Department of Radiation Oncology, Academic Medical Center, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2012 Jul 15;83(4):e557-62. doi: 10.1016/j.ijrobp.2011.12.055. Epub 2012 May 23.
To determine whether dose-guided radiotherapy (i.e., online recalculation and evaluation of the actual dose distribution) can improve decision making for lung cancer patients treated with stereotactic body radiotherapy.
For this study 108 cone-beam computed tomography (CBCT) scans of 10 non-small-cell lung cancer patients treated with stereotactic body radiotherapy were analyzed retrospectively. The treatment plans were recalculated on the CBCT scans. The V(100%) of the internal target volume (ITV) and D(max) of the organs at risk (OARs) were analyzed. Results from the recalculated data were compared with dose estimates for target and OARs by superposition of the originally planned dose distribution on CBCT geometry (i.e., the original dose distribution was assumed to be spatially invariant).
Before position correction was applied the V(100%) of the ITV was 100% in 65% of the cases when an ITV-PTV margin of 5 mm was used and 52% of the cases when a margin of 3 mm was used. After position correction, the difference of D(max) in the OARs with respect to the treatment plan was within 5% in the majority of the cases. When the dose was not recalculated but estimated assuming an invariant dose distribution, clinically relevant errors occurred in both the ITV and the OARs.
Dose-guided radiotherapy can be used to determine the actual dose in OARs when the target has moved with respect to the OARs. When the workflow is optimized for speed, it can be used to prevent unnecessary position corrections. Estimating the dose by assuming an invariant dose instead of recalculation of the dose gives clinically relevant errors.
确定剂量引导放疗（即在线重新计算和评估实际剂量分布）是否可以改善立体定向体部放疗治疗的肺癌患者的决策。
本研究回顾性分析了 10 例接受立体定向体部放疗的非小细胞肺癌患者的 108 次锥形束 CT（CBCT）扫描。对 CBCT 扫描进行了重新计算。分析了内部靶区（ITV）的 V（100%）和危及器官（OARs）的 D（max）。通过将原始计划剂量分布叠加到 CBCT 几何形状上（即，假设原始剂量分布在空间上是不变的）来比较重新计算数据的结果与靶区和 OARs 的剂量估计值。
在未进行位置校正之前，当 ITV-PTV 边界为 5mm 时，65%的情况下 ITV 的 V（100%）为 100%，当边界为 3mm 时，52%的情况下 ITV 的 V（100%）为 100%。进行位置校正后，在大多数情况下，OARs 的 D（max）差异在 5%以内。当不重新计算剂量而是假设剂量分布不变进行估计时，ITV 和 OARs 都会出现临床相关误差。
当靶区相对于 OARs 移动时，剂量引导放疗可用于确定 OARs 中的实际剂量。当工作流程为速度优化时，它可用于防止不必要的位置校正。通过假设剂量不变而不是重新计算剂量来估计剂量会导致临床相关的误差。
