2x2 Oversampling in Digital Radiography Imaging for CsI-based Scintillator Detectors

In order to efficiently conduct the anti-aliasing filtering in digital radiography imaging, the oversampling scheme using an oversampling detector, in which the sampling frequency is higher than that of the desired detector, is considered in this paper. Instead of using difficult analog anti-aliasing filters, digital anti-aliasing filters are applied to the oversampled data and then their downsampling enables acquiring the desired x-ray images. Supposing an ideal anti-aliasing filtering, the detective quantum efficiency (DQE) performance of the desired detector can be close to that of the oversampling detector since the overlap of the adjacent noise aliases can be minimized while maintaining the frequency amplitude response for the fundamental frequency range. In this paper, a 2 x 2 oversampling is conducted for the desired pixel pitch of 152 mu m/pixel and various filters are tested for anti-aliasing filtering. It is shown that securing an enough transition band is important to avoid the ringing artifacts even though the anti-aliasing performance deteriorates due to the wide transition band. From an experiment using a CsI(Tl)-based detector, the aliasing artifact problem is alleviated and a DQE improvement of 0.1 is achieved at 2.5 lp/mm from the oversampling radiography imaging over the binning scheme.