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Prof. Dr. Simon Zabler

Head of research at TC Plattling
Teaching
Head of Fraunhofer Application Center CT for Measurement Technology CTMT

Faculty of Electrical Engineering and Media Technology

Professors

Professor

ITC2+ 1.10

0991/3615-8247

consulting time

Tuesday 11:30-13:00 and with appointment

publications

Sortierung:

Journal article

Simon Zabler
O. Paris
I. Burgert
P. Fratzl

Moisture changes in the plant cell wall force cellulose crystallites to deform.

In: Journal of Structural Biology vol. 171 pg. 133-41

08.05.2010 (2010)

DOI: 10.1016/j.jsb.2010.04.013

show abstract

Nano-crystallite deformation of cellulose microfibrils in the secondary cell wall layer of spruce wood tracheids was observed during de- and rehydration experiments below the fibre saturation point. A quantitative analysis of the (004), (200) and the (110)/(11 0) doublet X-ray diffraction peaks revealed longitudinal contraction, lateral expansion and changes in the monoclinic angle of the cellulose unit cell during drying of wood fibres. Experiments on unfixed samples as well as the simultaneous application of mechanical tensile and dehydration stress to samples hold at constant length showed two deformation mechanisms of different nature and magnitude. The first mechanism depends on the relative wood moisture content and the second one on the macroscopic tensile stress. These findings imply a new perspective on the role of water adsorption perceiving a hydration-induced structural change of cellulose crystal structure as a major driving force for deformation.

Journal article

Simon Zabler
A. Ershov
A. Rack
F. Garcia-Moreno
T. Baumbach
J. Banhart

Particle and liquid motion in semi-solid aluminium alloys: A quantitative in situ microradioscopy study.

In: Acta Materialia vol. 61 pg. 1244-1253

(2013)

DOI: 10.1016/j.actamat.2012.10.047

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Semi-solid melts exhibit a very unpredictable rheology and filling dynamics, when injected into thin-walled components. Optimization of the process requires an insight into the casting process during injection. For this purpose we injected semi-solid an Al–Ge alloy into two different thin channel geometries while recording high resolution radiographs at fast frame rates (up to 1000 images per s). Comparison of a bottleneck channel, which has previously been used for slower experiments, with a right-angle turn geometry reveals a significant influence of the channel shape on the flow behaviour of the particle–liquid mixture. While the bottleneck is quickly sealed with densified solid, turbulences in the right-angle turn apparently permit solid particles and clusters to move conjointly with the liquid and thus achieve a more complete filling. Single particle trajectories and rapid break-up of solid skeletons in such a system have been observed for the first time in situ.

Journal article

A. Tissen
Peter Hornberger
Jochen Hiller
Simon Zabler
B. Baudrit
S. Horlemann

Dimensionelles Messen und Materialprüfung an belasteten Bauteilen mit In-situ-CT.

In: inspect vol. 15 pg. 54-56

(2014)

show abstract

Die Anwendung der Röntgen-Computertomographie (CT) als zerstörungsfreie Prüfung (zfP) entwickelt sich zunehmend zu einem unverzichtbaren bildgebenden Verfahren in der Qualitätssicherung. Seit dem letzten Jahrzehnt wird diese Technologie verstärkt auch in der dimensionellen Messtechnik eingesetzt.

Contribution

Simon Rettenberger
Peter Hornberger
A. Tissen
Jochen Hiller
Simon Zabler

Messtechnik und Materialprüfung an belasteten Bauteilen mit In-situ-Computertomographie.

In: Leitfaden zur industriellen Röntgentechnik. Zerstörungsfreie Prüfung mit Bildverarbeitung (Vision)

(2015)

Journal article

K. Blum
W. Wiest
C. Fella
A. Balles
J. Dittmann
A. Rack
D. Maier
R. Thomann
B. Spies
R. Kohal
Simon Zabler
K. Nelson

Fatigue induced changes in conical implant-abutment connections.

In: Dental Materials (Academy of Dental Materials) vol. 31 pg. 1415-26

28.09.2015 (2015)

DOI: 10.1016/j.dental.2015.09.004

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OBJECTIVES Based on the current lack of data and understanding of the wear behavior of dental two-piece implants, this study aims for evaluating the microgap formation and wear pattern of different implants in the course of cyclic loading. METHODS Several implant systems with different conical implant-abutment interfaces were purchased. The implants were first evaluated using synchrotron X-ray high-resolution radiography (SRX) and scanning electron microscopy (SEM). The implant-abutment assemblies were then subjected to cyclic loading at 98N and their microgap was evaluated after 100,000, 200,000 and 1 million cycles using SRX, synchrotron micro-tomography (μCT). Wear mechanisms of the implant-abutment connection (IAC) after 200,000 cycles and 1 million cycles were further characterized using SEM. RESULTS All implants exhibit a microgap between the implant and abutment prior to loading. The gap size increased with cyclic loading with its changes being significantly higher within the first 200,000 cycles. Wear was seen in all implants regardless of their interface design. The wear pattern comprised adhesive wear and fretting. Wear behavior changed when a different mounting medium was used (brass vs. polymer). SIGNIFICANCE A micromotion of the abutment during cyclic loading can induce wear and wear particles in conical dental implant systems. This feature accompanied with the formation of a microgap at the IAC is highly relevant for the longevity of the implants.

Journal article

M. Ullherr
Simon Zabler

Correcting multi material artifacts from single material phase retrieved holo-tomograms with a simple 3D Fourier method.

In: Optics Express vol. 23 pg. 32718-27

(2015)

DOI: 10.1364/OE.23.032718

show abstract

Here we present a method for the removal of multi-material artifacts which occur during the application of a single material phase retrieval procedure to X-ray tomographic data sets. For the phase retrieval we chose the most common method which is the single material filter. The correction method which we describe in the following has been designed for samples consisting of three distinct materials, hence effectively two different material interfaces. Furthermore the material phase with the strongest X-ray interaction needs to show sufficient absorption in order to allow for segmenting this phase through application of a grey value threshold. If these conditions are fulfilled the method is easy to apply through post processing as is shown for the volume images of two sample types.

