Department of Radiotherapy, Division of Radiation Physics, State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu 610041, P.R. China.
Department of Radiotherapy, Jingzhou Central Hospital, the Second Clinical Medical College, Yangtze University, Jingzhou 434020, P.R. China.
J Radiat Res. 2020 May 22;61(3):457-463. doi: 10.1093/jrr/rraa007.
The purpose of the study was to quantify local setup errors and evaluate the planning target volume (PTV) margins for sub-regions in cone-beam computed tomography (CBCT)-guided post-mastectomy radiation therapy (PMRT). The local setup errors of 20 patients undergoing CBCT-guided PMRT were analysed retrospectively. Image registration between CBCT and planning CT was performed using four sub-regions of interest (ROIs): the supraclavicular area (SROI), ipsilateral chest wall region (CROI), ipsilateral chest wall plus supraclavicular region (SROI + CROI) and vertebral region (TROI). Bland-Altman analysis, correlation, local setup errors and PTV margins among these ROIs were evaluated. There was no significant consistency or correlation for registration results between the TROI and the CROI or SROI regions on any translational axis. When using the SROI + CROI as the ROI, the systematic error (Σ) and random error (σ) of the local setup errors for the CROI region were 1.81, 1.19 and 1.76 mm and 1.84, 2.64 and 3.00 mm along the medial-lateral (ML), superior-inferior (SI) and anterior-posterior (AP) directions, respectively. The PTV margins for the CROI region were 5.80, 4.82 and 6.50 mm. The Σ and σ of the local setup errors for the SROI region were 1.29, 1.15 and 0.77 mm and 1.96, 2.65 and 2.2 mm, respectively, and the PTV margins were 4.59, 4.73 and 3.47 mm. Large setup errors and local setup errors occur in PMRT. The vertebral body should not be a position surrogate for the supraclavicular region or chest wall. To compensate for the local setup errors, different PTV margins are required, even with CBCT guidance.
本研究旨在量化锥形束 CT（CBCT）引导下乳腺癌根治术后放疗（PMRT）中局部摆位误差，并评估计划靶区（PTV）的各亚区边界。回顾性分析了 20 例接受 CBCT 引导下 PMRT 的患者的局部摆位误差。通过四个感兴趣区（ROI）：锁骨上区（SROI）、同侧胸壁区（CROI）、同侧胸壁加锁骨上区（SROI+CROI）和椎体区（TROI），对 CBCT 与计划 CT 之间的图像进行配准。评估了这些 ROI 之间的 Bland-Altman 分析、相关性、局部摆位误差和 PTV 边界。在任何平移轴上，TROI 与 CROI 或 SROI 区域的注册结果均无显著一致性或相关性。当使用 SROI+CROI 作为 ROI 时，CROI 区域的局部摆位误差的系统误差（Σ）和随机误差（σ）分别为 1.81、1.19 和 1.76mm 以及 1.84、2.64 和 3.00mm，沿内外侧（ML）、上下（SI）和前后（AP）方向。CROI 区域的 PTV 边界为 5.80、4.82 和 6.50mm。SROI 区域的Σ和σ的局部摆位误差分别为 1.29、1.15 和 0.77mm 以及 1.96、2.65 和 2.2mm，PTV 边界分别为 4.59、4.73 和 3.47mm。在 PMRT 中会出现较大的摆位误差和局部摆位误差。椎体不应作为锁骨上区或胸壁的替代位置。为了补偿局部摆位误差，即使有 CBCT 引导，也需要不同的 PTV 边界。
