Noise analysis of grating-based x-ray differential phase contrast imaging

Abstract

The sensitivity of x-ray radiographic images, meaning the minimal detectable change in the thickness or in the index of refraction of a sample, is directly related to the uncertainty of the measurement method. In the following work, we report on the recent development of quantitative descriptions for the stochastic error of grating-based differential phase contrast imaging (DPCi). Our model includes the noise transfer characteristics of the x-ray detector and the jitter of the phase steps. We find that the noise in DPCi depends strongly on the phase stepping visibility and the sample properties. The results are supported by experimental evidence acquired with our new instrument with a field of view of 50x70 mm(2). Our conclusions provide general guidelines to optimize grating interferometers for specific applications and problems.

Performance and optimization of X-ray grating interferometry

“…The fringe visibility is different from the true visbility of the phase stepping curve; however, they are proportional if an ideal G2 (τ 2 = 0) is used. From the polychromatic visibility, the smallest detectable refraction angle with a polychromatic beam can be obtained by using equation (2.24), although this is only valid if there is no object in the beam (flat field) [18,21]. With an object, this is an approximation which neglects the dispersion.…”

“…The noise standard deviation of the signal, given by σ ϕ , depends on the number of counts N on the detector (analogue-to-digital units; ADUs), on the visibility V and on the detector-specific parameter χ det , which specifies the number of ADUs per incoming photon [18,19]. Other sources of noise such as jitter from mechanical instabilities or aliasing owing to the discrete sampling of the phase-stepping curve are not considered here.…”

EVITA Project: Comparison Between Traditional Non-Destructive Techniques and Phase Contrast X-Ray Imaging Applied to Aerospace Carbon Fibre Reinforced Polymer

“…2a). In contrast to the absorption image, the refraction image is thus related to the refraction coefficient as well as to the thickness of the sample [4]. Finally, the scattering image is related to the ultra-small angle X-ray scattering of the beam inside the sample.…”

“…The phase contrast X-ray imaging system developed here is based on the Talbot-Lau grating interferometer [4]. The grating interferometer consists of a conventional X-ray source, a commercial X-ray detector and three X-ray gratings G0, G1, and G2 as shown in Fig.…”

“…Grating-based Phase Contrast X-Ray Imaging is based on the so-called Talbot-Lau interferometer, which is made of the combination of a standard X-ray apparatus with three transmission gratings as documented in the literature [1][2][3][4]. The method derives its potential from the fact that three different contrast mechanisms are combined in a single measurement.…”