A dual-layer direct/indirect flat panel detector for improved material decomposition: first studies of the indirect layer.

In medical imaging, material decomposition and lesion differentiation are essential for the early detection of many severe and deadly diseases. While standard flat panel imagers are capable of providing high-resolution images, they lack the ability to differentiate between X-ray energies and, therefore, soft and hard tissues. Detection of multiple X-ray energies by dual-shot, photon counting, or dual-layer detectors provides a route for differentiation of these tissues based on the spectrum observed; multiple images may be generated based on the energies, allowing for subtraction and a more detailed image of tissues and calcifications. To improve the resolution, dose level, and motion artifacts of these imagers, we propose a new dual-layer detector consisting of a direct conversion amorphous selenium top layer, followed by an indirect conversion scintillator/amorphous selenium bottom layer. In this work, we present the first steps towards building this detector by characterizing the performance of the bottom indirect flat panel. We show that the blocking layer chosen, though unoptimized, performs adequately up to 50 V/um and have fabricated the detector, which will be evaluated for detective quantum efficiency and modulation transfer function.