Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Switzerland.
Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern, Switzerland.
Z Med Phys. 2014 May;24(2):112-22. doi: 10.1016/j.zemedi.2013.11.002. Epub 2014 Jan 10.
The range of patient setup errors in six dimensions detected in clinical routine for cranial as well as for extracranial treatments, were analyzed while performing linear accelerator based stereotactic treatments with frameless patient setup systems. Additionally, the need for re-verification of the patient setup for situations where couch rotations are involved was analyzed for patients treated in the cranial region.
A total of 2185 initial (i.e. after pre-positioning the patient with the infrared system but before image guidance) patient setup errors (1705 in the cranial and 480 in the extracranial region) obtained by using ExacTrac (BrainLAB AG, Feldkirchen, Germany) were analyzed. Additionally, the patient setup errors as a function of the couch rotation angle were obtained by analyzing 242 setup errors in the cranial region. Before the couch was rotated, the patient setup error was corrected at couch rotation angle 0° with the aid of image guidance and the six degrees of freedom (6DoF) couch. For both situations attainment rates for two different tolerances (tolerance A: ± 0.5mm, ± 0.5°; tolerance B: ± 1.0 mm, ± 1.0°) were calculated.
The mean (± one standard deviation) initial patient setup errors for the cranial cases were -0.24 ± 1.21°, -0.23 ± 0.91° and -0.03 ± 1.07° for the pitch, roll and couch rotation axes and 0.10 ± 1.17 mm, 0.10 ± 1.62 mm and 0.11 ± 1.29 mm for the lateral, longitudinal and vertical axes, respectively. Attainment rate (all six axes simultaneously) for tolerance A was 0.6% and 13.1% for tolerance B, respectively. For the extracranial cases the corresponding values were -0.21 ± 0.95°, -0.05 ± 1.08° and -0.14 ± 1.02° for the pitch, roll and couch rotation axes and 0.15 ± 1.77 mm, 0.62 ± 1.94 mm and -0.40 ± 2.15 mm for the lateral, longitudinal and vertical axes. Attainment rate (all six axes simultaneously) for tolerance A was 0.0% and 3.1% for tolerance B, respectively. After initial setup correction and rotation of the couch to treatment position a re-correction has to be performed in 77.4% of all cases to fulfill tolerance A and in 15.6% of all cases to fulfill tolerance B.
The analysis of the data shows that all six axes of a 6DoF couch are used extensively for patient setup in clinical routine. In order to fulfill high patient setup accuracies (e.g. for stereotactic treatments), a 6DoF couch is recommended. Moreover, re-verification of the patient setup after rotating the couch is required in clinical routine.
在使用无框架患者定位系统进行基于线性加速器的立体定向治疗时，分析在颅部和颅外治疗中临床常规中检测到的六个维度的患者定位误差范围。此外，还分析了在涉及治疗床旋转的情况下，对颅部患者进行重新验证患者定位的必要性。
共分析了 2185 例初始（即使用红外系统预定位患者后但在图像引导之前）患者定位误差（颅部 1705 例，颅外 480 例），使用 ExacTrac（德国 Feldkirchen 的 BrainLAB AG）获得。此外，通过分析颅部的 242 个定位误差，获得了治疗床旋转角度与患者定位误差之间的关系。在旋转治疗床之前，借助图像引导和六自由度（6DoF）治疗床，在治疗床旋转角度为 0°时对患者定位误差进行校正。对于这两种情况，均计算了两个不同容差（容差 A：±0.5mm，±0.5°；容差 B：±1.0mm，±1.0°）的达成率。
颅部病例的初始患者定位误差平均值（±一个标准差）分别为 -0.24 ± 1.21°、-0.23 ± 0.91°和-0.03 ± 1.07°，用于俯仰、滚动和治疗床旋转轴，0.10 ± 1.17mm、0.10 ± 1.62mm 和 0.11 ± 1.29mm，用于侧位、纵向和垂直轴。容差 A 的达成率（所有六个轴同时）为 0.6%，容差 B 的达成率为 13.1%。对于颅外病例，相应的值分别为-0.21 ± 0.95°、-0.05 ± 1.08°和-0.14 ± 1.02°，用于俯仰、滚动和治疗床旋转轴，0.15 ± 1.77mm、0.62 ± 1.94mm 和-0.40 ± 2.15mm，用于侧位、纵向和垂直轴。容差 A 的达成率（所有六个轴同时）为 0.0%，容差 B 的达成率为 3.1%。初始定位校正和治疗床旋转到治疗位置后，为满足容差 A，所有病例中需要重新校正的比例为 77.4%，为满足容差 B，所有病例中需要重新校正的比例为 15.6%。
数据分析表明，6DoF 治疗床的所有六个轴在临床常规中广泛用于患者定位。为了达到高精度的患者定位（例如，用于立体定向治疗），建议使用 6DoF 治疗床。此外，在临床常规中需要在旋转治疗床后重新验证患者的定位。
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