呼吸运动对调强放疗影响的实验研究

目的 :评价静态调强放疗治疗肺癌等运动幅度较大肿瘤的可行性。方法 :应用自行研制的运动体模系统模拟呼吸运动 ,测量不同运动幅度及不同运动方向对基于多叶光栅的静态调强放疗射束半影、剂量分布及绝对剂量的影响。结果 :靶区运动明显增加了射野在运动方向的半影 ,导致了低剂量区面积增大及高剂量区不确定性的增加 ,但70 %～ 90 %的等剂量线变化不显著。虽然不同情况下各测量点的剂量有不同程度的变化 ,但若将运动等不确定性因素考虑在内 ,多次测量后总体变化幅度均在允许的范围之内。结论 :靶区运动加宽了射束的半影 ,但在适当补偿运动等影响靶区确定的因素后 ,应用静态调强放疗治疗周期性运动的肿瘤是可行的

Study on effects of respiration to intensity modulated radiotherapy

OBJECTIVE: To evaluate the feasibility of static intensity modulated radiotherapy (IMRT) treating lung tumor with greater motion magnitude. METHODS:One way breathing was simulated by using self-made motion phantom. The effects of different motion magnitudes and different moving directions on beam penumbra, dose distribution, and absolute point dose of static IMRT based on multi-leaf collimator (MLC) were measured.RESULTS:Target motion increased the beam penumbra significantly along moving direction, which led to the area covered by lower dose line increased and the area surrounded by higher dose line varied more greatly. However, the area surrounded by 70%-90% dose lines varied little. Though every point dose varied under different conditions,the general varying range of point absorbed dose after multi-fractionation measurements was acceptable, given uncertainty factors eg. organ motion being included. CONCLUSIONS:Though organ motion makes beam penumbra wider, static IMRT based on MLC is feasible to treat tumors with regular motion after every uncertainty factor which affects the definition of target is compensated appropriately.