补偿角度算法纠正放射治疗摆位旋转误差

Using compensate angles to correct rotation set-up errors in radiotherapy

目的:阐述一种在未配备六维治疗床的直线加速器上,使用旋转误差补偿角度消除患者旋转误差的方法。方法:使用锥形束CT(CBCT)获得患者每次六维摆位误差,在刚体假设下,根据摆位误差定义加速器坐标系和患者坐标系的变换矩阵。使用2个独立矢量描述加速器机架角、治疗床转角和准直器转角3个变量,对这2个矢量作坐标变换后,即可得到加速器旋转误差补偿角度。结果:使用加速器旋转误差补偿角度,能完全纠正治疗过程中的摆位旋转误差,纠正旋转误差耗时少,可以加入图像引导放射治疗(IGRT)的日常操作流程中。结论:用旋转误差补偿角度替代六维治疗床,纠正摆位旋转误差的方法简单可行,可以使未配备六维治疗床的加速器具备纠正摆位旋转误差的能力。

Objective： The purpose of this paper is to introduce a method of using compensate angles to eliminate rotation set-up errors without six-degree of freedom couch. Methods： To detect six-degree of freedom set-up errors, cone-beam computed tomography （CBCT） scans were acquired. These set-up errors were defined as a matrix to transform from accelerator coordinate system to patient coordinate system. Two independent vectors were defined to describe angles of gantry, collimator and couch in accelerator machine. Transformation of vectors were determined by transformation matrix and re-calculated back to the machine angles. Results： It was found that compensate angles can fully corrected the rotation angles in set-up with limited time consuming. It is feasible to implement compensate angles in routinely radiation procedure. Conclusion： With this method, it is possible to implement the complete corrections of set-up errors in radiotherapy without six-degree of freedom couch and it is convenient in operation as well.