Fabrication of diffraction gratings for hard X-ray phase contrast imaging

Paul Scherrer Institut, CH 5232 Villigen-PSI, Switzerland
Microelectronic Engineering (Impact Factor: 1.34). 05/2007; DOI: 10.1016/j.mee.2007.01.151

ABSTRACT We have developed a method for X-ray phase contrast imaging, which is based on a grating interferometer. The technique is capable of recording the phase shift of hard X-rays travelling through a sample, which greatly enhances the contrast of low absorbing specimen compared to conventional amplitude contrast images. Unlike other existing X-ray phase contrast imaging methods, the grating interferometer also works with incoherent radiation from a standard X-ray tube. The key components are three gratings with silicon and gold structures, which have dimensions in the micrometer range and high aspect ratios. The fabrication processes, which involve photolithography, anisotropic wet etching, and electroplating, are described in this article for each of the three gratings. An example of an X-ray phase contrast image acquired with the grating interferometer is given.


Available from: Ana Diaz, Jun 02, 2015
1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Talbot-Lau grating interferometer enables refraction based imaging with conventional X-ray tubes, offering the promise of a new medical imaging modality. The fringe contrast of the normal incidence interferometer is however insufficient at the >40 keV photon energies needed to penetrate thick body parts, because the thin absorption gratings used in the interferometer become transparent. To solve this problem we developed a new interferometer design using gratings at glancing incidence. For instance, using 120 μm thick Au gratings at 10° incidence we increased several fold the interferometer contrast for a spectrum with ~58 keV mean energy. Tests of DPC-CT at 60-80kVp using glancing angle interferometers and medically relevant samples indicate high potential for clinical applications. A practical design for a slot-scan DPC-CT system for the knee is proposed, using glancing angle gratings tiled on a single substrate.
    SPIE Medical Imaging; 03/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of beam hardening have previously been extended from absorption imaging to phase contrast imaging, showing a similar, albeit reduced, effect in the phase images. The effect of beam hardening on the interferometer performance, however, has not been demonstrated. In this work, the visibility reduction on a differential phase contrast imaging system due to spectral changes as a result of beam hardening is demonstrated. The implication of this reduction is an artificial increase in noise for the phase contrast image through highly-attenuating regions of the object. In addition, false signal will be recorded in the dark-field image, which normally shows only highly-scattering objects and interfaces. The results show that with added beam filtration, the effect is reduced, just as with more traditional beam hardening artifacts. However, the effect also means that one must also take into account the desired imaging task when determining the system’s design energy.
    SPIE Medical Imaging; 03/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Among X-ray phase-contrast techniques, grating-based X-ray differential phase contrast (DPC) imaging using conventional X-ray tube sources is the most prominent one for widespread applications in the case of acquisition of high-quality absorption gratings in mass production. In this letter, we report on a new type of absorption grating made from Bi and manufactured by a micro-casting process. We tested Bi absorption gratings with our X-ray DPC imaging system and obtained high-quality phase-contrast images. Our efforts towards the practical application of X-ray DPC imaging are briefly outlined. (C) 2013 The Japan Society of Applied Physics
    Applied Physics Express 11/2013; 6(11):117301. DOI:10.7567/APEX.6.117301 · 2.57 Impact Factor