Optimization of Waveguide Optics for Lensless X-ray Imaging
Optimization of Waveguide Optics for Lensless X-ray Imaging

Author: Sven Philip Krüger

Publisher: Universitätsverlag Göttingen

Published: 2011

Total Pages: 169

ISBN-13: 3863950151

DOWNLOAD EBOOK

Lensless x-ray imaging is a promising method to determine the three-dimensional structure of material science and biological specimens at the nanoscale. The development of this technique is strongly related to the optimization of x-ray optics since the image formation and object reconstruction depend significantly on the properties of the illumination wave-field. Waveguide optics act as quasi-point sources and enable the spatial and coherent filtering of x-ray beams. Up to now, x-ray waveguides were severely limited in transmission and flux, restricting their use to high-contrast test structures with moderate resolution and long accumulation times. To overcome these limitations, a novel waveguide design with an optimized refractive index profile is presented which significantly minimizes the absorption of the modes propagating inside the waveguide. Experimental results along with simulations show that these two-component planar x-ray waveguides provide small beam cross-sections along with a high photon flux at the exit. By a serial arrangement of two waveguide slices an optimized illumination source has been developed for high-resolution microscopy, as demonstrated in proof-of-concept imaging experiments.

Advanced x-ray multilayer waveguide optics
Advanced x-ray multilayer waveguide optics

Author: Qi Zhong

Publisher: Göttingen University Press

Published: 2017

Total Pages: 164

ISBN-13: 3863953258

DOWNLOAD EBOOK

The aim of this thesis was to design novel waveguide structures, and to analyze them in view of complex phenomena of near-field propagation. For this purpose, experimental far-field measurements were used in combination with finite-difference simulations and phase retrieval methods. Two novel structures have been designed, fabricated and characterized: the waveguide array (WGA), yielding several waveguided beams in transmission, and multi-guide resonate beam couplers (RBCs), tailored to yield two or several reflected beams. Two novel structures have been designed, fabricated and characterized: the WGA, yielding several waveguided beams in transmission, and multi-guide RBCs, tailored to yield two or several reflected beams. The WGA and the multi-guide RBCs are not only distinct in the coupling geometry. A major difference is related to the fact that the WGA principle is based on the separation (non coupling) of the different transmitted wavelets, while the RBC functions are based on a strong coupling of guided radiation in several layers.

Cone-beam X-ray Phase Contrast Tomography of Biological Samples
Cone-beam X-ray Phase Contrast Tomography of Biological Samples

Author: Matthias Bartels

Publisher: Universitätsverlag Göttingen

Published: 2013

Total Pages: 220

ISBN-13: 3863951344

DOWNLOAD EBOOK

Three-dimensional information of entire objects can be obtained by the remarkable technique of computed tomography (CT). In combination with phase sensitive X-ray imaging high contrast for soft tissue structures can be achieved as opposed to CT based on classical radiography. In this work biological samples ranging from micrometer sized single cells over multi-cellular nerve tissue to entire millimeter sized organs are investigated by use of cone-beam propagationbased X-ray phase contrast. Optimization with respect to contrast, resolution and field of view is achieved by addressing instrumentation, sample preparation and phase reconstruction techniques. By using laboratory sources functional soft tissue within the bony capsule of mouse cochleae is visualized in 3D with unprecedented image quality. At synchrotron storage rings the technique reveals more than 1000 axons running in parallel within a mouse nerve and enables doseefficient three-dimensional cellular imaging as well as two-dimensional imaging at high resolutions below 50 nm.

Biomedical Imaging
Biomedical Imaging

Author: Tim Salditt

Publisher: Walter de Gruyter GmbH & Co KG

Published: 2017-10-23

Total Pages: 358

ISBN-13: 3110426692

DOWNLOAD EBOOK

Covering both physical as well as mathematical and algorithmic foundations, this graduate textbook provides the reader with an introduction into modern biomedical imaging and image processing and reconstruction. These techniques are not only based on advanced instrumentation for image acquisition, but equally on new developments in image processing and reconstruction to extract relevant information from recorded data. To this end, the present book offers a quantitative treatise of radiography, computed tomography, and medical physics. Contents Introduction Digital image processing Essentials of medical x-ray physics Tomography Radiobiology, radiotherapy, and radiation protection Phase contrast radiography Object reconstruction under nonideal conditions