Journal article

S. Horlemann
E. Kraus
B. Baudrit
M. Bastian
A. Tissen
Jochen Hiller
Simon Zabler

In-situ-Prüfungen von Kunststoff-Klebeverbindungen mit Computertomographie.

In: KGK Rubber Point - Kautschuk Gummi Kunststoffe

(2015)

show abstract

Das mechanische Verhalten von geklebten PEEK-Verbindungen wurde unter Belastung mittels Computertomographie in-situ untersucht. Hierbei wurden für eine Zugscher-Probe die Dehnungsverteilungen in der gesamten Klebeverbindung sowie in der Klebeebene lokal bei einem mehraxialen Zustand analysiert.

Journal article

W. Wiest
Simon Zabler
A. Rack
C. Fella
A. Balles
K. Nelson
R. Schmelzeisen
R. Hanke

In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants.

In: Journal of Synchrotron Radiation vol. 22 pg. 1492-7

09.10.2015 (2015)

DOI: 10.1107/S1600577515015763

show abstract

Synchrotron real-time radioscopy and in situ microtomography are the only techniques providing direct visible information on a micrometre scale of local deformation in the implant-abutment connection (IAC) during and after cyclic loading. The microgap formation at the IAC has been subject to a number of studies as it has been proposed to be associated with long-term implant success. The next step in this scientific development is to focus on the in situ fatigue procedure of two-component dental implants. Therefore, an apparatus has been developed which is optimized for the in situ fatigue analysis of dental implants. This report demonstrates both the capability of in situ radioscopy and microtomography at the ID19 beamline for the study of cyclic deformation in dental implants. The first results show that it is possible to visualize fatigue loading of dental implants in real-time radioscopy in addition to the in situ fatigue tomography. For the latter, in situ microtomography is applied during the cyclic loading cycles in order to visualize the opening of the IAC microgap. These results concur with previous ex situ studies on similar systems. The setup allows for easily increasing the bending force, to simulate different chewing situations, and is, therefore, a versatile tool for examining the fatigue processes of dental implants and possibly other specimens.

Contribution

P. Stahlhut
K. Dremel
J. Dittmann
J. Engel
Simon Zabler
A. Hoelzing
R. Hanke

First results on laboratory nano-CT with a needle reflection target and an adapted toolchain.

In: Developments in X-Ray Tomography X. (SPIE Proceedings) pg. 99670I

Eds.:
S. Stock
B. Müller
G. Wang

SPIE

(2016)

DOI: 10.1117/12.2240561

Journal article

A. Detterbeck
M. Hofmeister
D. Haddad
D. Weber
M. Schmid
A. Hölzing
Simon Zabler
E. Hofmann
K.-H. Hiller
P. Jakob
J. Engel
Jochen Hiller
U. Hirschenfelder

Determination of the mesio-distal tooth width via 3D imaging techniques with and without ionizing radiation: CBCT, MSCT, and μCT versus MRI.

In: European Journal of Orthodontics vol. 39 pg. 310-319

(2016)

DOI: 10.1093/ejo/cjw047

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Objective: The purpose of this study was to estimate the feasibility and accuracy of mesio-distal width measurements with magnetic resonance imaging (MRI) in comparison to conventional 3D imaging techniques [multi-slice CT (MSCT), cone-beam CT (CBCT), and µCT]. The measured values of the tooth widths were compared to each other to estimate the amount of radiation necessary to enable orthodontic diagnostics. Material and Methods: Two pig skulls were measured with MSCT, CBCT, µCT, and MRI. Three different judges were asked to determine the mesio-distal tooth width of 14 teeth in 2D tomographic images and in 3D segmented images via a virtual ruler in every imaging dataset. Results: Approximately 19% (27/140) of all test points in 2D tomographic slice images and 12% (17/140) of the test points in 3D segmented images showed a significant difference (P ≤ 0.05). The largest significant difference was 1.6mm (P < 0.001). There were fewer significant differences in the measurement of the tooth germs than in erupted teeth. Conclusions: Measurement of tooth width by MRI seems to be clinically equivalent to the conventional techniques (CBCT and MSCT). Tooth germs are better illustrated than erupted teeth on MRI. Three-dimensional segmented images offer only a slight advantage over 2D tomographic slice images. MRI, which avoids radiation, is particularly appealing in adolescents if these data can be corroborated in further studies.

Contribution

C. Fella
A. Balles
W. Wiest
Simon Zabler
R. Hanke

Laboratory source based full-field x-ray microscopy at 9 keV.

In: XRM 2014: Proceedings of the 12th International Conference on X-Ray Microscopy. (AIP conference proceedings) pg. 020025

AIP Publishing LLC

(2016)

DOI: 10.1063/1.4937519

Contribution

J. Dittmann
Simon Zabler
R. Hanke

Nested tomography: Application to direct ellipsoid reconstruction in anisotropic darkfield tomography.

In: 4th International Conference on X-ray and Neutron Phase Imaging with Gratings (XNPIG) 2017. pg. 49-50

(2017)

Contribution

Simon Zabler
A. Balles
J. Dittmann
C. Fella
R. Hanke

Quantitative phase contrast and X-ray scattering micro-tomography with the 9.2 keV liquid metal jet anode: applications on materials and life science.

In: Developments in X-Ray Tomography XI. pg. 8

Eds.:
B. Müller
G. Wang

SPIE

(2017)

DOI: 10.1117/12.2275889

Journal article

J. Dittmann
A. Balles
Simon Zabler

Optimization Based Evaluation of Grating Interferometric Phase Stepping Series and Analysis of Mechanical Setup Instabilities.

