Abstract：
Background.The MTF has difficulties being determined (according to the provisions of the IEC standards) in the hospital setting due to the lack of resources.Purpose.The objective of this work is to propose a quantitative method for obtaining the point spread function (PSF) and the modulation transfer function (MTF) of a digital mammography system from an image of a bar pattern.Methods.The method is based on the measurement of the contrast transfer function (CTF) of the system over the image of the bar pattern. In addition, a theoretical model for thePSFis proposed, from which the theoreticalCTFof the system is obtained by means of convolution with a square wave (mathematical simulation of the bar pattern). Through an iterative process, the free parameters of thePSFmodel are varied until the experimentalCTFcoincides with the one calculated by convolution. Once thePSFof the system is obtained, we calculate theMTFby means of its Fourier transform. TheMTFcalculated from the modelPSFhave been compared with those calculated from an image of a 65μm diameter gold wire using an oversampling process.Results.TheCTFhas been calculated for three digital mammographic systems (DMS 1, DMS 2 and DMS 3), no differences of more than 5 % were found with the CTF obtained with the PSF model. The comparison of theMTFshows us the goodness of thePSFmodel.Conclusions.The proposed method for obtainingPSFandMTFis a simple and accessible method, which does not require a complex configuration or the use of phantoms that are difficult to access in the hospital world. In addition, it can be used to calculate other magnitudes of interest such as the normalized noise power spectrum (NNPS) and the detection quantum efficiency (DQE).
摘要：
背景：由于缺乏资源，在医院环境中（根据IEC标准的规定）很难确定MTF。
目的：这项工作的目的是提出一种定量方法，用于从条形图案的图像中获得数字乳房X线摄影系统的点扩散函数（PSF）和调制传递函数（MTF）。
方法：该方法基于在条形图案的图像上测量系统的对比度传递函数（CTF）。此外,提出了PSF的理论模型，通过与方波的卷积（条形图案的数学模拟），可以从中获得系统的理论CTF。通过一个迭代过程，PSF模型的自由参数变化，直到实验CTF与卷积计算得出的一致。一旦获得系统的PSF，我们通过傅里叶变换来计算MTF。已将从模型PSF计算的MTF与使用过采样过程从65μm直径的金线的图像计算的MTF进行了比较。
结果：已经计算了三个数字乳腺摄影系统（DMS1，DMS2和DMS3）的CTF，用PSF模型获得的CTF没有发现超过5%的差异。MTF的比较向我们展示了PSF模型的良好性。
结论：提出的获得PSF和MTF的方法是一种简单易用的方法，这不需要复杂的配置或使用难以在医院世界中访问的幻影。此外,它可用于计算其他感兴趣的量值,例如归一化噪声功率谱(NNPS)和检测量子效率(DQE)。
目的：这项工作的目的是提出一种定量方法，用于从条形图案的图像中获得数字乳房X线摄影系统的点扩散函数（PSF）和调制传递函数（MTF）。
方法：该方法基于在条形图案的图像上测量系统的对比度传递函数（CTF）。此外,提出了PSF的理论模型，通过与方波的卷积（条形图案的数学模拟），可以从中获得系统的理论CTF。通过一个迭代过程，PSF模型的自由参数变化，直到实验CTF与卷积计算得出的一致。一旦获得系统的PSF，我们通过傅里叶变换来计算MTF。已将从模型PSF计算的MTF与使用过采样过程从65μm直径的金线的图像计算的MTF进行了比较。
结果：已经计算了三个数字乳腺摄影系统（DMS1，DMS2和DMS3）的CTF，用PSF模型获得的CTF没有发现超过5%的差异。MTF的比较向我们展示了PSF模型的良好性。
结论：提出的获得PSF和MTF的方法是一种简单易用的方法，这不需要复杂的配置或使用难以在医院世界中访问的幻影。此外,它可用于计算其他感兴趣的量值,例如归一化噪声功率谱(NNPS)和检测量子效率(DQE)。