Coherent X-ray diffractive imaging on the single-cell-level of microbial samples
Coherent X-ray diffractive imaging on the single-cell-level of microbial samples

Author: Robin Niklas Wilke

Publisher: Göttingen University Press

Published: 2015

Total Pages: 254

ISBN-13: 3863951905

DOWNLOAD EBOOK

Since its first experimental demonstration in 1999, Coherent X-Ray Diffractive Imaging has become one of the most promising high resolution X-Ray imaging techniques using coherent radiation produced by brilliant synchrotron storage rings. The ability to directly invert diffraction data with the help of advanced algorithms has paved the way for microscopic investigations and wave-field analyses on the spatial scale of nanometres without the need for inefficient imaging lenses. X-Ray phase contrast which is a measure of the electron density is an important contrast mode of soft biological specimens. For the case of many dominant elements of soft biological matter, the electron density can be converted into an effective mass density offering a unique quantitative information channel which may shed light on important questions such as DNA compaction in the bacterial nucleoid through ‚weighing with light‘. In this work X-Ray phase contrast maps have been obtained from different biological samples by exploring different methods. In particular, the techniques Ptychography and Waveguide-Holographic-Imaging have been used to obtain twodimensional and three-dimensional mass density maps on the single-cell-level of freeze-dried cells of the bacteria Deinococcus radiodurans, Bacillus subtilis and Bacillus thuringiensis allowing, for instance, to estimate the dry weight of the bacterial genome in a near native state. On top of this, reciprocal space information from coherent small angle X-Ray scattering (cellular Nano-Diffraction) of the fine structure of the bacterial cells has been recorded in a synergistic manner and has been analysed down to a resolution of about 2.3/nm exceeding current limits of direct imaging approaches. Furthermore, the dynamic range of present detector technology being one of the major limiting factors of ptychographic phasing of farfield diffraction data has been significantly increased. Overcoming this problem for the case of the very intense X-Ray beam produced by Kirkpatrick-Baez mirrors has been explored by using semi-transparent central stops.

3d virtual histology of neuronal tissue by propagation-based x-ray phase-contrast tomography
3d virtual histology of neuronal tissue by propagation-based x-ray phase-contrast tomography

Author: Mareike Töpperwien

Publisher: Göttingen University Press

Published: 2018

Total Pages: 286

ISBN-13: 3863953649

DOWNLOAD EBOOK

Deciphering the three-dimensional (3d) cytoarchitecture of neuronal tissue is an important step towards understanding the connection between tissue function and structure and determining relevant changes in neurodegenerative diseases. The gold standard in pathology is histology, in which the tissue is examined under a light microscope after serial sectioning and subsequent staining. It is an invasive and labor-intensive technique which is prone to artifacts due to the slicing procedure. While it provides excellent results on the 2d slices, the 3d anatomy can only be determined after aligning the individual sections, leading to a non-isotropic resolution within the tissue. X-ray computed tomography (CT) offers a promising alternative due to its potential resolution and large penetration depth which allows for non-invasive imaging of the sample's 3d density distribution. In classical CT, contrast formation is based on absorption of the x-rays as they pass through the sample. However, weakly absorbing samples like soft tissue from the central nervous system give nearly no contrast. By exploiting the much stronger phase shifts for contrast formation, which the sample induces in a (partially) coherent wavefront, it can be substantially increased. During free-space propagation behind the sample, these phase shifts are converted to a measurable intensity image by interference of the disturbed wave fronts. In this thesis, 3d virtual histology is performed by means of propagation-based x-ray phase-contrast tomography on tissue from the central nervous system of humans and mice. A combination of synchrotron-based and laboratory setups is used to visualize the 3d density distribution on varying lengths scales from the whole organ down to single cells. By comparing and optimizing different preparation techniques and phase-retrieval approaches, even sub-cellular resolution can be reached in mm-sized tissue blocks. The development of an automatic cell segmentation workflow provides access to the 3d cellular distribution within the tissue, enabling the quantification of the cellular arrangement and allowing for extensive statistical analysis based on several thousands to millions of cells. This paves the way for biomedical studies aimed at changes in cellular distribution, e.g., in the course of neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease or ischemic stroke.

