Dual-energy X-ray imaging: benefits and limits

Abstract

Both in radiographic and tomographic mode, conventional X-ray imaging provides information about the examined object which is not sufficient to characterize it precisely. Dual-energy X-ray technique, which consists in combining two radiographs acquired at two distinct energies, allows to obtain both density and atomic number, thus to provide information about material composition, or at least to improve image contrast. Available systems usually perform energetic separation at source level, but separation at detector level is also possible for linear detectors, especially those devoted to translating objects control. Dual-energy equations can be easily written and solved for monochromatic energy spectra and perfect detectors, but become complex when considering realistic spectra, detector sensitivity, and system non-linearity. A decomposition into material basis, using experimental dual-material calibration, allows to solve an approximated system, while getting free of beam hardening and other disturbances. More generally, we analyze the various problems to be solved before benefiting from dual-energy approach, and propose available solutions. We evaluate influence of noise on results accuracy, that strongly influences materials distinguishability. We review the aspects to optimize when considering a specific industrial problem: choice of energy spectra, of materials basis, method design. Numerical simulation is an efficient tool for that optimal system design. Various industrial applications will be considered.

Segmentation of X‐ray computed tomography images of porous materials: A crucial step for characterization and quantitative analysis of pore structures

“…These problems can be alleviated to a certain extent through application of metal filters, careful detector calibration and sample centering, but not completely avoided. Application of wedge calibration and dual energy scans [Coleman and Sinclair, 1985;Rebuffel and Dinten, 2007] also alleviate beam hardening effects, but these techniques are rarely implemented in standard scanning procedures [Ketcham and Carlson, 2001].…”

Sharpening filter for false color imaging of dual-energy X-ray scans

“…Dualenergy X-ray imaging brings us benefits in the form of depth resolution enhancement, because of slightly different attenuation characteristics which are depending on photons energy. In this section data acquisition from detectors and creation of raw images is discussed, see [11]. The X-ray tube emits N 0 photons, but only N passes through the scanned object and reaches the detector.…”

Surface Extraction from Multi-Material Components for Metrology using Dual Energy CT

“…Concerning data acquisition in DECT there are two different techniques: the dual exposure / dual source and the dual (layer) detector technique [19]. Using the dual exposure / dual source technique a specimen is measured twice using different X-Ray energies.…”

“…A modified detector consisting of two separate layers generates two penetration images: the front layer detects low energy photons and the back layer high energy photons. The disadvantage of this method is that the energy separation of these detectors is rather poor [19]. An application area of this technique is baggage control systems for airport security [7].…”