Department of Medical Physics, Portsmouth Hospitals University NHS Trust, Portsmouth, UK; Division of Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.
Department of Medical Physics, Portsmouth Hospitals University NHS Trust, Portsmouth, UK.
Phys Med. 2022 Aug;100:112-119. doi: 10.1016/j.ejmp.2022.06.015. Epub 2022 Jul 4.
Adaptive radiotherapy relies of rapid re-contouring, online more so than offline. Intra-patient contour propagation via non-rigid registration offers a solution but can be of limited accuracy. However, the dosimetric significance of the inaccuracies is unknown. Here we evaluate the dosimetric reliability of contours generated by different commercially-available software packages.
Planning CT contours for ten head and neck cancer patients were propagated via five commercial packages to five CBCT scans acquired throughout treatment. The treatment plan was recalculated on each of the CBCTs for each set of propagated contours, and DVH parameters extracted for the spinal cord, brainstem, parotids and larynx. The propagated contours were compared to two gold standard contours: contours manually outlined and a consensus STAPLE contours generated from the propagated contours. Geometrical similarity was evaluated using mean distance to agreement (mDTA), Hausdorff distance, centroid agreement and Dice similarity coefficient. Dosimetric reliability was assessed against clinical constraints and comparing via the intraclass correlation coefficient (ICC).
All propagated contours were similar to the STAPLE (mDTA < 1.0 mm) whilst larger differences were seen for the manual contours (mDTA < 3.0 mm). The dosimetric comparison showed that the propagated contours gave excellent dose estimates for most organs. The spinal cord reliability was moderate (ICC > 0.66).
Large differences in geometric metrics rarely had a statistically significant impact on DVH parameters for the OARs studied. For that reason, propagated contours on treatment CBCT images are suitable for estimating dose to the OARs.
自适应放疗依赖于快速重新轮廓勾画，在线比离线更重要。通过非刚性配准进行的患者内轮廓传播提供了一种解决方案，但准确性可能有限。然而，这种不准确性的剂量学意义尚不清楚。在这里，我们评估了不同商业软件包生成的轮廓的剂量学可靠性。
通过五个商业软件包将十个头颈部癌症患者的计划 CT 轮廓传播到整个治疗过程中采集的五个 CBCT 扫描中。针对每个患者的每个传播轮廓集，对每个 CBCT 重新计算了治疗计划，并提取了脊髓、脑干、腮腺和喉咙的剂量学体积直方图（DVH）参数。将传播轮廓与两个金标准轮廓进行比较：手动勾画的轮廓和从传播轮廓生成的共识 STAPLE 轮廓。使用平均距离一致性（mDTA）、Hausdorff 距离、质心一致性和 Dice 相似系数评估几何相似性。通过组内相关系数（ICC）评估剂量学可靠性并进行比较。
所有传播轮廓都与 STAPLE 相似（mDTA<1.0mm），而手动轮廓的差异较大（mDTA<3.0mm）。剂量学比较表明，对于大多数器官，传播轮廓给出了极好的剂量估计。脊髓的可靠性为中度（ICC>0.66）。
在研究的 OAR 中，几何指标的较大差异很少对 DVH 参数产生统计学上的显著影响。因此，治疗 CBCT 图像上的传播轮廓适用于估计 OAR 的剂量。
