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Dive into the research topics where Danays Kunka is active.

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Featured researches published by Danays Kunka.


INTERNATIONAL WORKSHOP ON X-RAY AND NEUTRON PHASE IMAGING WITH GRATINGS | 2012

High aspect ratio gratings for X-ray phase contrast imaging

J. Mohr; Thomas Grund; Danays Kunka; Johannes Kenntner; Juerg Leuthold; Jan Meiser; Joachim Schulz; Marco Walter

Differential phase contrast X-ray imaging (DPCI) has gained a lot of interest in the past years. It is based on X-ray grating interferometry and the image quality is strongly dependant on the grating quality. Periodic line and space structures with periods in the micron range are required for the source and absorption grating. In case of energies > 30 keV their height should be larger than 100 μm resulting in aspect ratios of more than 100. Deep X-ray lithography and gold electroforming (LIGA technology) is used to fabricate these challenging structures. After resist, design and process optimization gratings with 2.4 μm period have been electroformed up to 120 μm, Visibilities of up to 70% for 29 keV and up to 20% for 52 keV have been achieved for monochromatic synchrotron light. Structures with larger periods could be manufactured up to 200 μm; further increase of the height and the gratings quality is possible yielding to high performance gratings also for high energies.


Scientific Reports | 2016

Experimental Realisation of High-sensitivity Laboratory X-ray Grating-based Phase-contrast Computed Tomography

Lorenz Birnbacher; Marian Willner; Astrid Velroyen; Mathias Marschner; Alexander Hipp; Jan Meiser; Frieder J. Koch; Tobias J. Schröter; Danays Kunka; Jürgen Mohr; Franz Pfeiffer; Julia Herzen

The possibility to perform high-sensitivity X-ray phase-contrast imaging with laboratory grating-based phase-contrast computed tomography (gbPC-CT) setups is of great interest for a broad range of high-resolution biomedical applications. However, achieving high sensitivity with laboratory gbPC-CT setups still poses a challenge because several factors such as the reduced flux, the polychromaticity of the spectrum, and the limited coherence of the X-ray source reduce the performance of laboratory gbPC-CT in comparison to gbPC-CT at synchrotron facilities. In this work, we present our laboratory X-ray Talbot-Lau interferometry setup operating at 40 kVp and describe how we achieve the high sensitivity yet unrivalled by any other laboratory X-ray phase-contrast technique. We provide the angular sensitivity expressed via the minimum resolvable refraction angle both in theory and experiment, and compare our data with other differential phase-contrast setups. Furthermore, we show that the good stability of our high-sensitivity setup allows for tomographic scans, by which even the electron density can be retrieved quantitatively as has been demonstrated in several preclinical studies.


Physica Medica | 2014

Helical differential X-ray phase-contrast computed tomography

Jian Fu; Marian Willner; Liyuan Chen; Renbo Tan; Klaus Achterhold; Martin Bech; Julia Herzen; Danays Kunka; Juergen Mohr; Franz Pfeiffer

We report on the first experimental results of helical differential phase-contrast computed tomography (helical DPC-CT) with a laboratory X-ray tube source and a Talbot-Lau grating interferometer. The results experimentally verify the feasibility of helical data acquisition and reconstruction in phase-contrast imaging, in analogy to its use in clinical CT systems. This allows fast and continuous volumetric scans for long objects with lengths exceeding the dimension of the detector. Since helical CT revolutionized the field of medical CT several years ago, we anticipate that this method will bring the same significant impact on the future medical and industrial applications of X-ray DPC-CT.