In: Journal of Imaging vol. 4 pg. 77

(2018)

DOI: 10.3390/jimaging4060077

show abstract

first_page settings Order Article Reprints Open AccessArticle Optimization Based Evaluation of Grating Interferometric Phase Stepping Series and Analysis of Mechanical Setup Instabilities by Jonas Dittmann 1,* [ORCID] , Andreas Balles 1 and Simon Zabler 1,2 1 Lehrstuhl für Röntgenmikroskopie, Universität Würzburg, Josef-Martin-Weg 63, 97074 Würzburg, Germany 2 Fraunhofer EZRT, NCTS Group Würzburg, Josef-Martin-Weg 63, 97074 Würzburg, Germany * Author to whom correspondence should be addressed. J. Imaging 2018, 4(6), 77; https://doi.org/10.3390/jimaging4060077 [In Citavi anzeigen] Submission received: 30 April 2018 / Revised: 30 May 2018 / Accepted: 4 June 2018 / Published: 7 June 2018 (This article belongs to the Special Issue Phase-Contrast and Dark-Field Imaging) Download keyboard_arrow_down Browse Figures Versions Notes Abstract The diffraction contrast modalities accessible by X-ray grating interferometers are not imaged directly but have to be inferred from sine-like signal variations occurring in a series of images acquired at varying relative positions of the interferometer’s gratings. The absolute spatial translations involved in the acquisition of these phase stepping series usually lie in the range of only a few hundred nanometers, wherefore positioning errors as small as 10 nm will already translate into signal uncertainties of 1–10% in the final images if not accounted for. Classically, the relative grating positions in the phase stepping series are considered input parameters to the analysis and are, for the Fast Fourier Transform that is typically employed, required to be equidistantly distributed over multiples of the gratings’ period. In the following, a fast converging optimization scheme is presented simultaneously determining the phase stepping curves’ parameters as well as the actually performed motions of the stepped grating, including also erroneous rotational motions which are commonly neglected. While the correction of solely the translational errors along the stepping direction is found to be sufficient with regard to the reduction of image artifacts, the possibility to also detect minute rotations about all axes proves to be a valuable tool for system calibration and monitoring. The simplicity of the provided algorithm, in particular when only considering translational errors, makes it well suitable as a standard evaluation procedure also for large image series.

Journal article

A. Youssef
A. Hrynevich
L. Fladeland
A. Balles
J. Groll
P. Dalton
Simon Zabler

The Impact of Melt Electrowritten Scaffold Design on Porosity Determined by X-Ray Microtomography.

In: Tissue Engineering. Part C, Methods vol. 25 pg. 367-379

(2019)

DOI: 10.1089/ten.tec.2018.0373

show abstract

Melt electrowriting is an AM technology that bridges the gap between solution electrospinning and melt microextrusion technologies. It can be applied to biomaterials and tissue engineering by making a spectrum of scaffolds with various laydown patterns at dimensions not previously studied. Using submicrometer X-ray tomography, a "fingerprint" of porosity for such scaffolds can be obtained and used as an important measure for quality control, to ensure that the scaffold fabricated is the one designed and allows the selection of specific scaffolds based on desired porosities.

Journal article

P. Vogel
J. Markert
M. Rückert
S. Herz
B. Keßler
K. Dremel
D. Althoff
M. Weber
T. Buzug
T. Bley
W. Kullmann
R. Hanke
Simon Zabler
V. Behr

Magnetic Particle Imaging meets Computed Tomography: first simultaneous imaging.

In: Scientific Reports (Nature Publishing Group) vol. 9 pg. 12627

02.09.2019 (2019)

DOI: 10.1038/s41598-019-48960-1

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Magnetic Particle Imaging (MPI) is a promising new tomographic modality for fast as well as three-dimensional visualization of magnetic material. For anatomical or structural information an additional imaging modality such as computed tomography (CT) is required. In this paper, the first hybrid MPI-CT scanner for multimodal imaging providing simultaneous data acquisition is presented.

Journal article

Peter Hornberger
A. Sigl
Jochen Hiller
Simon Zabler

Kleiner als ein Mikrometer: Entwicklung einer kompakten, hochauflösenden 3D-Röntgen-CT für die Materialanalyse.

In: VDI-Z (Sonderteil Additive Fertigung) pg. 52 ff.

(2019)

Contribution

T. Flügge
Simon Zabler
J. Hövener
U. Ludwig
K. Nelson
W. Semper-Hogg

Computerized Tomography for Craniomaxillofacial Dental Implantology.

In: Craniomaxillofacial Reconstructive and Corrective Bone Surgery. pg. 219-229

Eds.:
R. Schmelzeisen
A. Greenberg

Springer New York New York, NY

(2019)

DOI: 10.1007/978-1-4939-1529-3_18

Journal article

J. Graetz
A. Balles
R. Hanke
Simon Zabler

Review and experimental verification of x-ray dark-field signal interpretations with respect to quantitative isotropic and anisotropic dark-field computed tomography.

In: Physics in Medicine and Biology vol. 65 pg. 235017

27.11.2020 (2020)

DOI: 10.1088/1361-6560/abb7c6

show abstract

Talbot(-Lau) interferometric x-ray and neutron dark-field imaging has, over the past decade, gained substantial interest for its ability to provide insights into a sample's microstructure below the imaging resolution by means of ultra small angle scattering effects. Quantitative interpretations of such images depend on models of the signal origination process that relate the observable image contrast to underlying physical processes. A review of such models is given here and their relation to the wave optical derivations by Yashiro et al and Lynch et al as well as to small angle scattering is discussed. Fresnel scaling is introduced to explain the characteristic distance dependence observed in cone beam geometries. Moreover, a model describing the anisotropic signals of fibrous objects is derived. The Yashiro-Lynch model is experimentally verified both in radiographic and tomographic imaging in a monochromatic synchrotron setting, considering both the effects of material and positional dependence of the resulting dark-field contrast. The effect of varying sample-detector distance on the dark-field signal is shown to be non-negligible for tomographic imaging, yet can be largely compensated for by symmetric acquisition trajectories. The derived orientation dependence of the dark-field contrast of fibrous materials both with respect to variations in autocorrelation width and scattering cross section is experimentally validated using carbon fiber reinforced rods.

