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为有效实现数字射线扫描成像检测系统性能的定量分析评价,据此进行检测工艺参数的优化,对数字射线扫描成像检测系统调制传递函数(Modulation transfer function,MTF)进行了测试分析。采用刀口工具、双线型像质计、分辨率测试卡,对系统在不同焦点大小、放大倍数、运动方向的检测情况,分别进行了MTF的测试并进行了比较。结果表明,双线型像质计与分辨率测试卡的测试结果基本一致,但双线型像质计更便于对比度的定量计算;双线型像质计的对比度传递函数近似符合二次曲线,经转换得到的调制传递函数值高于刀口法的测试值,刀口法计算数值偏低的原因在于运动不平稳所带来的不利影响。分析表明,数字射线扫描成像系统性能受到多个因素的共同影响,MTF测试结果可较全面地对影响因素进行定量评价,可用于确定最佳的检测参数或找出等价的参数组合。
In order to effectively evaluate the performance of the digital radiography scanning system, the optimization of the testing parameters was carried out. The modulation transfer function (MTF) of the digital radiography scanning system was tested and analyzed. Using the tool edge, two-line image quality meter, resolution test card, the system in different focus size, magnification, the direction of motion detection, respectively, were tested MTF and compared. The results show that the test results of the two-line image quality meter and the resolution test card are basically the same, but the two-line type image quality meter is more convenient for the quantitative calculation of the contrast ratio. The contrast transfer function of the two-line type image quality meter closely conforms to the quadratic curve, The converted modulation transfer function value is higher than the blade edge test value. The reason for the low numerical calculation by the blade edge method lies in the unfavorable influence brought by unsteady movement. The analysis shows that the performance of digital ray scanning imaging system is affected by many factors. The MTF test results can be used to quantitatively evaluate the influencing factors and can be used to determine the best detection parameters or find the equivalent parameter combinations.