射波刀影像追踪中X射线曝光条件对脊柱追踪错误节点及辐射剂量的影响

Effect of X-ray exposure parameters on the false-node rate and radiation dose in CyberKnife spine tracking

目的 研究和探讨射波刀脊柱追踪影像引导放疗中X射线曝光条件与错误节点比率的关系.方法 利用脊柱追踪放疗计划,采用不同X射线曝光条件对体模进行影像引导定位,观察脊柱追踪错误节点比率及体模表面吸收剂量的变化规律,确定X射线曝光条件与脊柱追踪错误节点比率之间是否存在优化曝光剂量.结果 脊柱追踪错误节点比率随着X射线曝光条件增加而降低,初期明显,但随着曝光条件的增加到一定水平,脊柱追踪错误节点比率不再降低；体模表面吸收剂量随着X射线曝光条件增加而增加；在≤5％的错误节点标准范围内,当平均错误节点为2.77％、1.07％、1.0％时,体模表面吸收剂量分别为0.11、0.26、0.31～0.46 mGy,相差1～3倍.结论 在射波刀影像引导放疗中,X射线曝光条件与脊柱追踪错误节点之间存在优化曝光剂量,使用最优X射线影像曝光剂量可大幅降低患者辐射剂量,对放疗患者的辐射防护具有非常重要的意义.

Objective To explore the relationship of X-ray exposure parameters and false-node rate during image-guidance treatment with CyberKnife spine tracking.Methods Using spine tracking planning on a chest phantom,several combinations of X-ray exposure parameters were used to locate.The false-node ratio and the surface absorbed dose were investigated and the radiation dose was optimized.Results The false-node ratio and surface absorbed radiation dose decreased when the X-ray exposure parameters increased until they saturated.In the range of ≤5.0％ false-node rate,the surface absorbed radiation dose was 0.11,0.26 mGy,and 0.31-0.46 mGy,when the false-node rate was 2.77％,1.07％and 1.0％,respectively.Conclusions In image-guided treatment of CyberKnife,the radiation dose would be optimized,and the patient＇s radiation dose would be reduced greatly,which is important to protect the patients.