Abstract Whole-brain radiotherapy (WBRT) with hippocampal avoidance improves neurocognitive function deterioration. To improve both planning and treatment efficiency, we investigated the feasibility of using the coplanar volumetric-modulated arc therapy (VMAT) technique with various head flexion angles for hippocampal avoidance during WBRT. Six patients with brain metastases were selected for the study. We rotated patient CT images by 90° and changed the couch angle to simulate different head flexion angles. The plan with a head angle of 0° had the lowest planning target volume (PTV) coverage and the highest normal organ dose (i.e., hippocampus and bilateral lenses). When the angle was equal to or greater than 15°, the maximum dose of the hippocampus and the PTV V30 met all dose constraints. The results obtained with head angles equal to or greater than 25° were better than those obtained at angles below 25° with the obviously decreased dose of the bilateral lenses. The VMAT treatment plans of each patient were computed under various head flexion angles using the Eclipse Treatment Planning System. The study demonstrated that 15° is the minimum head flexion angle that should be adopted in clinical practice. For better dose coverage and uniformity for whole-brain PTV and dose reduction of critical organs, the study results suggested utilizing a head angle equal to or greater than 25°, while ensuring that patient comfort is maintained with larger head flexion angles. Compared with non-coplanar linac-based techniques, a tilted head angle with the coplanar VMAT technique not only reduces plan complexity but also improves treatment efficiency.

中文翻译：

---

容积调制弧形疗法对海马回避型全脑放疗中不同头部屈曲角度的评价

摘要 具有海马回避功能的全脑放疗 (WBRT) 可改善神经认知功能的恶化。为了提高计划和治疗效率，我们研究了在 WBRT 期间使用具有不同头部屈曲角度的共面体积调制弧形疗法 (VMAT) 技术来避免海马的可行性。选择了 6 名脑转移患者进行研究。我们将患者 CT 图像旋转 90° 并改变床角以模拟不同的头部屈曲角度。头角为 0° 的计划具有最低的计划靶体积 (PTV) 覆盖率和最高的正常器官剂量（即海马体和双侧晶状体）。当角度等于或大于15°时，海马和PTV V30的最大剂量满足所有剂量限制。头角等于或大于25°获得的结果优于角度小于25°获得的结果，双侧晶状体的剂量明显减少。使用 Eclipse 治疗计划系统在不同的头部屈曲角度下计算每位患者的 VMAT 治疗计划。研究表明，15°是临床实践中应采用的最小头部屈曲角度。为了更好地覆盖全脑 PTV 和减少关键器官的剂量，研究结果建议使用等于或大于 25° 的头部角度，同时确保通过较大的头部弯曲角度保持患者的舒适度。与基于非共面直线加速器的技术相比，