Cancer Research UK, RadNet Cambridge, Department of Medical Physics, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
Med Dosim. 2022;47(3):264-272. doi: 10.1016/j.meddos.2022.04.004. Epub 2022 May 23.
Compare the robustness of wide tangents (WT) and volumetric modulated arc therapy (VMAT) using different skin flash approaches in breast and nodal radiotherapy. Ten patients treated with WT using 2-cm flash were replanned with VMAT using no flash (NF), manual 2-cm flash (MF), and robust optimization (RO). Plan robustness was assessed for target coverage and organs at risk (OAR) by recalculating on 5 deformed CT scans (SOM1-5), daily cone beam (CBCT), and by shifting the isocenter 5 mm. VMAT NF gave poor coverage of CTVp with its smallest change of -3.2% for V on CBCT. VMAT RO plans showed the least variations in target coverage loss compared to WT and VMAT MF which dropped as anatomical swelling increased. CTVp D decreased on CBCT and increased most for VMAT MF plans (case max increase +3.3 Gy), whereas VMAT RO plans were relatively stable (case max increase +1.2 Gy). OAR dose changed little with anatomical changes (isocenter shifts more important with medial, posterior, and inferior increasing dose). Nodal coverage was superior for VMAT which led to the WT being less robust for coverage toward both geometric and anatomical uncertainties. All techniques except NF plans gave high levels of coverage under minor uncertainties. VMAT RO was highly robust for target coverage for anatomical changes. Manually editing control points on VMAT plans was time-consuming and less predictable. CBCT anatomical changes were modest resulting in small delivered dose changes. OAR dose changes were small with no significant differences between techniques.
比较宽切线（WT）和容积调制弧形治疗（VMAT）在乳腺癌和淋巴结放疗中使用不同皮肤闪光方法的稳健性。使用 2cm 闪光的 10 名 WT 治疗患者使用无闪光（NF）、手动 2cm 闪光（MF）和稳健优化（RO）重新规划 VMAT。通过在 5 个变形 CT 扫描（SOM1-5）、每日锥形束 CT（CBCT）和将等中心点移动 5mm 来重新计算，评估目标覆盖和危及器官（OAR）的计划稳健性。VMAT NF 对 CTVp 的覆盖较差，其在 CBCT 上的最小变化为 -3.2%的 V。与 WT 和 VMAT MF 相比，VMAT RO 计划在靶区覆盖丢失方面表现出最小的变化，随着解剖肿胀的增加而减少。CTVp D 在 CBCT 上降低，VMAT MF 计划增加最多（病例最大增加+3.3Gy），而 VMAT RO 计划相对稳定（病例最大增加+1.2Gy）。OAR 剂量随解剖变化变化不大（等中心点变化对于内侧、后侧和下侧增加剂量更重要）。VMAT 对淋巴结的覆盖更好，导致 WT 在覆盖几何和解剖不确定性方面的稳健性降低。除 NF 计划外，所有技术在较小的不确定性下都能提供较高的覆盖水平。VMAT RO 对目标覆盖的解剖变化具有高度稳健性。手动编辑 VMAT 计划的控制点既耗时又不可预测。CBCT 解剖变化适度，导致剂量变化较小。OAR 剂量变化较小，各技术之间无显著差异。
