Abstract：
OBJECTIVE: The main objective of this study was to assess inter- and intrafraction errors for two patient immobilisation devices in the context of lung stereotactic body radiation therapy: a vacuum cushion and a simple arm support.
METHODS: Twenty patients who were treated with lung stereotactic body radiation therapy in supine position with arms above their head were included in the study. Ten patients were setup in a vacuum cushion (Bluebag™, Elekta) and ten other patients with a simple arm support (Posirest™, Civco). A pretreatment four-dimensional cone-beam computed tomography and a post-treatment three-dimensional cone-beam computed tomography were acquired to compare positioning and immobilisation accuracy. Based on a rigid registration with the planning computed tomography on the spine at the target level, translational and rotational errors were reported.
RESULTS: The median number of fractions per treatment was 5 (range: 3-10). Mean interfraction errors based on 112 four-dimensional cone-beam computed tomographies were similar for both setups with deviations less than or equal to 1.3mm in lateral and vertical direction and 1.2° in roll and yaw. For longitudinal translational errors, mean interfraction errors were 0.7mm with vacuum cushion and -3.9mm with arm support. Based on 111 three-dimensional cone-beam computed tomographies, mean lateral, longitudinal and vertical intrafraction errors were -0.1mm, -0.2mm and 0.0mm respectively (SD: 1.0, 1.2 and 1.0mm respectively) for the patients setup with vacuum cushion, and mean vertical, longitudinal and lateral intrafraction errors were -0.3mm, -0.7mm and 0.1mm respectively (SD: 2.3, 1.8 and 1.4mm respectively) for the patients setup with arm support. Intrafraction errors means were not statistically different between both positions but standard deviations were statistically larger with arm support.
CONCLUSIONS: The results of our study showed similar inter and intrafraction mean deviations between both positioning but a large variability in intrafraction observed with arm support suggested a more accurate immobilization with vacuum cushion.
METHODS: Twenty patients who were treated with lung stereotactic body radiation therapy in supine position with arms above their head were included in the study. Ten patients were setup in a vacuum cushion (Bluebag™, Elekta) and ten other patients with a simple arm support (Posirest™, Civco). A pretreatment four-dimensional cone-beam computed tomography and a post-treatment three-dimensional cone-beam computed tomography were acquired to compare positioning and immobilisation accuracy. Based on a rigid registration with the planning computed tomography on the spine at the target level, translational and rotational errors were reported.
RESULTS: The median number of fractions per treatment was 5 (range: 3-10). Mean interfraction errors based on 112 four-dimensional cone-beam computed tomographies were similar for both setups with deviations less than or equal to 1.3mm in lateral and vertical direction and 1.2° in roll and yaw. For longitudinal translational errors, mean interfraction errors were 0.7mm with vacuum cushion and -3.9mm with arm support. Based on 111 three-dimensional cone-beam computed tomographies, mean lateral, longitudinal and vertical intrafraction errors were -0.1mm, -0.2mm and 0.0mm respectively (SD: 1.0, 1.2 and 1.0mm respectively) for the patients setup with vacuum cushion, and mean vertical, longitudinal and lateral intrafraction errors were -0.3mm, -0.7mm and 0.1mm respectively (SD: 2.3, 1.8 and 1.4mm respectively) for the patients setup with arm support. Intrafraction errors means were not statistically different between both positions but standard deviations were statistically larger with arm support.
CONCLUSIONS: The results of our study showed similar inter and intrafraction mean deviations between both positioning but a large variability in intrafraction observed with arm support suggested a more accurate immobilization with vacuum cushion.
摘要：
目的：本研究的主要目的是评估两种患者固定装置在肺立体定向身体放射治疗中的介入和介入误差：真空垫和简单的手臂支撑。
方法：本研究纳入了20例患者，这些患者均接受仰卧位的肺部立体定向放射治疗，手臂高于头部。十名患者被安置在真空垫中(Bluebag™，Elekta）和其他十名患者使用简单的手臂支撑（Posirest™，Civco）。获得了预处理的四维锥形束计算机断层扫描和治疗后的三维锥形束计算机断层扫描，以比较定位和固定的准确性。基于与目标水平脊柱上的计划计算机断层扫描的刚性配准，报告了平移和旋转误差。
结果：每次治疗的分数中位数为5（范围：3-10）。基于112个四维锥形束计算机断层摄影的平均分数误差对于两种设置都相似，在横向和垂直方向上的偏差小于或等于1.3mm，在滚动和偏航方向上的偏差为1.2°。对于纵向平移误差，真空垫的平均分数误差为0.7mm，手臂支撑的平均分数误差为-3.9mm。基于111种三维锥束计算机断层摄影，平均横向，纵向和垂直内交误差为-0.1mm，-分别为0.2mm和0.0mm（分别为SD：1.0、1.2和1.0mm），用于设置真空垫的患者，意思是垂直的，纵向和横向内交误差为-0.3mm，-分别为0.7mm和0.1mm（分别为SD：2.3、1.8和1.4mm），用于设置手臂支撑的患者。两个位置之间的内交误差平均值在统计学上没有差异，但是手臂支撑的标准偏差在统计学上较大。
结论：我们的研究结果表明，两种定位之间的帧内和帧内平均偏差相似，但在手臂支撑下观察到的帧内平均偏差很大，这表明使用真空垫可以更准确地固定。
方法：本研究纳入了20例患者，这些患者均接受仰卧位的肺部立体定向放射治疗，手臂高于头部。十名患者被安置在真空垫中(Bluebag™，Elekta）和其他十名患者使用简单的手臂支撑（Posirest™，Civco）。获得了预处理的四维锥形束计算机断层扫描和治疗后的三维锥形束计算机断层扫描，以比较定位和固定的准确性。基于与目标水平脊柱上的计划计算机断层扫描的刚性配准，报告了平移和旋转误差。
结果：每次治疗的分数中位数为5（范围：3-10）。基于112个四维锥形束计算机断层摄影的平均分数误差对于两种设置都相似，在横向和垂直方向上的偏差小于或等于1.3mm，在滚动和偏航方向上的偏差为1.2°。对于纵向平移误差，真空垫的平均分数误差为0.7mm，手臂支撑的平均分数误差为-3.9mm。基于111种三维锥束计算机断层摄影，平均横向，纵向和垂直内交误差为-0.1mm，-分别为0.2mm和0.0mm（分别为SD：1.0、1.2和1.0mm），用于设置真空垫的患者，意思是垂直的，纵向和横向内交误差为-0.3mm，-分别为0.7mm和0.1mm（分别为SD：2.3、1.8和1.4mm），用于设置手臂支撑的患者。两个位置之间的内交误差平均值在统计学上没有差异，但是手臂支撑的标准偏差在统计学上较大。
结论：我们的研究结果表明，两种定位之间的帧内和帧内平均偏差相似，但在手臂支撑下观察到的帧内平均偏差很大，这表明使用真空垫可以更准确地固定。
