Cunningham I A, Fenster A
Med Phys. 1987 Jul-Aug;14(4):533-7. doi: 10.1118/1.596064.
In this paper we describe a technique for determining the modulation transfer function (MTF) of an imaging system from an experimentally obtained edge profile. The technique includes an exact correction for the frequency passband of the finite-element differentiation required to obtain the line spread function from the edge spread function. This correction has been ignored by investigators in the past and is required whenever finite-element differentiation is used rather than analytic differentiation of a model fitted to the edge response data. The magnitude of the MTF correction is approximately 11% at f = fc/2 and approximately 57% at f = fc, where fc = fs/2 is the maximum frequency reproducible without aliasing with a sampling rate of fs. The correction is performed in the spatial frequency domain by multiplying the uncorrected MTF by 1/sinc (pi f/2fc). A computer simulation is presented to demonstrate the effect and the correction procedure. An experimental MTF of an x-ray image intensifier system obtained using this technique is found to be consistent with an MTF obtained using a bar pattern test phantom.
在本文中，我们描述了一种从实验获得的边缘轮廓确定成像系统调制传递函数（MTF）的技术。该技术包括对从边缘扩展函数获得线扩展函数所需的有限元微分的频率通带进行精确校正。过去研究人员忽略了这种校正，并且每当使用有限元微分而不是对拟合边缘响应数据的模型进行解析微分时都需要进行这种校正。MTF校正的幅度在f = fc/2时约为11%，在f = fc时约为57%，其中fc = fs/2是在采样率为fs时无混叠可再现的最大频率。该校正在空间频域中通过将未校正的MTF乘以1/sinc(πf/2fc)来执行。给出了一个计算机模拟以演示这种效果和校正过程。使用该技术获得的X射线图像增强器系统的实验MTF被发现与使用条形图案测试体模获得的MTF一致。
