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

Paul Scherrer Institut, CH 5232 Villigen-PSI, Switzerland
Microelectronic Engineering (Impact Factor: 1.2). 05/2007; 84(5-8):1172-1177. DOI: 10.1016/j.mee.2007.01.151


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.

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    • "The period g 2 of grating G2 was 2 μm, which is equal to the interference fringe period caused by grating G1. The source grating G0 has a period of g 0 = g 2 × L/d = 14 μm, ensuring that the interference patterns from neighboring source lines will overlap at G2 (David et al 2007a). The sample should be located immediately in front of G1, and the detector should be immediately behind G2. "
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    ABSTRACT: We report the first experimental soft-tissue phase-contrast tomography results using a conventional x-ray tube source, with a millimeter-sized focal spot. The setup is based on a Talbot-Lau grating interferometer operated at a mean energy of 28 keV. We present three-dimensional ex vivo images of a chicken heart sample, fixated in formalin. The results clearly demonstrate the advantageous contrast attainable through phase-contrast imaging over conventional attenuation-based approaches.
    Physics in Medicine and Biology 05/2009; 54(9):2747-53. DOI:10.1088/0031-9155/54/9/010 · 2.76 Impact Factor
    • "(Orange graph) Spectrum w(E ) considering anode self-absorption, 1 mm Be window and 1689 mm air in the beam path, only; (black graph) effective spectrum w eff (E ) according to Eq. (18), which also comprises the detection efficiency of the 600 µm thick CsI scintillator and beam hardening due to the two 280-µm-thick Si wafers of the gratings, a 1-µm-thick gold layer on the analyzer grating (cf. David et al., 2007) and the 0.5-mm-thick amorphous carbon scintillator substrate (absorption coefficients from Hubbell & Seltzer, 1995). "
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    ABSTRACT: The influence of different physical parameters, such as the source size and the energy spectrum, on the functional capability of a grating interferometer applied for phase-contrast imaging is discussed using numerical simulations based on Fresnel diffraction theory. The presented simulation results explain why the interferometer could be well combined with polychromatic laboratory x-ray sources in recent experiments. Furthermore, it is shown that the distance between the two gratings of the interferometer is not in general limited by the width of the photon energy spectrum. This implies that interferometers that give a further improved image quality for phase measurements can be designed, because the primary measurement signal for phase measurements can be increased by enlargement of this distance. Finally, the mathematical background and practical instructions for the quantitative evaluation of measurement data acquired with a polychromatic x-ray source are given.
    Journal of Microscopy 11/2008; 232(1):145-57. DOI:10.1111/j.1365-2818.2008.02072.x · 2.33 Impact Factor
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    • "The corresponding values for the second grating (gold absorber grating, G2) were p 2 = 2.00 µm and h 2 = 30 µm. In contrast to the earlier experiments (Weitkamp et al 2005), a novel grating fabrication protocol was used (David et al 2007). This allowed the fabrication of unprecedentedly high aspect ratios (60:1) for the absorbing lines of the analyzer grating (G2), thus increasing the contrast of the intensity modulation recorded during a phase-stepping scan. "
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    ABSTRACT: We report on significant advances and new results concerning a recently developed method for grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique is increased and show in vitro tomographic images of a tumor bearing rat brain sample, without use of contrast agents. In particular, we observe that the brain tumor and the white and gray brain matter structure in a rat's cerebellum are clearly resolved. The results are potentially interesting from a clinical point of view, since a similar approach using three transmission gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes. Moreover, the results open the way to in vivo experiments in the near future.
    Physics in Medicine and Biology 01/2008; 52(23):6923-30. DOI:10.1088/0031-9155/52/23/010 · 2.76 Impact Factor
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