Convex Combination of Images from Dual-Layer Detectors for High Detective Quantum Efficiencies.

Abstract

In this paper, a novel dual-layer detector is considered to acquire X-ray images of high signal-to-noise ratio (SNR) as well as detective quantum efficiency (DQE) especially for high voltages of X-ray tubes. To achieve a uniform alignment property, the upper and lower detector layers are stacked with an aligning procedure while minimizing the layer distance. A convex combination of the images acquired from the layers is optimized with respect to the combination coefficient. For the optimization and an alignment analysis based on Monte Carlo simulations, parametric modeling for the detector is also conducted. It is shown that for a given spatial frequency, the optimized DQE of the convex combination image (CCI) is the summation of the DQE values of the upper and lower layers. For extensive experiments, several types of the aligned dual-layer detector (ADD) are practically constructed to acquire CCI. The experimental results under a beam quality of RQA9 showed that ADD could efficiently increase the DQE value from 50% to more than 75% at zero frequency. ADD can be used for increasing DQE as well as conventional spectral detector applications. CCI acquired from ADD can have significantly higher DQE values compared to the single-layer cases.