Paronetto Chiara, den Toom Wilhelm, Milder Maaike T W, van Norden Yvette, Baak Rogier, Heijmen Ben J M, Méndez Romero Alejandra
Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands.
Department of Radiotherapy, Istituto Oncologico Veneto (IOV), Padova, Italy.
Front Oncol. 2023 Mar 8;13:1114737. doi: 10.3389/fonc.2023.1114737. eCollection 2023.
Using fiducial-marker-based robotic respiratory tumor tracking, we treated perihilar cholangiocarcinoma patients in the STRONG trial with 15 daily fractions of 4 Gy. For each of the included patients, in-room diagnostic-quality repeat CTs (rCT) were acquired pre- and post-dose delivery in 6 treatment fractions to analyze inter- and intrafraction dose variations. Planning CTs (pCTs) and rCTs were acquired in expiration breath-hold. Analogous to treatment, spine and fiducials were used to register rCTs with pCTs. In each rCT, all OARs were contoured, and the target was rigidly copied from the pCT based on grey values. The rCTs acquired were used to calculate the doses to be delivered through the treatment-unit settings. On average, target doses in rCTs and pCTs were similar. However, due to target displacements relative to the fiducials in rCTs, 10% of the rCTs showed PTV coverage losses of >10%. Although target coverages had been planned below desired values in order to protect OARs, many pre-rCTs contained OAR constraint violations: 44.4% for the 6 major constraints. Most OAR dose differences between pre- and post-rCTs were not statistically significant. The dose deviations observed in repeat CTs represent opportunities for more advanced adaptive approaches to enhancing SBRT treatment quality.
在STRONG试验中，我们使用基于基准标记的机器人呼吸肿瘤追踪技术，对肝门周围胆管癌患者进行了每日15次、每次4 Gy的治疗。对于纳入的每位患者，在6个治疗分次的剂量递送前和后获取了室内诊断质量的重复CT（rCT），以分析分次间和分次内的剂量变化。在呼气屏气时获取计划CT（pCT）和rCT。与治疗类似，使用脊柱和基准标记将rCT与pCT进行配准。在每个rCT中，勾勒出所有危及器官（OAR），并根据灰度值从pCT中刚性复制靶区。获取的rCT用于通过治疗单元设置计算要递送的剂量。平均而言，rCT和pCT中的靶区剂量相似。然而，由于rCT中靶区相对于基准标记的位移，10%的rCT显示计划靶体积（PTV）覆盖损失>10%。尽管为了保护OAR，靶区覆盖计划低于期望的值，但许多rCT前的图像存在OAR约束违规情况：6项主要约束中有44.4%。rCT前和后大多数OAR剂量差异无统计学意义。在重复CT中观察到的剂量偏差为采用更先进的自适应方法提高立体定向体部放疗（SBRT）治疗质量提供了机会。
