Analysis of absorption signal and noise in thin phosphor detectors for high-energy transmission radiography

Abstract

We investigated the detective quantum efficiency (DQE) of thin gadolinium oxysulfide phosphor-based flat-panel detectors (FPDs) using cascaded-systems analysis and Monte Carlo (MC) simulations for applications in megavoltage (MV) x-ray industrial imaging. We decomposed the DQE formula into (dose-independent) upper-limit DQE and (dose-dependent) DQE-reduction factors. We obtained the absorbed energy distributions (AEDs) for various x-ray detector designs and photon energies using MC simulations and applied the AED analysis to the DQE formula. The investigations examined include the x-ray-detector-only DQE and the effect of the coupling efficiency between the x-ray detector and readout panel, including electronic noise, on the upper-limit DQE. This study confirms that the design of the metal build-up layer on the phosphor is effective for MV imaging and emphasizes the importance of designing the readout panel to maintain the upper-limit DQE. We expect the proposed DQE analysis to be suitable for designing and evaluating FPDs for high-energy nondestructive x-ray testing.