Development of 14' x 8.5' active matrix flat-panel digital x-ray detector system and imaging performance

Digital radiographic systems based on solid-state detectors, commonly referred to as flat-panel detectors, are gaining popularity in clinical practice. Large area, flat panel solid state detectors are being investigated for digital radiography. The purpose of this work was to evaluate the active matrix flat panel digital x-ray detectors in terms or their modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). In this paper, development and evaluation of a selenium-based flat-panel digital x-ray detector are described. The prototype detector has a pixel pitch of 139 μ m and a total active imaging area of 14 x 8.5 inch2 giving a total 3.9 million pixels. This detector include a x-ray imaging layer of amorphous selenium as a photoconductor which is evaporated in vacuum state on a TFT flat panel, to make signals in proportion to incident x-ray. The film thickness was about 500 μ m. To evaluate the imaging performance of the digital radiography (DR) system developed in our group, sensitivity, linearity, the modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) of detector was measured. The measured sensitivity was 4.16 x 106 ehp/pixel·mR at the bias field of 10 V/ μ m: The beam condition was 41.9 KeV. Measured MTF at 2.5 lp/mm was 52%, and the DQE at 1.5 lp/mm was 75%. And the excellent linearity was showed where the coefficient of determination (r2) is 0.9693