A New Simplified Practical Analysis for Measuring the Presampled MTF Using a “Virtual Slit” Image from an Edge Image

We are proposing a new simplified practical method for measuring the presampled MTF of digital radiographic systems using a “virtual slit” image from an edge image. The basic concept of our approach is the combination of the edge and slit methods. This method differs from previous methods in that it derives the Line Spread Function (LSF) without numeric differentiation of the Edge Spread Function (ESF). The accuracy and uncertainty of the new method was investigated using simulated images (whose true MTFs are known) and a clinical indirect flat panel detector (FPD). In the simulations, the new method had a higher accuracy than the IEC method. In the clinical system, both the MTFs of the new and the IEC methods are in good agreement for frequencies up to the Nyquist frequency limit (within 0.0028). The standard deviation (SD) of the MTF using the new method was comparable with that of the IEC method. The results showed that our method has a small influence on the phase error according to the edge angle and the noise reduction effect. In our method, we can calculate the LSF from a “virtual slit” image and obtain a precise presampled MTF much more easily than in previous methods.