中文摘要：

用MonteCarlo模拟、三维水箱和MatriXX测量的方法，获取机架角在0°-80°和280°-360°（0°）内的6MVx射线的离轴比曲线，利用三种曲线分析MatriXX二维电离室阵列的角度响应。结果表明，在0°～60°和300°-360°（0°），三种方法得到的离轴比曲线一致性较好；在70°-80°和280°-290°，Monte Carlo计算和MatriXX测量的曲线及平面中心点剂量均存在明显差异。研究结果为多机架角度照射合成验证调强放疗计划的剂量分布提供依据。

英文摘要：

With the gantry angles of 0°-80° and 280°-360°（0°）, the offaxis distance （OAR） profiles curves of 6 MV X-ray were obtained by Monte Carlo simulation, 3-D water phantom measurement and MatriXX measurement. Comparing the three types of curves, we analyzed the angular dependence of MatriXX 2-D chamber array. The results revealed that the three types of curves agreed well with the gantry angles of 0°-60°and 300°-360°（0°）. Curves and centre point dose on plane from Monte Carlo simulation differed obviously from those of MatriX.X measurement in gantry angles of 70°-90° and 270°-290°. It is possible to verify the dose distribution of intensity modulated radiation therapy （IMRT） plan using the Multi-Gantry-Angle Composite （MGAC）.