,the Xsight lung tracking treatment plan was designed for the tumor phantom.Then the tumor phantom boundaries were scaled to 5 mm in 1 mm standard order,and different Xsight lung tracking treatment plans were made for the tumor phantom boundary scaling.Finally,all of the Xsight lung tracking treatment plans only for image location and respiration model building parts were performed to observe the changes of dxAB,Conference and Coverage values.Results The dxAB,Conference,and Coverage values were 0.39 mm,100%,and 76.14%respectively,when the tumor phantom boundary was not scaled.The dxAB values showed a trend of waving-increasing along with the tumor phantom boundary scaling,especially when the tumor phantom boundary was shrank.When the tumor phantom boundary was shrank and expanded,the total mean dxAB was 0.67 and 0.53 mm respectively;the Conference value remained constant(100%);the Coverage value showed a stable waving with an average of 70%,and the waving range did not exceed 9%.Conclusion Tracking tumor GTV boundary scaling can lead to a decrease of the accuracy on the Xsingt lung tracking location.When designing the Xsight lung tracking plan,the tumor GTV boundary should be used as a standard of tracking the tumor.