Zou Wei, Kurtz Goldie, Nakib Mayisha, Burgdorf Brendan, Alp Murat, Li Taoran, Lustig Robert, Xiao Ying, Dong Lei, Kassaee Alireza, Alonso-Basanta Michelle
Department of Radiation Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA.
Int J Part Ther. 2021 Jan 28;7(3):34-45. doi: 10.14338/IJPT-20-00009.1. eCollection 2021 Winter.
The intracranial skull-base meningioma is in proximity to multiple critical organs and heterogeneous tissues. Steep dose gradients often result from avoiding critical organs in proton treatment plans. Dose uncertainties arising from setup errors under image-guided radiation therapy are worthy of evaluation.
Fourteen patients with skull-base meningioma were retrospectively identified and planned with proton pencil beam scanning (PBS) single-field uniform dose (SFUD) and multifield optimization (MFO) techniques. The setup uncertainties were assigned a probability model on the basis of prior published data. The impact on the dose distribution from nominal 1-mm and large, less probable setup errors, as well as the cumulative effect, was analyzed. The robustness of SFUD and MFO planning techniques in these scenarios was discussed.
The target coverage was reduced and the plan dose hot spot increased by all setup uncertainty scenarios regardless of the planning techniques. For 1 mm nominal shifts, the deviations in clinical target volume (CTV) coverage D99% was -11 ± 52 cGy and -45 ± 147 cGy for SFUD and MFO plans. The setup uncertainties affected the organ at risk (OAR) dose both positively and negatively. The statistical average of the setup uncertainties had <100 cGy impact on the plan qualities for all patients. The cumulative deviations in CTV D95% were 1 ± 34 cGy and -7 ± 18 cGy for SFUD and MFO plans.
It is important to understand the impact of setup uncertainties on skull-base meningioma, as the tumor target has complex shape and is in proximity to multiple critical organs. Our work evaluated the setup uncertainty based on its probability distribution and evaluated the dosimetric consequences. In general, the SFUD plans demonstrated more robustness than the MFO plans in target coverages and brainstem dose. The probability-weighted overall effect on the dose distribution is small compared to the dosimetric shift during single fraction.
颅内颅底脑膜瘤靠近多个关键器官和异质组织。在质子治疗计划中，为避开关键器官常常会产生陡峭的剂量梯度。图像引导放射治疗下因摆位误差引起的剂量不确定性值得评估。
回顾性确定了14例颅底脑膜瘤患者，并采用质子笔形束扫描（PBS）单野均匀剂量（SFUD）和多野优化（MFO）技术进行治疗计划设计。根据先前发表的数据为摆位不确定性赋予概率模型。分析了名义上1毫米以及较大但可能性较小的摆位误差对剂量分布的影响以及累积效应。讨论了在这些情况下SFUD和MFO计划技术的稳健性。
无论采用何种计划技术，所有摆位不确定性情况均导致靶区覆盖减少且计划剂量热点增加。对于名义上1毫米的移位，SFUD和MFO计划的临床靶区体积（CTV）覆盖D99%的偏差分别为-11±52 cGy和-45±147 cGy。摆位不确定性对危及器官（OAR）剂量有正向和负向影响。摆位不确定性的统计平均值对所有患者的计划质量影响<100 cGy。SFUD和MFO计划的CTV D95%累积偏差分别为1±34 cGy和-7±18 cGy。
了解摆位不确定性对颅底脑膜瘤的影响很重要，因为肿瘤靶区形状复杂且靠近多个关键器官。我们的工作基于其概率分布评估了摆位不确定性，并评估了剂量学后果。总体而言，在靶区覆盖和脑干剂量方面，SFUD计划比MFO计划表现出更强的稳健性。与单次分割期间的剂量学移位相比，剂量分布的概率加权总体影响较小。
