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Karlsruhe, Germany

Sarapata A.,TU Munich | Willner M.,TU Munich | Walter M.,Microworks GmbH | Duttenhofer T.,Microworks GmbH | And 7 more authors.
Optics Express | Year: 2015

Imaging of large and dense objects with grating-based X-ray phase-contrast computed tomography requires high X-ray photon energy and large fields of view. It has become increasingly possible due to the improvements in the grating manufacturing processes. Using a high-energy X-ray phase-contrast CT setup with a large (10 cm in diameter) analyzer grating and operated at an acceleration tube voltage of 70 kVp, we investigate the complementarity of both attenuation and phase contrast modalitieswith materials of various atomic numbers (Z). We confirm experimentally that for low-Z materials, phase contrast yields no additional information content over attenuation images, yet it provides increased contrast-to-noise ratios (CNRs). The complementarity of both signals can be seen again with increasing Z of the materials and a more comprehensive material characterization is thus possible. Imaging of a part of a human cervical spine with intervertebral discs surrounded by bones and various soft tissue types showcases the benefit of high-energy X-ray phase-contrast system. Phase-contrast reconstruction reveals the internal structure of the discs and makes the boundary between the disc annulus and nucleus pulposus visible. Despite the fact that it still remains challenging to develop a high-energy grating interferometer with a broad polychromatic source with satisfactory optical performance, improved image quality for phase contrast as compared to attenuation contrast can be obtained and new exciting applications foreseen. © 2015 Optical Society of America.

Bech M.,Technical Universityet Munich | Bech M.,Lund University | Tapfer A.,Technical Universityet Munich | Velroyen A.,Technical Universityet Munich | And 8 more authors.
AIP Conference Proceedings | Year: 2012

After successful demonstrations of soft-tissue phase-contrast imaging with grating interferometers at synchrotron radiation sources and at laboratory based x-ray tubes, a first preclinical CT scanner with grating based phase contrast imaging modality has been constructed. The rotating gantry is equipped with a three-grating interferometer, a 50 watt tungsten anode source and a Hamamatsu flat panel detector. The total length of the interferometer is 45 cm, and the bed of the scanner is optimized for mice, with a scanning diameter of 35 mm. From one single scan both phase-contrast and standard attenuation based tomography can be attained, providing an overall gain in image contrast. © 2012 American Institute of Physics.

Nazmov V.,Karlsruhe Institute of Technology | Reznikova E.,Karlsruhe Institute of Technology | Mohr J.,Karlsruhe Institute of Technology | Schulz J.,Microworks GmbH | Voigt A.,Micro Resist Technology GmbH
Journal of Materials Processing Technology | Year: 2015

A technique of casting of thick pre-polymer layers was developed based on the proposed model of diluent evaporation. For the first time, microstructures with 7 mm height and up to 18 microns wide (an aspect ratio of up to 389) were manufactured by means of ultra deep X-ray lithography in a cured pre-polymer that can be functionalized. The microstructures were characterized. The difference in the size of patterned microstructures and their initial size on the X-ray mask decreases to 400 nm with the lessening lateral dimension of the microstructures from 1500 to 18 μm. The sidewall roughness also decreases to 20 nm. © 2015 Elsevier B.V. All rights reserved.

Kenntner J.,Karlsruhe Institute of Technology | Grund T.,Karlsruhe Institute of Technology | Matthis B.,Karlsruhe Institute of Technology | Boerner M.,Karlsruhe Institute of Technology | And 9 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Phase contrast imaging with conventional X-ray tubes as e.g. in computer tomography scanners (CTscanners) requires a setup of three different types of optical gratings. One grating is used to obtain a spatially coherent radiation, the second grating defines a periodic phase shift and the third is used as a periodic absorption grating. In order to absorb high energy radiation, absorption gratings with periods of a few microns only and extreme aspect ratios (>80) are fabricated, employing a modified LIGA process. However, above a critical structural height, structures collapse due to e.g. capillary effects. To overcome this limitation a new variant of the LIGA process has been developed. It is characterized by structuring of a resist on both sides of a membrane, resulting in a moderate aspect ratio on both sides of the membrane instead of an extreme aspect ratio on one side. To get a perfect overlay of both structures the grating structure on the front side of a membrane patterned by the standard LIGA-process is used as the mask for structuring the second resist layer on the backside of the membrane. A second electroforming step fills the gaps on the backside. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Meiser J.,Karlsruhe Institute of Technology | Willner M.,TU Munich | Schroter T.,Karlsruhe Institute of Technology | Hofmann A.,Karlsruhe Institute of Technology | And 19 more authors.
Journal of X-Ray Science and Technology | Year: 2016

Grating based X-ray differential phase contrast imaging (DPCI) allows for high contrast imaging of materials with similar absorption characteristics. In the last years' publications, small animals or parts of the human body like breast, hand, joints or blood vessels have been studied. Larger objects could not be investigated due to the restricted field of view limited by the available grating area. In this paper, we report on a new stitching method to increase the grating area significantly: individual gratings are merged on a carrier substrate. Whereas the grating fabrication process is based on the LIGA technology (X-ray lithography and electroplating) different cutting and joining methods have been evaluated. First imaging results using a 2×2 stitched analyzer grating in a Talbot-Lau interferometer have been generated using a conventional polychromatic X-ray source. The image quality and analysis confirm the high potential of the stitching method to increase the field of view considerably. © 2016 - IOS Press and the authors. All rights reserved.

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