Modulation transfer function for radiographic system

Modulation transfer function (MTF) is a mathematical tool for assessing and evaluation of the performance of an imaging system. To evaluate the performance of X-ray and gamma radiography systems, a simple method was used for the measurement of resolution properties of these systems. Line spread function was used as the measurement method to determine modulation transfer function. Highly absorbing materials were used to study the resolution properties of the imaging systems. Various X-ray films were exposed at different kV(s). The radiographs were scanned by a digital micro-densitometer. The line spread functions for diffraction film screen combinations were measured. The Fourier transform of the averaged line spread functions provided the modulation transfer function. Curve fitting was carried out applying Gaussian and adjacent averaging methods. Modulation transfer functions of different X-ray films and screen combinations used in industrial radiography were measured to determined the resolution characteristics. This study has proved that MTF is a better tool for assessing the resolution characteristics as compared to image quality indicators. (author)