三维适形放疗计划系统需要根据射束的不同类型和方向，在照射位置和区域上覆盖目标（肿瘤）区域的同时避免周围正常组织的过量照射，确保照射精度。发展了一种射束建模方法：①通过推导坐标系转换矩阵，将病人影像坐标系统下的三维病人模型转换到射束坐标系下；②计算照射目标中心点坐标并以此确定照射距离和射束源位置；③根据照射目标在等中心平面上的投影确定照射区域大小。应用该方法，实现了具有三维可视效果和友好交互性的射束模块。采用美国医学物理协会55号报告（AAPM 55）中基准测例和临床病人影像数据，与某商业适形放疗计划系统的射束模块进行测试比较，验证了本方法的有效性和正确性。%To insure the accuracy of irradiation ,the three‐dimensional conformal radiation therapy (3DCRT ) treatment planning system (T PS ) should ,based on the types and orientations of the beam ,automatically calculate the source position and the field size of the irradiation beam to cover the target (tumor) volume w hile avoiding excessive irradiation of the surrounding tissues . A beam modeling method was developed :first ,based on the derived matrix of coordinate system transformation ,the 3D patient model is tranfered from the patient coordinate system to the beam coordinate system ;then , the iso‐center coordinate of the target is caculated , from w hich the coordinate of the beam source is derived ;finally , the target volume is projected onto the iso‐center plane to identify the field size of the irradiation beam .By implementing of this method ,the beam modeling module was developed with features of 3D visualization and a friendly user interface .The accuracy and efficiency of this module was verified based on the benchmark cases of the AAPM report 55 and the clinical patient image data by testing and comparing it with the beam modeling module of a commercial 3DCRT T PS .
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