Dumas J-L, Fawzi M, Masset H, Losa S, Dal R, Pierrat N, de Marzi L
Service de physique médicale, département de radiothérapie, Institut Curie, 26 rue d'ULM, site de Paris 75005 Paris, France.
Service de physique médicale, département de radiothérapie, Institut Curie, 26 rue d'ULM, site de Paris 75005 Paris, France.
Cancer Radiother. 2020 Jun;24(3):199-205. doi: 10.1016/j.canrad.2020.01.005. Epub 2020 Mar 9.
A high level of accuracy while positioning the patient is mandatory for frameless stereotactic radiotherapy (SRT), as large doses in multiple fractions can be delivered near organs at risk. The objective of this study is to propose an end-to-end quality assurance method to verify that submillimetre alignment can be achieved with stereotactic conventional linacs.
We used a TrueBeam® linear accelerator equipped with a 6DOF robotic couch. The "ISO Cube" phantom was used with a homemade stand designed to generate known translational and rotational offsets. A reference CT scan was performed with straight alignment of the phantom. The procedure introduced 1.6° angular offset for the couch pitch and roll, at various gantry angles. The couch base was also moved between 0° and 270°. We compared the results with the daily machine performance check tests (MPC, Varian).
The mean isocentre size, MV and kV imager offsets were found to agree to within 0.1mm, 0.1mm and 0.3mm respectively, and were in close agreement between the methods. For a total four months data collection period, the mean deviation between requested and measured 6DOF couch shifts was 0.6mm and 0.2°. Errors on field size were smaller than 1mm for 97.7% of the 324 data points.
Results demonstrate that the linac equipped with a 6DOF robotic positioner and CBCT imaging satisfies requirements for SRT. Our methodology, based on a modified Winston-Lutz quality control, allowed us to quantitatively assess end-to-end accuracy of a linac in order to safely deliver SRT.
在无框架立体定向放射治疗（SRT）中，患者定位时的高精度至关重要，因为多分割的大剂量辐射可能会作用于危及器官附近。本研究的目的是提出一种端到端的质量保证方法，以验证使用立体定向传统直线加速器能否实现亚毫米级的对准。
我们使用了一台配备六自由度（6DOF）机器人治疗床的TrueBeam®直线加速器。“ISO Cube”模体与一个自制支架配合使用，该支架旨在产生已知的平移和旋转偏移。在模体直线对准的情况下进行了一次参考CT扫描。在不同的机架角度下，为治疗床的俯仰和横滚引入了1.6°的角度偏移。治疗床基座也在0°至270°之间移动。我们将结果与每日机器性能检查测试（MPC，瓦里安公司）进行了比较。
发现平均等中心尺寸、MV和kV成像仪偏移分别在0.1mm、0.1mm和0.3mm以内一致，并且两种方法之间的结果非常吻合。在总共四个月的数据收集期内，请求的和测量到的6DOF治疗床位移之间的平均偏差为0.6mm和0.2°。在324个数据点中，97.7%的野尺寸误差小于1mm。
结果表明，配备六自由度机器人定位器和CBCT成像的直线加速器满足SRT的要求。我们基于改进的温斯顿-卢茨质量控制的方法，使我们能够定量评估直线加速器的端到端精度，以便安全地进行SRT治疗。