Journal article

Simon Zabler
M. Ullherr
C. Fella
R. Schielein
O. Focke
B. Zeller-Plumhoff
et al.

Comparing image quality in phase contrast sub μ X-ray tomography—A round-robin study.

In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment vol. 951 pg. 162992

(2020)

DOI: 10.1016/j.nima.2019.162992

show abstract

How to evaluate and compare image quality from different sub-micrometer (sub) CT scans? A simple test phantom made of polymer microbeads is used for recording projection images as well as 13 CT scans in a number of commercial and non-commercial scanners. From the resulting CT images, signal and noise power spectra are modelled for estimating volume signal-to-noise ratios (3D SNR spectra). Using the same CT images, a time- and shape-independent transfer function (MTF) is computed for each scan, including phase contrast effects and image blur (MTFblur). The SNR spectra and MTF of the CT scans are compared to 2D SNR spectra of the projection images. In contrary to 2D SNR, volume SNR can be normalized with respect to the object’s power spectrum, yielding detection effectiveness (DE) a new measure which reveals how technical differences as well as operator-choices strongly influence scan quality for a given measurement time. Using DE, both source-based and detector-based sub CT scanners can be studied and their scan quality can be compared. Future application of this work requires a particular scan acquisition scheme which will allow for measuring 3D signal-to-noise ratios, making the model fit for 3D noise power spectra obsolete.

Journal article

J. Graetz
J. Dombrowski
A. Eggert
A. Rack
U. Kulozik
J. Hinrichs
R. Hanke
Simon Zabler

Synchrotron micro-CT for studying coarsening in milk protein-stabilized foams in situ.

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects vol. 601 pg. 124832

(2020)

DOI: 10.1016/j.colsurfa.2020.124832

show abstract

Motivation Foam coarsening, i.e., the ripening of bubbles, constitutes a principal aging processes that links the microscopic, chemical composition of a foam with its macroscopic stability and texture. While the effects of chemical composition on macroscopic appearance are well studied, the actual three-dimensional bubble ripening remained quasi-inaccessible due to a lack of experimental techniques. Approach Using high-speed synchrotron micro computed tomography, the influence of pH on the coarsening of milk protein foams is studied in situ, individually tracking the ripening of thousands of bubbles in order to characterize the inter-bubble gas diffusion by fitting theoretical models on foam coarsening. Findings In all experiments the inter-bubble gas diffusion of milk protein-stabilized foams depend on pH. Despite having much different initial size distributions the coarsening kinetics of the foams are highly reproducible. A strong correlation between kinetic parameters describing coarsening and foam stability is observed, whereby faster coarsening occurs for less stable foams. Moreover, specific cases of high stability despite high diffusion rates could be observed for beta-lactoglobulin. These observations correlate with known changes in the macro-molecular configurations of the protein which result in different surface coverage of the liquid lamellae. These findings are first evidence of a likely microscopic-mesoscopic relationship in liquid foam chemistry.

Journal article

Simon Zabler
M. Maisl
Peter Hornberger
Jochen Hiller
C. Fella
R. Hanke

X-ray imaging and computed tomography for engineering applications. Röntgenbildgebung und Computertomografie für technische Anwendungen.

In: tm - Technisches Messen vol. 87 pg. 211-226

(2020)

DOI: 10.1515/teme-2019-0151

show abstract

After an incremental development which took place over four decades, X-ray imaging has become an important tool for non-destructive testing and evaluation. Computed Tomography (CT) in particular beholds the power of determining the location of flaws and inclusions (e. g. in castings and composites) in three-dimensional object coordinates. Therefore, and thanks to a speed-up of the measurement, CT is now routinely considered for in-line inspection of electronics, castings and composites. When precision and not speed is important, Micro-CT (μCT) can be employed for Dimensional Measurements (DM, e. g. quality assurance and shape verification), as well as for in situ testing, and for characterizing micro-structures in metals and composites. Using appropriate image processing and analysis μCT can determine the local fibre orientation in composites, the granular morphology of battery cathodes or the inter-connectivity of certain phases in casting alloys. Today, the large variety of X-ray instruments and methods poses an application problem which requires experience and a lot of knowledge for deciding which technique applies best to the task at hand. Application-specific guidelines exist for X-ray radiography testing (RT) only, whereas standardization has been applied to CT, unfortunately leaving out high resolution subμ CT, and nano-CT. For the latter exist an equally high number of NDT applications, however these instruments still necessitate a profound expertise. The task is to identify key industrial applications and push CT from system standardization to application specific automation.

Journal article

F. Lutter
P. Stahlhut
K. Dremel
Simon Zabler
J. Fell
H.-G. Herrmann
R. Hanke

Combining X-ray Nano Tomography with focused ion beam serial section imaging — Application of correlative tomography to integrated circuits.

In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms vol. 500-501 pg. 10-17

(2021)

DOI: 10.1016/j.nimb.2021.05.006

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In this research we show the combination of two sub-micrometer imaging techniques, namely focused ion beam (FIB) and scanning electron microscope (SEM)-based X-ray nano tomography, on the exact same sample, a fragment of a central processing unit (CPU). Based on its three-dimensional structure, we compare the volumetric measurement results in terms of scanned volume, spatial resolution, visible details, and artifacts. For comparability reasons we limit the acquisition time to 24 h for both imaging modalities. By this comparison we evaluate the capability of our self-developed laboratory nano-computed tomography system (XRM-II nano-CT) as its performance and usability was increased by the recent upgrades. The nano-computed tomography (nano-CT) offers a 12 times larger scanned sample volume than the FIB tomography on the one hand, but a lower volumetric resolution combined with a factor of 5 lower sampling on the other. The main artifacts of the nano-CT are blurred structures caused by incomplete alignment during the reconstruction process, while in the FIB tomography curtain artifacts lead to distorted structures in the reconstructed volume. We give an outlook to combine the benefits of the two methods, where the nano-CT is used as a navigational scan for the FIB tomography to achieve the best resolution on a given part of a sample.

