Jang Seong Soon, Huh Gil Ja, Park Suk Young, Yang Po Song, Cho Eun Youn
Department of Radiation Oncology, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
Department of Radiation Oncology, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
Phys Med. 2014 Sep;30(6):682-9. doi: 10.1016/j.ejmp.2014.05.005. Epub 2014 Jun 3.
The purpose of this study was to evaluate the impacts of respiratory gating and different gating windows (GWs) on lung dosimetry in stereotactic body radiotherapy (SBRT) for lung cancer. Gated SBRT plans were developed using the four-dimensional computed tomography data from 17 lung cancer patients treated with SBRT. Using amplitude-based end-exhalation gating, we established 2 fixed GWs with approximate duty cycles of 50% (50% GW) and 25% (25% GW), respectively, for this study. For highly mobile tumors (3D mobility > 10 mm), additional benefits in lung-dose reductions were achieved with the 25% GW, as a result of inadequate mobility and planning target volume reductions obtained with the 50% GW. In these tumors, the absolute differences compared to the non-gated and 50% gated plans, were 0.5 Gy and 0.33 Gy for the mean lung dose and 1.11% and 0.71% for the V20, respectively. Dosimetric benefits were achieved with the 50% GW, compared with the non-gated plan, for tumors with both low mobility and small volume (gross tumor volume ≤ 10 cc). Among the identified predictive factors of dosimetric benefits, the lateral distance from midspinal canal and the motion range in anterior-posterior direction might be stronger factors because of their correlations with many of the lung-dose parameters and greater predictive capacity. The results of the present study might facilitate the selection of appropriate patients and the optimal GW according to the tumor characteristics for gated lung SBRT.
本研究的目的是评估呼吸门控和不同门控窗（GWs）对肺癌立体定向体部放疗（SBRT）中肺部剂量测定的影响。使用17例接受SBRT治疗的肺癌患者的四维计算机断层扫描数据制定了门控SBRT计划。在本研究中，我们采用基于幅度的呼气末门控，分别建立了近似占空比为50%（50%GW）和25%（25%GW）的2个固定门控窗。对于高移动性肿瘤（三维移动性>10mm），由于50%GW的移动性不足和计划靶体积减小，25%GW在降低肺部剂量方面有额外益处。在这些肿瘤中，与非门控和50%门控计划相比，平均肺剂量的绝对差异分别为0.5Gy和0.33Gy，V20的绝对差异分别为1.11%和0.71%。对于低移动性和小体积（肿瘤总体积≤10cc）的肿瘤，与非门控计划相比，50%GW在剂量测定方面有获益。在已确定的剂量测定获益预测因素中，距脊髓中线的横向距离和前后方向的运动范围可能是更强的因素，因为它们与许多肺部剂量参数相关且预测能力更强。本研究结果可能有助于根据肿瘤特征为门控肺部SBRT选择合适的患者和最佳的GW。