Cone-beam x-ray phase-contrast tomography for the observation of single cells in whole organs
Cone-beam x-ray phase-contrast tomography for the observation of single cells in whole organs

Author: Martin Krenkel

Publisher: Göttingen University Press

Published: 2015

Total Pages: 238

ISBN-13: 3863952510

DOWNLOAD EBOOK

X-ray imaging enables the nondestructive investigation of interior structures in otherwise opaque samples. In particular the use of computed tomography (CT) allows for arbitrary virtual slices through the object and 3D information about intricate structures can be obtained. However, when it comes to image very small structures like single cells, the classical CT approach is limited by the weak absorption of soft-tissue. The use of phase information, encoded in measureable intensity images by free-space propagation of coherent x-rays, allows a huge increase in contrast, which enables 3D reconstructions at higher resolutions. In this work the application of propagation-based phase-contrast tomography to lung tissue samples is demonstrated in close to in vivo conditions. Reconstructions of the lung structure of whole mice at down to 5 μm resolution are obtained at a selfbuilt CT setup, which is based on a liquid-metal jet x-ray source. To reach even higher resolutions, synchrotron radiation in combination with suitable holographic phase-retrieval algorithms is employed. Due to optimized cone-beam geometry, field of view and resolution can be varied over a wide range of parameters, so that information on different length scales can be achieved, covering several millimeters field of view down to a 3D resolution of 50 nm. Thus, the sub-cellular 3D imaging of single cells embedded in large pieces of tissue is enabled, which paves the way for future biomedical research.

Nanoscale Photonic Imaging
Nanoscale Photonic Imaging

Author: Tim Salditt

Publisher: Springer Nature

Published: 2020-06-09

Total Pages: 634

ISBN-13: 3030344134

DOWNLOAD EBOOK

This open access book, edited and authored by a team of world-leading researchers, provides a broad overview of advanced photonic methods for nanoscale visualization, as well as describing a range of fascinating in-depth studies. Introductory chapters cover the most relevant physics and basic methods that young researchers need to master in order to work effectively in the field of nanoscale photonic imaging, from physical first principles, to instrumentation, to mathematical foundations of imaging and data analysis. Subsequent chapters demonstrate how these cutting edge methods are applied to a variety of systems, including complex fluids and biomolecular systems, for visualizing their structure and dynamics, in space and on timescales extending over many orders of magnitude down to the femtosecond range. Progress in nanoscale photonic imaging in Göttingen has been the sum total of more than a decade of work by a wide range of scientists and mathematicians across disciplines, working together in a vibrant collaboration of a kind rarely matched. This volume presents the highlights of their research achievements and serves as a record of the unique and remarkable constellation of contributors, as well as looking ahead at the future prospects in this field. It will serve not only as a useful reference for experienced researchers but also as a valuable point of entry for newcomers.

Wave Optical Simulations of X-ray Nano-focusing Optics
Wave Optical Simulations of X-ray Nano-focusing Optics

Author: Markus Osterhoff

Publisher: Universitätsverlag Göttingen

Published: 2012

Total Pages: 167

ISBN-13: 3863950542

DOWNLOAD EBOOK

Curved x-ray multilayer mirrors focus synchrotron beams down to tens of nano metres. A wave-optical theory describing propagation of two waves in an elliptically curved focusing multilayer mirror is developed in this thesis. Using numerical integration, the layer shapes can be optimised for reflectivity and aberrations. Within this framework, performance of both existing and currently upgraded synchrotron beamlines is simulated. Using a more theoretical model case, limits of the theory are studied. A significant part of this work is dedicated to partial spatial coherence, modelled using the method of stochastic superpositions. Coherence propagation and filtering by x-ray waveguides is shown analytically and numerically. This comprehensive model is put forward that shall help in development and testing of new algorithms for a variety of imaging techniques using coherent x-ray beams. Advanced simulations accounting for real structure effects are compared to experimental data obtained at the GINIX instrument at the coherence beamline P10 at PETRA III, DESY. This thesis presents results of a collaboration between the Georg-August-Universität Göttingen and the European Synchrotron Radiation Facility (ESRF) Grenoble.