Imaging characteristics of a high resolution computed radiography system

The objective of this study is to characterize the imaging performance of a high resolution computed radiography (CR) system. The finest pixel pitch of the system is 43.75 mu m. The Modulation Transfer Function (MTF) of the CR system was measured on both scan and subscan directions. The Noise Power Spectrum (NPS) and Detective Quantum Efficiency (DQE) were also determined under different conditions. The MTF results on subscan direction showed 90%, 45% and 10% modulation at 1, 3, and 7 lp/mm resolutions, respectively; on scan direction the MTF values are slightly lower. The DQE value of this CR system at low frequency under 26 kVP is as high as 45%. As a comparison, these measurements were repeated with a CCD based system (48 mu m pixel pitch) using the same x-ray source. The unique features of this CR system, such as its high limiting spatial resolution and detective quantum efficiency, make it attractive in applications such as mammography.