Scientific Reports | 2017

In-vivo X-ray Dark-Field Chest Radiography of a Pig

Lukas B. Gromann; Fabio De Marco; Konstantin Willer; Peter B. Noël; Kai Scherer; Bernhard Renger; Bernhard Gleich; Klaus Achterhold; Alexander A. Fingerle; Daniela Muenzel; Sigrid Auweter; Katharina Hellbach; Maximilian F. Reiser; Andrea Baehr; Michaela Dmochewitz; Tobias J. Schroeter; Frieder J. Koch; Pascal Meyer; Danays Kunka; Juergen Mohr; Andre Yaroshenko; Hanns-Ingo Maack; Thomas Pralow; Hendrik van der Heijden; Roland Proksa; Thomas Koehler; Nataly Wieberneit; Karsten Rindt; Ernst J. Rummeny; Franz Pfeiffer

X-ray chest radiography is an inexpensive and broadly available tool for initial assessment of the lung in clinical routine, but typically lacks diagnostic sensitivity for detection of pulmonary diseases in their early stages. Recent X-ray dark-field (XDF) imaging studies on mice have shown significant improvements in imaging-based lung diagnostics. Especially in the case of early diagnosis of chronic obstructive pulmonary disease (COPD), XDF imaging clearly outperforms conventional radiography. However, a translation of this technique towards the investigation of larger mammals and finally humans has not yet been achieved. In this letter, we present the first in-vivo XDF full-field chest radiographs (32 × 35 cm2) of a living pig, acquired with clinically compatible parameters (40 s scan time, approx. 80 µSv dose). For imaging, we developed a novel high-energy XDF system that overcomes the limitations of currently established setups. Our XDF radiographs yield sufficiently high image quality to enable radiographic evaluation of the lungs. We consider this a milestone in the bench-to-bedside translation of XDF imaging and expect XDF imaging to become an invaluable tool in clinical practice, both as a general chest X-ray modality and as a dedicated tool for high-risk patients affected by smoking, industrial work and indoor cooking.


Review of Scientific Instruments | 2017

Large field-of-view tiled grating structures for X-ray phase-contrast imaging

Tobias J. Schröter; Frieder J. Koch; Pascal Meyer; Danays Kunka; Jan Meiser; Konstantin Willer; Lukas B. Gromann; Fabio De Marco; Julia Herzen; Peter B. Noël; Andre Yaroshenko; Andreas Hofmann; Franz Pfeiffer; Jürgen Mohr

X-ray grating-based interferometry promises unique new diagnostic possibilities in medical imaging and materials analysis. To transfer this method from scientific laboratories or small-animal applications to clinical radiography applications, compact setups with a large field of view (FoV) are required. Currently the FoV is limited by the grating area, which is restricted due to the complex manufacturing process. One possibility to increase the FoV is tiling individual grating tiles to create one large area grating mounted on a carrier substrate. We investigate theoretically the accuracy needed for a tiling process in all degrees of freedom by applying a simulation approach. We show how the resulting precision requirements can be met using a custom-built frame for exact positioning. Precise alignment is achieved by comparing the fringe patterns of two neighboring grating tiles in a grating interferometer. With this method, the FoV can be extended to practically any desired length in one dimension. First results of a phase-contrast scanning setup with a full FoV of 384 mm × 24 mm show the suitability of this method.


Applied Physics Letters | 2015

X-ray grating interferometry at photon energies over 180 keV

Maite Ruiz-Yaniz; Frieder J. Koch; Irene Zanette; Alexander Rack; Pascal Meyer; Danays Kunka; A. Hipp; Jürgen Mohr; Franz Pfeiffer

We report on the implementation and characterization of grating interferometry operating at an x-ray energy of 183 keV. With the possibility to use this technique at high x-ray energies, bigger specimens could be studied in a quantitative way. Also, imaging strongly absorbing specimens will benefit from the advantages of the phase and dark-field signals provided by grating interferometry. However, especially at these high photon energies the performance of the absorption grating becomes a key point on the quality of the system, because the grating lines need to keep their small width of a couple of micrometers and exhibit a greater height of hundreds of micrometers. The performance of high aspect ratio absorption gratings fabricated with different techniques is discussed. Further, a dark-field image of an alkaline multicell battery highlights the potential of high energy x-ray grating based imaging.


