立体定向放疗动态剂量算法及其在射波刀肺癌治疗中的应用研究

The effects of respiratory motion on the accuracy of stereotactic body radiotherapy (SBRT) were significant. At present, the internal planning target volume could not calculate the accurate dose of the tumors and organs at risk which are moved with the respiratory. Although recent researches about 4D accumulated dose algorithm shows that it can eliminate the systematic errors such as changes in tissue density with respiratory motion, it still cannot eliminate the random errors caused by the interplay effect between respiratory motion and treatment plan execution sequence. Our previous study found that the above mentioned random errors for the cyberknife SBRT can lead to the dose delivered to the target and organs at risk exceed 30% of the prescribed dose. In order to solve this problem, this project creatively proposes a dynamically accumulated dose algorithm that combines the 4DCT image and the treatment plan execution sequence to calculate the actual accumulated dose received by the patient. And this dose algorithm could be used to correct the actual dose of the cyberknife static and dynamic tracing SBRT. The new dose algorithm will effectively reduce the impact of systemic errors such as changes in tissue density with respiratory motion and random errors caused by the interplay effect between respiratory motion and treatment plan execution sequence, thereby improving the accuracy of dose calculation of tumors and organs at risk of lung cancer SBRT.

呼吸运动对肺部立体定向放疗(SBRT)计划实施的准确性影响显著。目前内运动靶区外扩法，无法准确计算随呼吸运动的肿瘤和危及器官的真实剂量。最近研究中采用的4D累积剂量算法，虽然可以消除随呼吸运动的组织密度变化等系统误差，但仍无法消除呼吸运动与计划执行时序之间交互作用所引入的随机误差。我们前期研究发现，射波刀SBRT治疗时上述随机误差可导致靶区和危及器官剂量误差超过处方剂量的30%。为解决上述问题，本项目创新性地提建出建立4DCT影像和治疗计划执行时序相结合的动态剂量算法模型，计算患者接受的真实累积剂量，并用于修正射波刀静态和动态呼吸追踪SBRT的计划剂量。新算法将有效降低组织密度变化等系统误差和呼吸运动与治疗时序交互作用引入的随机误差对累积剂量的影响，从而提升SBRT中随呼吸运动的肿瘤和危及器官的剂量计算的精度。

呼吸运动对肺部立体定向放射治疗(SBRT)计划实施的准确性影响显著。目前临床广泛采用的内运动靶区外扩法，其实无法准确计算随呼吸运动的肿瘤和危及器官的真实剂量。近年来研究中采用的4D累积剂量算法，虽然可以消除随呼吸运动的组织密度变化等系统误差影响，但仍无法消除呼吸运动与计划执行时序间的交互作用所引入的随机误差。我们前期的研究发现，射波刀SBRT治疗时上述随机误差可导致靶区和危及器官的剂量误差超过处方剂量的30%。为解决上述问题，本项目提出建立利用4DCT和治疗计划执行时序的动态剂量算法模型，计算患者接受的真实累积剂量，并用于修正受呼吸运动影响的SBRT治疗计划剂量。新算法有效评估了组织密度变化等系统误差和呼吸运动与治疗时序交互作用引入的随机误差对累积剂量的影响，从而提升SBRT中随呼吸运动的肿瘤和危及器官的剂量计算的精度。本项目完成了4D剂量计算算法的模型，并开展了相应实验研究，研究显示本模型可有效评估SBRT计划受呼吸运动的影响，为临床评估提供有效数据支持。本项目从肿瘤放疗临床需求出发，解决了临床亟需解决的实际问题，具有重要的科学意义和广阔的应用前景。