Contribution

Gabriel Herl
A. Maier
Simon Zabler

X-ray CT Data Completeness Condition for Sets of Arbitrary Projections.

In: 7th International Conference on Image Formation in X-Ray Computed Tomography (ICIFXCT 2022). pg. 23

Eds.:
J. Stayman

SPIE, The International Society for Optics and Photonics

(2022)

DOI: 10.1117/12.2646435

Journal article

V. Haag
K. Dremel
Simon Zabler

Volumetric imaging by micro computed tomography: a suitable tool for wood identification of charcoal.

In: IAWA Journal vol. 44 pg. 210-224

(2022)

DOI: 10.1163/22941932-bja10106

show abstract

The present study focuses on the application of state-of-the-art μCT, by using a sub-micrometre CT scanner as a tool for wood identification. Charcoal was chosen as a subject for this case study. The reason for choosing charcoal is based on economic as well as technical issues. Parallel to conventional wood anatomy, various promising approaches to identification are currently being developed worldwide in order to simplify the identification of processed wood. However, due to the carbonization process, such approaches are not applicable to charcoal. In view of the rapid development of μCT technology, it was decided to examine the extent to which wood anatomical studies can be supported and improved by modern μCT technology. About 17% of the annually harvested wood worldwide is converted to charcoal (FAO 2017), and the charcoal trade is one of the least controlled/monitored segments of the European timber market. Although charcoal has a significant market share of wood-based products, it is still not yet covered by any trade regulation, e.g. the European Timber Regulations (EUTR), (EU) No995/2010. For the present study, different wood types and the anatomical fine structural features were measured and displayed at different magnifications to visualize the performance of state-of-the-art μCT standards. Three different charcoal assortments were examined, and the results were checked against the given declarations of contents. The aim of this work is to evaluate the potential of the μCT technique in the field of wood identification and to assess its use for the regulatory control of charcoal and other wood products in the international timber trade. The results are encouraging and lead to the conclusion that the application of the μCT technique in the field of wood identification can be classified as very promising for the future.

Journal article

T. Straub
J. Fell
Simon Zabler
T. Gustmann
H. Korn
S. Fischer

Characterization of Filigree Additively Manufactured NiTi Structures Using Micro Tomography and Micromechanical Testing for Metamaterial Material Models.

In: Materials vol. 16

10.01.2023 (2023)

DOI: 10.3390/ma16020676

show abstract

This study focuses on the influence of additive manufacturing process strategies on the specimen geometry, porosity, microstructure and mechanical properties as well as their impacts on the design of metamaterials. Filigree additively manufactured NiTi specimens with diameters between 180 and 350 µm and a nominal composition of Ni50.9Ti49.1 (at %) were processed by laser powder bed fusion in a first step. Secondly, they structures were characterized by optical and electron microscopy as well as micro tomography to investigate the interrelations between the process parameters, specimen diameters and microstructure. Each specimen was finally tested in a micro tensile machine to acquire the mechanical performance. The process strategy had, besides the resulting specimen diameter, an impact on the microstructure (grain size) without negatively influencing its quality (porosity). All specimens revealed a superelastic response while the critical martensitic phase transition stress decreased with the applied vector length. As a conclusion, and since the design of programmable metamaterials relies on the accuracy of FEM simulations, precise and resource-efficient testing of filigree and complex structures remains an important part of creating a new type of metamaterials with locally adjusted material behavior.

Journal article

J. Fell
C. Pauly
M. Maisl
Simon Zabler
F. Mücklich
H.-G. Hermann

Three-dimensional imaging of microstructural evolution in SEM-based nano-CT.

In: Tomography of Materials and Structures vol. 2 pg. 100009

(2023)

DOI: 10.1016/j.tmater.2023.100009

show abstract

Scanning electron microscopy (SEM) is a powerful and versatile technique for materials characterization and present in many laboratories. The integration of an X-ray target holder and detector allows expanding the modalities of SEM by X-ray imaging. These little hardware adaptations enable radiography or X-ray computed tomography (CT) to gain three-dimensional (3D) information about a sample to be investigated. Since SEM-based CT is a non-destructive technique, the method can also image time-dependent changes in microstructure. Presented is the ability of SEM-based nano-CT to image the microstructural evolution of an aluminum-germanium (AlGe32) alloy as a result of annealing. First, the non-destructive CT method is used for an overview scan to identify a hidden region of interest (ROI) in the sample volume at low resolution. The following FIB target preparation reveals the microstructure, which is stepwise annealed and investigated with SEM-based nano-CT at high resolution afterwards. The resulting reconstructed volumes gained from the laboratory-based system are visualized in 3D and show the morphology changes of microstructure. Quantitative analysis reveals grain coarsening and the formation of precipitations in the size of 300–1000 nm. These time-dependent processes are additionally correlated with hardness measurements of the Al alloy.

Contribution

Simon Rettenberger
Gabriel Herl
Peter Landstorfer
Simon Zabler

Multi-Source-CT for inline inspection of extruded profiles.

In: Proceedings of the 12th International Conference on Industrial Computed Tomography (iCT2023). pg. 1-9

(2023)

Journal article

Martin Leipert
Gabriel Herl
J. Stebani
Simon Zabler
A. Maier

Three Step Volumetric Segmentation for Automated Shoe Fitting.

In: e-Journal of Nondestructive Testing (12th Conference on Industrial Computed Tomography (iCT) 2023, 27 Feb-2 Mar 2023; Fürth, Germany) vol. 28 pg. 1-10

(2023)

DOI: 10.58286/27736

show abstract

This work presents a three-step segmentation process based on Convolutional Neural Networks. The task is to identify the different parts of shoes from Computed Tomography scans of boxed pairs of shoes. The first step of the three-step algorithm uses a scaled-down volume image to separate the shoe material from its surroundings. The second step segments the shoe's inside volume, i.e. the space enclosed by shoe material. The third and last step splits the segmented shoe material into individual components: shoe upper material, outer and insole. The complete process employs CNNs derived from three-dimensional UNets. Residual SE UNet, Dense UNet, and Bottleneck Residual UNet are evaluated for the three steps. The architectures are modified for large receptive fields. The networks are trained and tested for each step separately and conjointly on CT scans comprising various shoe types. The test results inspire hope for using the process for automated segmentation and extraction of meshes from large batches of CT scans. In particular, the first step using a Residual SE UNet achieves an F1-score of 88.2 % for shoes and 58.9 % for the packing material. The second step segments the inside volume with an F1-score of 81.0 %. The third step segments the shoe into its components and achieves an F1-score for insole of 79.5 %, outer sole of 88.7 % and upper material of 81.3 %.

