Karlsruhe, Germany
Karlsruhe, Germany

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Meiser J.,Karlsruhe Institute of Technology | Amberger M.,TU Munich | Willner M.,Helmholtz Center Geesthacht | Kunka D.,Microworks GmbH | And 6 more authors.
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2014

X-ray phase contrast imaging has become a promising biomedical imaging technique for enhancing soft-tissue contrast. In addition to an absorption contrast image it provides two more types of image, a phase contrast and a small-Angle scattering contrast image recorded at the same time. In biomedical imaging their combination allows for the conventional investigation of e.g. bone fractures on the one hand and for soft-tissue investigation like cancer detection on the other hand. Among the different methods of X-ray phase contrast imaging the grating based approach, the Talbot-Lau interferometry, has the highest potential for commercial use in biomedical imaging at the moment, because commercially available X-ray sources can be used in a compact setup. In Talbot-Lau interferometers, core elements are phase and absorption gratings with challenging specifications because of their high aspect ratios (structure height over width). For the long grating lamellas structural heights of more than 100 Î=m together with structural width in the micron range are requested. We are developing a fabrication process based on deep x-ray lithography and electroforming (LIGA) to fabricate these challenging structures. In case of LIGA gratings the structural area is currently limited to several centimeters by several centimeters which limit the field of view in grating based X-ray phase contrast imaging. In order to increase the grating area significantly we are developing a stitching method for gratings using a 625 Î=m thick silicon wafer as a carrier substrate. In this work we compare the silicon carrier with an alternative one, polyimide, for patient dose reduction and for the use at lower energies in terms of transmission and image reconstruction problems. © 2014 SPIE.


Kunka D.,Karlsruhe Institute of Technology | Mohr J.,Karlsruhe Institute of Technology | Nazmov V.,Karlsruhe Institute of Technology | Meiser J.,Karlsruhe Institute of Technology | And 9 more authors.
Microsystem Technologies | Year: 2014

At the Karlsruhe Institute of Technology (KIT), Institute of Micro Structure Technology (IMT) high aspect ratio (HAR) micro structures are manufactured by means of deep X-ray lithography and gold electroplating (LIGA technology). The technology is used to fabricate grating structures for differential phase contrast X-ray imaging (DPCI). Using an epoxy based negative resist material; electroplated grating structures are fabricated having absorber lamellas with heights up to 100 μm and a period down to 2.4 μm. However, in DPCI there is an increasing demand for improved quality gratings with periods down to 1 μm, areas larger than 50 mm × 50 mm with a high homogeneity in terms of the lamella height distribution and defect-free grating patterns. Pattern deformations are due to limited mechanical stability of the resist during the development process as well as to resist shrinkage during crosslinking, affecting mostly gratings with small periods and HARs. The purpose of this contribution is to present a methodology for the characterization of different epoxy based negative resist formulations, aiming to increase the quality of the HAR free standing grating lamellas by increased mechanical stability of the resist. © 2013 Springer-Verlag Berlin Heidelberg.


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.


Koch F.J.,Karlsruhe Institute of Technology | Schroter T.J.,Karlsruhe Institute of Technology | Kunka D.,Karlsruhe Institute of Technology | Meyer P.,Karlsruhe Institute of Technology | And 9 more authors.
Review of Scientific Instruments | Year: 2015

Grating based X-ray phase contrast imaging is on the verge of being applied in clinical settings. To achieve this goal, compact setups with high sensitivity and dose efficiency are necessary. Both can be increased by eliminating unwanted absorption in the beam path, which is mainly due to the grating substrates. Fabrication of gratings via deep X-ray lithography can address this issue by replacing the commonly used silicon substrate with materials with lower X-ray absorption that fulfill certain boundary conditions. Gratings were produced on both graphite and polymer substrates without compromising on structure quality. These gratings were tested in a three-grating setup with a source operated at 40 kVp and lead to an increase in the detector photon count rate of almost a factor of 4 compared to a set of gratings on silicon substrates. As the visibility was hardly affected, this corresponds to a significant increase in sensitivity and therefore dose efficiency. © 2015 AIP Publishing LLC.


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.


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.


PubMed | Karlsruhe Institute of Technology, Friedrich - Alexander - University, Erlangen - Nuremberg, TU Munich and Microworks GmbH
Type: Journal Article | Journal: 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 22 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.


PubMed | Karlsruhe Institute of Technology, TU Munich and Microworks GmbH
Type: Journal Article | Journal: The Review of scientific instruments | Year: 2016

Grating based X-ray phase contrast imaging is on the verge of being applied in clinical settings. To achieve this goal, compact setups with high sensitivity and dose efficiency are necessary. Both can be increased by eliminating unwanted absorption in the beam path, which is mainly due to the grating substrates. Fabrication of gratings via deep X-ray lithography can address this issue by replacing the commonly used silicon substrate with materials with lower X-ray absorption that fulfill certain boundary conditions. Gratings were produced on both graphite and polymer substrates without compromising on structure quality. These gratings were tested in a three-grating setup with a source operated at 40 kVp and lead to an increase in the detector photon count rate of almost a factor of 4 compared to a set of gratings on silicon substrates. As the visibility was hardly affected, this corresponds to a significant increase in sensitivity and therefore dose efficiency.


Khimchenko A.,University of Basel | Schulz G.,University of Basel | Deyhle H.,University of Basel | Hieber S.E.,University of Basel | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

X-ray imaging in the absorption contrast mode is an established method of visualising calcified tissues such as bone and teeth. Physically soft tissues such as brain or muscle are often imaged using magnetic resonance imaging (MRI). However, the spatial resolution of MRI is insufficient for identifying individual biological cells within three-dimensional tissue. X-ray grating interferometry (XGI) has advantages for the investigation of soft tissues or the simultaneous three-dimensional visualisation of soft and hard tissues. Since laboratory microtomography (μCT) systems have better accessibility than tomography set-ups at synchrotron radiation facilities, a great deal of effort has been invested in optimising XGI set-ups for conventional μCT systems. In this conference proceeding, we present how a two-grating interferometer is incorporated into a commercially available nanotom m (GE Sensing and Inspection Technologies GmbH) μCT system to extend its capabilities toward phase contrast. We intend to demonstrate superior contrast in spiders (Hogna radiata (Fam. Lycosidae) and Xysticus erraticus (Fam. Thomisidae)), as well as the simultaneous visualisation of hard and soft tissues. XGI is an imaging modality that provides quantitative data, and visualisation is an important part of biomimetics; consequently, hard X-ray imaging provides a sound basis for bioinspiration, bioreplication and biomimetics and allows for the quantitative comparison of biofabricated products with their natural counterparts. © 2016 SPIE.

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