【摘要】 目的:自制运动体模,探讨呼吸运动对靶区三维重建的影响。方法:用VEXTA步进电机、YT-H200B型步进电机驱动器、导轮、有机玻璃球、低密度度泡沫等设计能模拟肿瘤随呼吸运动的体模;取不同螺距、层厚和运动周期组成10个不同的扫描序列在GELightSpeed16CT上扫描,然后在GEAdvantageSim6.0上采用体绘制技术(volumerendering)对所获得CT图像进行三维重建,用三维工具软件测量不同扫描条件下各靶体积大小,计算动态与静态扫描靶区重建体积的相对偏差。结果:静态体模同一靶区在层厚与螺距不同时,扫描后三维重建的靶区外观无明显可见变化,重建靶区的体积差异可忽略;在不同运动状态下扫描,同一靶区重建图像的外形差异明显,重建靶体积的相对偏差最大近90%;同一运动状态下,各靶区重建体积变化随靶而异;外形较小的靶区重建体积相对偏差变化范围为-39.8%～89.5%,外形较大的靶区重建体积相对偏差变化范围是-18.4%～20.5%。结论:呼吸运动对靶区重建的响影极大,三维放疗计划设计所依赖的CT图像,必须是肿瘤靶区处于相对静止状态下扫描的图像,否则,适形射野和剂量体积直方图将严重失真。更多还原

【Abstract】 Objective:To develop a phantom which can simulate human respiration and study the respiratory effects on three-dimensional reconstruction of the tumor targets.Methods:The phantom which can simulate the respiration was made by VEXTA step motor,YT-H200B motor,small ball of polymethyl methacrylate and potatos.Ten series with different scan pitches,slices,periods and initial phases were set and the phantom was scanned by GE LightSpeed 16 CT scanner.The three-dimensional reconstruction of CT images of the phantom were completed by adopting the volume rendering technology of GE AdvantageSim 6.0 system,and the volumes of each targets of different series were measured by the three-dimensional measuring tools.Thus,the relative deviations of reconstruction volumes between move targets and the stationary ones were calculated.Results:There is no obvious difference between the three-dimensional reconstructions of stationary targets which were scanned with different pitches and slices.There are great differences between the three-dimensional reconstructions of move and stationary targets,and the maximal relative deviation of volume is nearly 90% for the same target scanned with different pitches,slices and periods.The relative deviation of reconstruction volume is variable amonge the different targets,it is about-39.8%～89.5% for the smaller targets and-18.4%～20.5% for the larger targets.Conclusion:The respiration has great effects on the three-dimensional reconstruction of the tumor targets.The CT images adopted in three-dimensional TPS must be the stationary images.Otherwise,the conformal radiation fields will be distorted greatly and the DVH will be false.更多还原