Contribution

Anton Weiss
Simon Wittl
Gabriel Herl
Simon Zabler

Simulated and experimental evaluation of the accuracy of twin robotic CT systems.

In: Proceedings of the 12th International Conference on Industrial Computed Tomography (iCT2023). pg. 1-10

(2023)

Contribution

Simon Wittl
Anton Weiss
Gabriel Herl
Simon Zabler

Keep Attention to the Mapping: Application of AI for Geometric X-Ray RoboCT Scan Calibration.

In: Proceedings of the 12th International Conference on Industrial Computed Tomography (iCT2023). pg. 1-7

(2023)

Journal article

J. Stebani
M. Blaimer
Simon Zabler
T. Neun
D. Pelt
K. Rak

Towards fully automated inner ear analysis with deep-learning-based joint segmentation and landmark detection framework.

In: Scientific Reports (Nature Publishing Group) vol. 13 pg. 19057

04.11.2023 (2023)

DOI: 10.1038/s41598-023-45466-9

show abstract

Automated analysis of the inner ear anatomy in radiological data instead of time-consuming manual assessment is a worthwhile goal that could facilitate preoperative planning and clinical research. We propose a framework encompassing joint semantic segmentation of the inner ear and anatomical landmark detection of helicotrema, oval and round window. A fully automated pipeline with a single, dual-headed volumetric 3D U-Net was implemented, trained and evaluated using manually labeled in-house datasets from cadaveric specimen ([Formula: see text]) and clinical practice ([Formula: see text]). The model robustness was further evaluated on three independent open-source datasets ([Formula: see text] scans) consisting of cadaveric specimen scans. For the in-house datasets, Dice scores of [Formula: see text], intersection-over-union scores of [Formula: see text] and average Hausdorff distances of [Formula: see text] and [Formula: see text] voxel units were achieved. The landmark localization task was performed automatically with an average localization error of [Formula: see text] voxel units. A robust, albeit reduced performance could be attained for the catalogue of three open-source datasets. Results of the ablation studies with 43 mono-parametric variations of the basal architecture and training protocol provided task-optimal parameters for both categories. Ablation studies against single-task variants of the basal architecture showed a clear performance benefit of coupling landmark localization with segmentation and a dataset-dependent performance impact on segmentation ability.

Contribution

J. Fell
F. Lutter
C. Pauly
M. Engstler
F. Han
R. Costa
Simon Zabler
M. Maisl
F. Mücklich
R. Hanke
H.-G. Hermann

Correlative microscopy using SEM based nano-CT.

In: X-Ray Nanoimaging: Instruments and Methods VI. pg. 9

Eds.:
B. Lai
A. Somogyi

SPIE

(2023)

DOI: 10.1117/12.2677235

Contribution

Martin Leipert
Gabriel Herl
M. Müller
J. Messkemper
Simon Zabler

Automated Shoe Metrology by X-Ray Computed Tomography.

In: Proceedings of 3DBODY.TECH 2023 - 14th International Conference and Exhibition on 3D Body Scanning and Processing Technologies.

Eds.:
N. DApuzzo

Hometrica Consulting - Dr. Nicola D'Apuzzo Ascona, Switzerland

(2023)

DOI: 10.15221/23.48

Journal article

Martin Leipert
Gabriel Herl
Simon Zabler
A. Maier

Volumetric Instance Detection for Overlapping Shoes in Computed Tomography.

In: e-Journal of Nondestructive Testing (13th Conference on Industrial Computed Tomography (iCT) 2024, 6-9 Feb 2024; School of Engineering, Wals Campus, Austria) vol. 29

(2024)

DOI: 10.58286/29229

show abstract

This work presents an implementation of the Fully Convolutional One-Stage Object Detection (FCOS) object detector for anchorfree detection in volumetric Computed Tomography (CT) data. We test the implementation on a one-class dataset of shoes in closed packages, which is especially challenging to segment due to bounding boxes that overlap up to around 60 %. This complex dataset is tackled with a problem-specific loss function and loss computation. With a Residual-Squeeze-and-Excitation-Network, a lightweight backend is used, and with this, we reach a large receptive field of 2563 voxels. Our algorithm finds instances in volumetric data: for the detection, we reach an average Intersection over Union (IoU) of the predicted bounding box with the ground truth of 0.580 and an Average Precision (AP@IoU=0.5 ) of 84.4% at the best setting. With these results, we can proceed towards instance detection and voxel-wise instance segmentation in volumetric CT data.

Journal article

F. Sukowski
Daniel Rauch
R. Schielein
T. Schön
A. Waldyra
M. Fries
A. Maier
L.-S. Schneider
Gabriel Herl
Simon Wittl
Simon Zabler
et al.

SmartCT - Development of AI based methods for automation of RoboCT scan procedures.

In: e-Journal of Nondestructive Testing (13th Conference on Industrial Computed Tomography (iCT) 2024, 6-9 Feb 2024; School of Engineering, Wals Campus, Austria) vol. 29

(2024)

DOI: 10.58286/29232

show abstract

The SmartCT system consists of AI based methods that assist users of robot-based CT systems (RoboCT) to digitalize industrial parts of almost arbitrary size and geometrical complexity with a high degree of automation. Due to the high number of degrees of freedom and thus complexity, RoboCT scan procedures are difficult to parametrize with respect to collision safety and image quality. The SmartCT assist functions help users to perform measurements quickly and safely while using advanced algorithms for geometrical image correction and 3D-CT volume reconstruction.

