Kang Chen-Lin, Lee Tsair-Fwu, Chan Shan-Ho, Liu Shyh-Chang, Wang Jui-Chu, Tsai Cheng-Hsiang, Liao Kuan-Cho, Fang Fu-Min, Chang Liyun, Huang Chun-Chieh
Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Department of Medical Imaging and Radiology, Shu-Zen Junior College of Medicine and Management, Kaohsiung, Taiwan.
Cancer Manag Res. 2021 Jan 5;12:13599-13606. doi: 10.2147/CMAR.S283746. eCollection 2020.
Maintaining immobilization to minimize spine motion is very important during salvage stereotactic ablative radiation therapy (SABR) for recurrent head and neck cancer. This study aimed to compare the intrafractional motion between two immobilization methods.
With a spine tracking system for image guiding, 9094 records from 41 patients receiving SABR by CyberKnife were obtained for retrospective comparison. Twenty-one patients were immobilized with a thermoplastic mask and headrest (Group A), and another 20 patients used a thermoplastic mask and headrest together with a vacuum bag to support the head and neck area (Group B). The intrafractional motion in the X (superior-inferior), Y (right-left), Z (anterior-posterior) axes, 3D (three-dimensional) vector, Roll, Pitch and Yaw in the two groups was compared. The margins of the planning target volume (PTV) to cover 95% intrafractional motion were evaluated.
The translational movements in the X-axis, Y-axis, and 3D vector in Group A were significantly smaller than in Group B. The rotational errors in the Roll and Yaw in Group A were also significantly smaller than those in Group B; conversely, those in the Pitch in Group A were larger. To cover 95% intrafractional motion, margins of 0.96, 1.55, and 1.51 mm in the X, Y and Z axes, respectively were needed in Group A, and 1.06, 2.86, and 1.34 mm, respectively were required in Group B.
The immobilization method of thermoplastic mask and head rest with vacuum bag did not provide better immobilization than that without vacuum bag in most axes. The clinical use of 2 mm as a margin of PTV to cover 95% intrafractional motion was adequate in Group A but not in Group B.
在复发性头颈癌的挽救性立体定向消融放疗（SABR）期间，保持固定以尽量减少脊柱运动非常重要。本研究旨在比较两种固定方法之间的分次内运动。
利用图像引导的脊柱跟踪系统，获取了41例接受射波刀SABR治疗患者的9094条记录进行回顾性比较。21例患者使用热塑性面罩和头枕固定（A组），另外20例患者使用热塑性面罩和头枕并结合真空袋来支撑头颈部区域（B组）。比较两组在X轴（上下）、Y轴（左右）、Z轴（前后）方向的分次内运动、三维矢量、翻滚、俯仰和偏航。评估计划靶体积（PTV）覆盖95%分次内运动的边界。
A组在X轴、Y轴和三维矢量的平移运动明显小于B组。A组在翻滚和偏航方向的旋转误差也明显小于B组；相反，A组在俯仰方向的旋转误差较大。为覆盖95%的分次内运动，A组在X、Y和Z轴分别需要0.96、1.55和1.51mm的边界，B组分别需要1.06、2.86和1.34mm。
在大多数轴向上，热塑性面罩和带真空袋的头枕固定方法并不比不带真空袋的固定方法提供更好的固定效果。A组将2mm作为PTV覆盖95%分次内运动的边界在临床上是合适的，但B组不合适。
