DIGITAL RADIOLOGY USING ACTIVE-MATRIX READOUT OF AMORPHOUS SELENIUM -CONSTRUCTION AND EVALUATION OF A PROTOTYPE REAL-TIME DETECTOR

The goal of the present work is to develop a large area, flat-panel so lid-state detector for both digital radiography and fluoroscopy. The p roposed detector employs a photoconductive layer of amorphous selenium (a-Se) to convert x rays into charge. The charge image formed by the a-Se layer is electronically read out in situ using a two dimensional array of thin film transistors (TFTs), or active matrix. Since the act ive matrix readout is capable of producing x-ray images in real-time, it can potentially be applied in both radiography and fluoroscopy. In this paper, the imaging performance of this concept is investigated us ing a prototype x-ray imaging detector. The designs for the active mat rix, the peripheral electronic circuits, and the image acquisition sys tem are described. Measurements of x-ray imaging properties of the pro totype detector, i.e., x-ray sensitivity, presampling modulation trans fer function (MTF), and noise power spectrum (NPS), were performed, an d from which the spatial frequency dependent detective quantum efficie ncy (DQE) of the prototype was derived. The experimental results are i n agreement with the results of our theoretical analysis. The factors affecting the imaging performance and methods of improvement in the fu ture are discussed. (C) 1997 American Association of Physicists in Med icine.