Journal article

Simon Wittl
Anton Weiss
Gabriel Herl
Simon Zabler
P. Dewailly
R. Le Goff

Unveiling the Full Picture: Advanced Scanning Procedure for Complete Large Component Scans via Twin Robotic Computed Tomography.

In: e-Journal of Nondestructive Testing (13th Conference on Industrial Computed Tomography (iCT) 2024, 6-9 Feb 2024; School of Engineering, Wals Campus, Austria) vol. 29

(2024)

DOI: 10.58286/29260

show abstract

Twin robotic computed tomography (RoboCT) offers a high degree of flexibility. RoboCT systems are commonly used for either flexible 2D inspection of large areas or 3D inspection of small areas in large objects. This study introduces a workflow to perform a full CT scan of large objects that exceed the field of view with the help of RoboCT. To achieve this, we virtually enlarges the detector's size to enable reconstruction of larger objects or large region of interests and use projection stitching with a multi-angle Xray projection registration method.

Journal article

B. Spahn
J. Voelker
F.-T. Müller-Graff
J. Engert
D. Bauer
A. Kurz
R. Hagen
T. Neun
Simon Zabler
K. Rak

Development of an Algorithm for Correct Placement of the Basal Electrode Contact in the Context of Anatomy-Based Cochlear Implantation: A Proof of Concept.

In: Audiology & Neurotology vol. 29 pg. 398-407

13.03.2024 (2024)

DOI: 10.1159/000537933

show abstract

BACKGROUND Correct individual tonotopic frequency stimulation of the cochlea plays an important role in the further development of anatomy-based cochlear implantation. In this context, frequency-specific fitting of the basal electrode contact with a normal insertion depth can be difficult since it is often placed in a frequency range higher than 10 kHz, and current audio processors only stimulate for frequencies up to 8.5 kHz due to microphone characteristics. This results in a mismatch of the high frequencies. Therefore, this study represents a proof of concept for a tonotopic correct insertion and aims to develop an algorithm for a placement of the basal electrode below 8.5 kHz in an experimental setting. METHODS Pre- and postoperative flat-panel volume CT scans with secondary reconstructions were performed on 10 human temporal bone specimens. The desired frequency location for the most basal electrode contact was set at 8.25 kHz. The distance from the round window to the position where the basal electrode contact was intended to be located was calculated preoperatively using 3D-curved multiplanar reconstruction and a newly developed mathematical approach. A specially designed cochlear implant electrode array with customized markers imprinted on the silicone of the electrode array was inserted in all specimens based on the individually calculated insertion depths. All postoperative measurements were additionally validated using otological planning software. RESULTS Positioning of the basal electrode contact was reached with only a small mean deviation of 37 ± 399 Hz and 0.06 ± 0.37 mm from the planned frequency of 8.25 kHz. The mean rotation angle up to the basal electrode contact was 51 ± 5°. In addition, the inserted electrode array adequately covered the apical regions of the cochleae. CONCLUSION Using this algorithm, it was possible to position the basal electrode array contact in an area of the cochlea that could be correctly stimulated by the existing speech processors in the context of tonotopic correct fitting.

Journal article

Daniel Rauch
Simon Wittl
Simon Zabler

rosct: A distributed, scriptable CT control framework for iterative research-oriented method and application development.

In: e-Journal of Nondestructive Testing (13th Conference on Industrial Computed Tomography (iCT) 2024, 6-9 Feb 2024; School of Engineering, Wals Campus, Austria) vol. 29

(2024)

DOI: 10.58286/29247

show abstract

Industrial Computed Tomography (CT) scan control software must meet the highest standards of reliability, performance, and efficiency, which is why these criteria also form the main focus in their system design. Current systems excel when utilized for the specific task and workflow for which they were originally designed by the manufacturer. However, during early development of new CT scanners, research-oriented method development and during implementation of custom inspection tasks, different requirements can be observed. Due to the iterative, dynamic approach in these areas, the control software must also be flexible, adaptable, and easily automatable while still being user friendly. To reduce iteration times further, the native integration of common research-oriented development toolsets and 3rd party ecosystem are key. In addition, CT as technology is evolving in regards of actorics (e.g., twin robotic CT systems) and model driven design (e.g., digital twins), all not fully supported by most current control platforms, which hinders development speed and adaptation. To summarize, there is a noticeable gap between the requirements of researchers and development departments regarding the capabilities of the existing CT systems. This discrepancy motivates the need to explore and develop CT control systems that are open, easily adaptable, and extendable. These insights are put into practice with the novel rosct CT control framework, which is presented in this paper.

Journal article

M. Diez
N. Saeidnezhad
P. Tafforeau
Simon Zabler

Benefits of front coating crystalline scintillator screens for phase-contrast synchrotron micro-tomography.

In: Optics Express vol. 32 pg. 41790-41803

(2024)

DOI: 10.1364/OE.534383

show abstract

Transparent crystalline scintillators such as cerium-doped YAG or LuAG are widely used in X-ray imaging for the indirect detection of X-rays. The application of reflective coatings on the front side to improve the optical gain is common practice for flat panel detectors with CsI or Gd2O2S powder scintillators but still largely unknown for crystalline scintillators such as LuAG. This work shows experimentally and quantitatively how a black and reflective coating on the X-ray side of a 2 mm LuAG:Ce scintillator improves the image quality compared to a 2 mm LuAG:Ce scintillator without a coating. The measurements have been done for two different distances, with 2 m and 29.7 m on the BM18 beamline of the European Synchrotron. The Modulation Transfer Function (MTF) and the Signal-to-Noise-Ratio (SNR2) power spectrum as well as contrast-to-noise ratio are used for comparing image quality. Propagation-based phase contrast strongly enhances the SNR2 amplitudes (gain ≈10 from 2 m to 29.7 m object-detector distance) of the raw images' spectrum independent of the scintillator coating. For both detector positions, the reflective coating is able to raise SNR2 by up to 80% through the improved optical gain, while black coating does the opposite (decrease SNR2 by 20%) with respect to no coating. With the tested optical setups, changes in MTF /sharpness between the coatings are minor. Comparing CNR2 in CT scans of a multi-material sample, in this case an electric motor, we observe the reflective coating yielding better material contrast for plastic and air. Application and effect of Wiener-deconvolution, along with Paganin-type phase retrieval, are also discussed in the context of CT image quality.

