On the performance of a stacked dual-layer flat-panel detector

In radiography, dual-layer detectors are commonly used to separate objects such as bones and tissues. Additionally, the use of dual-layer detectors allows for X-ray images with improved detection quantum efficiency (DQE) performance. In this paper, we observe the DQE performance of a dual-layer detector, in which two flat-panel detector layers are stacked with a minimal distance between the layers. To design an aligned dual-layer detector (ADD), a subpixel registration based on an amplitude response is employed between the images acquired from the upper and lower layers, and the lower image is translated based on the Fourier shift theorem. The performance of ADD is evaluated by observing a convex combination of the upper and lower images in terms of the modulation transfer function (MTF), noise power spectrum, and DQE. We also observe the contrast performance by using a contrast-detail phantom of CDRAD. ADD can obtain a better performance than that of the single upper detector layer especially at relatively high x-ray tube voltages. For example, under the RQA 9 condition, ADD can achieve a DQE of 75:0% compared to 56:1% for a single layer detector at zero frequency. Additionally, the problem of non-uniform MTF and DQE across the pixels of the entire detector and the artifact problem caused by the antiscatter grid are also discussed.