评估肺癌调强放疗中针对特定射束的 PTV 的 OAR 剂量节省和计划稳健性。

Evaluation of OAR dose sparing and plan robustness of beam-specific PTV in lung cancer IMRT treatment.

机构信息

Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.

Department of Medical Physics, School of Physics and Technology, Wuhan University, Wuhan, 430072, China.

出版信息

Radiat Oncol. 2020 Oct 17;15(1):241. doi: 10.1186/s13014-020-01686-1.

DOI:10.1186/s13014-020-01686-1

PMID:33069253

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7568374/

Abstract

PURPOSE

Margins are employed in radiotherapy treatment planning to mitigate the dosimetric effects of geometric uncertainties for the clinical target volume (CTV). Here, we proposed a margin concept that takes into consideration the beam direction, thereby generating a beam-specific planning target volume (BSPTV) on a beam entrance view. The total merged BSPTV was considered a target for optimization. We investigated the impact of this novel approach for lung intensity-modulated radiotherapy (IMRT) treatment, and compared the treatment plans generated using BSPTV with general PTV.

METHODS AND MATERIALS

We generated the BSPTV by expanding the CTV perpendicularly to the incident beam direction using the 2D version of van Herk's margin concept. The BSPTV and general PTV margin were analyzed using digital phantom simulation. Fifteen lung cancer patients were used in the planning study. First, all patient targets were performed with the CTV projection area analysis to select the suitable beam angles. Then, BSPTV was generated according to the selected beam angles. IMRT plans were optimized with the general PTV and BSPTV as the target volumes, respectively. The dosimetry metrics were calculated and evaluated between these two plans. The plan robustness of both plans for setup uncertainties was evaluated using worst-case analysis.

RESULTS

Both general PTV and BSPTV plans satisfied the CTV coverage. In addition, the BSPTV plans improved the sparing of high doses to target-surrounding lung tissues compared to the general PTV plans. Both D of Ring PTV and Ring BSPTV were significantly lower in BSPTV plans (38.89 Gy and 39.43 Gy) compared to the general PTV plans (40.27 Gy and 40.68 Gy). The V20, V5, and mean lung dose of the affected lung were significant lower in BSPTV plans (16.20%, 28.75% and 8.93 Gy) compared to general PTV plans (16.69%, 29.22% and 9.18 Gy). In uncertainty scenarios, about 80% of target coverage was achieved for both general PTV and BSPTV plans.

CONCLUSIONS

The results suggested that plan robustness can be guaranteed in both the BSPTV and general PTV plans. However, the BSPTV plan spared normal tissues, such as the lungs, significantly better compared to the general PTV plans.

摘要

目的

在放射治疗计划中使用边缘，以减轻临床靶区（CTV）的几何不确定性对剂量的影响。在这里，我们提出了一种考虑射束方向的边缘概念，从而在射束入口视图上生成特定射束的计划靶区（BSPTV）。总合并的 BSPTV 被认为是优化的目标。我们研究了这种新方法对肺调强放疗（IMRT）治疗的影响，并比较了使用 BSPTV 和一般 PTV 生成的治疗计划。

方法和材料

我们通过使用 van Herk 边缘概念的 2D 版本，将 CTV 垂直于入射射束方向扩展，生成 BSPTV。通过数字体模模拟分析 BSPTV 和一般 PTV 边缘。我们对 15 例肺癌患者进行了计划研究。首先，对所有患者的靶区进行 CTV 投影面积分析，以选择合适的射束角度。然后，根据选定的射束角度生成 BSPTV。分别以一般 PTV 和 BSPTV 为目标体积对 IMRT 计划进行优化。计算并评估了这两种计划之间的剂量学指标。使用最坏情况分析评估了两种计划在设置不确定性方面的计划稳健性。

结果

一般 PTV 和 BSPTV 计划均满足 CTV 覆盖要求。此外，与一般 PTV 计划相比，BSPTV 计划更好地保护了靶区周围肺组织免受高剂量照射。BSPTV 计划的 Ring PTV 和 Ring BSPTV 的 D 值（38.89Gy 和 39.43Gy）明显低于一般 PTV 计划（40.27Gy 和 40.68Gy）。BSPTV 计划中受影响肺的 V20、V5 和平均肺剂量（16.20%、28.75%和 8.93Gy）明显低于一般 PTV 计划（16.69%、29.22%和 9.18Gy）。在不确定性情况下，一般 PTV 和 BSPTV 计划均能达到约 80%的靶区覆盖。