Comparison of setup accuracy of three different thermoplastic masks for the treatment of brain and head and neck tumors
Comparison of setup accuracy of three different thermoplastic masks for the treatment of brain and head and neck tumors
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DOI：
10.1016/s0167-8140(00)00280-2
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发表时间：
2001-02-01
影响因子：
5.7
通讯作者：
Grégoire, V
中科院分区：
文献类型：
--
作者：
Gilbeau, L;Octave-Prignot, M;Grégoire, V
目的：摆位精度是影响计划靶区（PTV）定义的重要因素。本研究的目的是比较三种不同的热塑性口罩用于固定脑或头颈部肿瘤患者的设置精度。材料和方法：30例脑或头颈部肿瘤患者连续分配到三种不同的热塑性口罩之一（Posifix（R））：具有三个固定点头罩（3个FP，10名患者），头和肩面罩，带4个固定点（4个FP，10名患者），具有5个固定点的头和肩面罩（5个FP，4个固定点加上头顶上的一个额外固定点，10名患者）。每周一次，在使用6 MV直线加速器（Elekta（R））的会话期间，针对模拟期间放置在头部、颈部和肩部水平的三个虚拟等中心点采集正交（前后和侧向）射野图像。使用PIPS pro软件比较射野图像和数字化模拟器片，并计算前后（A-P）、颅尾（C-C）和内外（M-L）方向的位移。从这些位移，2D或3D的错误也counted.Results：共获得915个射野图像，其中98%可以分析。对于整个人群，头部和颈部水平的总位移达到2.2 mm的标准差（SD）。系统和随机位移处于相同的数量级，并达到1.8 mm的SD。患者在肩关节水平的设置略差，C-C和M-L方向的总位移为2.8 mm（1 SD）。同样，系统和随机分量在2.4 mm（+/-SD）以下的数量级相同。对于头部和颈部的等中心点，三种面罩之间的设置偏差没有实质性差异。在肩部水平，使用3 FP面罩的设置再现性明显较差（P = 0.01）。对于2D随机误差，观察到2.3 mm的1 SD，而4和5 FP面罩分别为0.8和1.2 mm。最后，90%的头部和颈部3D总偏差低于4.5 mm。在肩部区域，90%的2D总偏差低于5.5 mm。结论：热塑性口罩提供了准确的患者固定。在肩部水平，当使用4或5个FP掩模时，设置变化减小。这些数据可用于评估PTV的边缘。(C)2001爱思唯尔科学爱尔兰有限公司保留所有权利。
Purpose: Setup accuracy is an important factor influencing the definition of the planning target volume (PTV). The purpose of this study was to compare the setup accuracy of three different thermoplastic masks used for immobilization of patients with brain or head and neck tumors.Materials and methods: Thirty patients with brain or head and neck tumors were consecutively assigned to one of three different thermoplastic masks (Posifix(R)): head mask with three fixation points (3 FP, ten patients), head and shoulder mask with four fixation points (4 FP, ten patients), head and shoulder mask with five fixation points (5 FP, four fixations plus an additional one on the top of head, ten patients). Once a week, during the session with a 6 MV linac (Elekta(R)), orthogonal (antero-posterior and lateral) portal images were acquired for three fictitious isocenters placed during the simulation at the level of the head, the neck and the shoulders. Portal images and digitized simulator films were compared using the PIPS pro software, and displacements in antero-posterior (A-P), cranio-caudal (C-C) and mediolateral (M-L) directions were calculated. From these displacements, 2D or 3D errors were also calculated.Results: A total of 915 portal images were obtained, of which 98% could be analyzed. For the whole population, total displacements reached a standard deviation (SD) of 2.2 mm at the level of the head and the neck. Systematic and random displacements were in the same order of magnitude and reached a SD of 1.8 mm. Patient setup was slightly worse at the shoulder level with a total displacement of 2.8 mm (1 SD) for both the C-C and the M-L directions. There again, the systematic and the random components were in the same order of magnitude below 2.4 mm (+/- SD). For isocenters in the head and in the neck, there was no substantial difference in the setup deviation between the three masks. The setup reproducibility was found to be significantly worse (P = 0.01) at the level of the shoulders with the 3 FP mask. For the 2D random error, 1 SD of 2.3 mm was observed compared to 0.8 and 1.2 mm for the 4 and 5 FP masks; respectively. Lastly, 90% of the 3D total deviations were below 4.5 mm for the head and the neck. In the shoulder region, 90% of the 2D total deviations were below 5.5 mm.Conclusion: Thermoplastic masks provide an accurate patient immobilization. At the shoulder level, setup variations are reduced when 4 or 5 FP masks are used. These data could be used for the assessment of margins for the PTV. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.