Effect of respiratory movement on the dose distribution in the TOMO therapy target area

Abstract

Objective To explore the effect of respiratory movement on the dose distribution in the TOMO therapy target area.

Methods The motion phantom was used to simulate human respiratory movement. The SNC patient analysis software was used to compare the films of the study group with those of the control group, and the effect of respiratory movement on the dose distribution in the TOMO target area was evaluated by the “pass rate” index.

Results Visual observation showed that the distribution of film gray in the head-foot direction (i.e., direction of movement) was significantly different with or without respiratory movement. Film analysis showed that the maximum deviation between the width of the target wrapping curve and the treatment plan value was about 2.4 mm at no respiratory movement and about 27.2 mm at respiratory movement; the penumbra width of the target area was 31 mm (head direction) and 28.5 mm (foot direction) at no respiratory movement and 39.7 mm (head direction) and 37 mm (foot direction) at respiratory movement; the “pass rate” of target dose distribution was only 12.3%.

Conclusion Respiratory movement has a great impact on the dose distribution in the TOMO target area in the direction of movement. When making clinical treatment plan, the impact of respiratory movement on the dose distribution in the TOMO target area can not be ignored.

Abstract

摘要： 目的 了解呼吸运动对TOMO靶区剂量分布造成的影响。 方法 使用运动模体模拟人体呼吸运动。使用 SNC Patient分析软件将研宄组胶片与对照组胶片进行比较, 通过“通过率”指标评价呼吸运动对TOMO靶区剂量分布 造成的影响。 结果 肉眼即可观察到有、无呼吸运动时胶片灰度在头-脚方向 (即运动方向)上的分布存在不同; 胶片 分析得到的无呼吸运动时靶区包绕曲线宽度与治疗计划值最大偏差约2.4 mm, 有呼吸运动时靶区包绕曲线宽度与治 疗计划值最大偏差约27.2 mm; 无呼吸运动时靶区半影宽度为31 mm(头方向)、28.5 mm(脚方向), 有呼吸运动时靶区 半影宽度为39.7 mm(头方向) 、37 mm(脚方向); 靶区剂量分布“通过率”仅为12.3%。 结论 呼吸运动在运动方向上 对TOMO靶区剂量分布造成的影响较大, 临床制定治疗计划时呼吸运动对TOMO靶区剂量分布的影响不容忽视。