Optics Express | 2014

Non-binary phase gratings for x-ray imaging with a compact Talbot interferometer

Andre Yaroshenko; Martin Bech; Guillaume Potdevin; Andreas Malecki; Thomas Biernath; Johannes Wolf; Arne Tapfer; Markus Schüttler; Jan Meiser; Danays Kunka; Maximilian Amberger; Juergen Mohr; Franz Pfeiffer

X-ray imaging using a Talbot-Lau interferometer, consisting of three binary gratings, is a well-established approach to acquire x-ray phase-contrast and dark-field images with a polychromatic source. However, challenges in the production of high aspect ratio gratings limit the construction of a compact setup for high x-ray energies. In this study we consider the use of phase gratings with triangular-shaped structures in an x-ray interferometer and show that such gratings can yield high visibilities for significantly shorter propagation distances than conventional gratings with binary structures. The findings are supported by simulation and experimental results for both cases of a monochromatic and a polychromatic source.


Physics in Medicine and Biology | 2016

On the origin and nature of the grating interferometric dark-field contrast obtained with low-brilliance x-ray sources.

Thomas Koenig; Marcus Zuber; Barbara Trimborn; Tomas Farago; Pascal Meyer; Danays Kunka; Frederic Albrecht; Sascha Kreuer; Thomas Volk; Michael Fiederle; Tilo Baumbach

The x-ray dark-field contrast accessible via grating interferometry is sensitive to features at length scales well below what is resolvable by a detector system. It is commonly explained as arising from small-angle x-ray scattering (SAXS), and can be implemented both at synchrotron beamlines and with low-brilliance sources such as x-ray tubes. Here, we demonstrate that for tube based setups the underlying process of image formation can be fundamentally different. For focal spots or detector pixels that comprise multiple grating periods, we show that dark-field images contain a strong artificial and system-specific component not arising from SAXS. Based on experiments carried out with a nanofocus x-ray tube and the example of an excised rat lung, we demonstrate that the dark-field contrast observed for porous media transforms into a differential phase contrast for large geometric magnifications. Using a photon counting detector with an adjustable point spread function, we confirm that a dark-field image can indeed be formed by an intra-pixel differential phase contrast that cannot be resolved as such due to a dephasing between the periodicities of the absorption grating and the Talbot carpet. Our findings are further corroborated by a link between the strength of this pseudo-dark-field contrast and our x-ray tubes focal spot size in a three-grating setup. These results must not be ignored when measurements are intended to be reproducible across systems.


EPL | 2014

Cone-beam differential phase-contrast laminography with x-ray tube source

Jian Fu; Thomas Biernath; Marian Willner; Maximilian Amberger; Jan Meiser; Danays Kunka; Jürgen Mohr; Julia Herzen; Martin Bech; Franz Pfeiffer

We report on an x-ray cone-beam differential phase-contrast computed laminography (DPC-CL) method for tomographic reconstruction of thin and lamellar objects. We describe the specific scan geometry of DPC-CL, which consists of a Talbot-Lau grating interferometer and a lab-based x-ray tube source, and derive a filtered back-projection (FBP) reconstruction algorithm. The experimental results of a flat sphere phantom and a piece of ham demonstrate the validity of the proposed technique. The existing DPC-CL methods are based on synchrotron sources and the parallel-beam geometry. In contrast, our approach adopts a more accessible x-ray tube source and a cone-beam geometry. Therefore it significantly widens the application range of phase-contrast laminography, particularly in practical laboratory settings, beyond applications at large-scale synchrotron facilities.


Review of Scientific Instruments | 2015

Note: Gratings on low absorbing substrates for x-ray phase contrast imaging

Frieder J. Koch; Tobias J. Schröter; Danays Kunka; Pascal Meyer; Jan Meiser; A. Faisal; M. I. Khalil; Lorenz Birnbacher; M. Viermetz; Marco Walter; Joachim Schulz; Franz Pfeiffer; Jürgen Mohr

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.

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Jürgen Mohr

Karlsruhe Institute of Technology

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Pascal Meyer

Karlsruhe Institute of Technology

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Frieder J. Koch

Karlsruhe Institute of Technology

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Jan Meiser

Karlsruhe Institute of Technology

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Tobias J. Schröter

Karlsruhe Institute of Technology

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Maximilian Amberger

Karlsruhe Institute of Technology

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Tilo Baumbach

Karlsruhe Institute of Technology

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A. Faisal

Karlsruhe Institute of Technology

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Andreas Hofmann

Karlsruhe Institute of Technology

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Joachim Schulz

Karlsruhe Institute of Technology

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