Journal article

J. Vijayakumar
H. Dejea
A. Mirone
C. Muzelle
J. Meyer
C. Jarnias
K. Dollman
Simon Zabler
L. Paolasini
A. Bellier
B. Cordonnier
V. Fernandez
P. Tafforeau

Multiresolution Phase-Contrast Tomography on BM18, a New Beamline at the European Synchrotron Radiation Facility.

In: Synchrotron Radiation News vol. 37 pg. 16-25

(2024)

DOI: 10.1080/08940886.2024.2414724

show abstract

X-ray micro computed tomography (XµCT) is a non-invasive imaging technique used in various fields of science and engineering. Digital volumes generated with this technique have a fixed resolution linked to the source properties (such as source size, flux), the detector characteristics (i.e., number of pixels, pixel size) and magnification (using X-rays in conical geometry or visible light optics in parallel beam geometry). Imaging the same object at different magnification provides a set of nested datasets, offering a hierarchical view with multiple resolutions. Such multiscale characterization can enable measuring large objects at low resolution and to focus on specific regions at higher resolution, typically using local tomography. It makes it possible to easily correlate macroscopic and microscopic information without resorting to a full high-resolution characterization of the object which can be quite challenging. In the case of synchrotron radiation X-ray micro computed tomography (SRµCT), the magnification is typically carried out at the detector level, due to the quasi-parallel beam geometry. These indirect detector setups consist of a scintillator, a set of visible light optical devices, and a visible light imaging sensor such as a Couple Charged Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS). Therefore, hierarchical capabilities are constrained by the set of available detectors and the possibility to swap them during an experiment, together with suitable tunability of the beam properties. The BM18 beamline of the European Synchrotron Radiation Facility - Extremely Brilliant Source (ESRF - EBS, Grenoble, France) was developed to streamline multiscale propagation phase contrast SRµCT, and is currently suitable for samples with thickness/diameter from few mm up to ca. 30 cm. The beamline was commissioned in late 2021 and has been welcoming users ever since 2022. In this report we present the beamline aspects that play an important role towards achieving the multiresolution phase-contrast imaging modality. Finally, we present examples of different experiments performed in natural and cultural heritage, geosciences, material sciences (including industrial applications) and biomedical research.

Journal article

J. Angermair
G. Iglhaut
K. Meyenberg
W. Wiest
A. Rack
Simon Zabler
T. Fretwurst
K. Nelson
F. Kernen

In vitro assessment of internal implant-abutment connections with different cone angles under static loading using synchrotron-based radiation.

In: BMC Oral Health vol. 24 pg. 396

28.03.2024 (2024)

DOI: 10.1186/s12903-024-04156-2

show abstract

BACKGROUND The stability of implant-abutment connection is crucial to minimize mechanical and biological complications. Therefore, an assessment of the microgap behavior and abutment displacement in different implant-abutment designs was performed. METHODS Four implant systems were tested, three with a conical implant-abutment connection based on friction fit and a cone angle < 12 ° (Medentika, Medentis, NobelActive) and a system with an angulated connection (< 40°) (Semados). In different static loading conditions (30 N - 90º, 100 N - 90º, 200 N - 30º) the microgap and abutment displacement was evaluated using synchrotron-based microtomography and phase-contrast radioscopy with numerical forward simulation of the optical Fresnel propagation yielding an accuracy down to 0.1 μm. RESULTS Microgaps were present in all implant systems prior to loading (0.15-9 μm). Values increased with mounting force and angle up to 40.5 μm at an off axis loading of 100 N in a 90° angle. CONCLUSIONS In contrast to the implant-abutment connection with a large cone angle (45°), the conical connections based on a friction fit (small cone angles with < 12°) demonstrated an abutment displacement which resulted in a deformation of the outer implant wall. The design of the implant-abutment connection seems to be crucial for the force distribution on the implant wall which might influence peri-implant bone stability.

Journal article

J. Glinz
B. Plank
J. Gutekunst
M. Scheerer
Simon Zabler
J. Kastner
S. Senck

A comparison of X-ray attenuation, differential phase, and dark-field contrast imaging for the detection of porosity in carbon fiber reinforced cyanate ester.

In: NDT & E International vol. 147 pg. 103194

(2024)

DOI: 10.1016/j.ndteint.2024.103194

show abstract

In this work we explore the capabilities of Talbot-Lau grating interferometry (TLGI) radiography for the inspection of porosity in structural specimens of cyanate ester carbon fiber reinforced polymer. The influence of system resolution and varying specimen thicknesses on mean values and standard deviations (STDV) in all three image modalities acquired by TLGI are addressed. Results show that mean absorption contrast (AC) values are highly affected by specimen thickness and strong negative correlation (r ≤ −0.8) is found only after correction via preliminary thickness measurements. Although dark-field contrast (DFC) is affected by changes in specimen thickness as well, the signal can be corrected by normalization with the inherently available AC. Consequently, strong positive correlation with porosity was found both in high- and low-resolution imaging (r = 0.83 and 0.71 respectively). Without the need for high image resolution or thickness measurements, the normalized DFC is a promising option for large field of view inspections. Investigations of STDV revealed strong positive correlations between porosity and AC STDV as well as differential phase contrast (DPC) STDV (r = 0.95 and 0.92 respectively) but high image resolution is required. Furthermore, results suggest increased robustness against variations in specimen thickness of AC and DPC STDV analyses.

projects

RoboCT

labs

TC Plattling, C010, L009

core competencies

Computed Tomography, Imaging, Image-and Signal-Processing, Physics, Materials

Forschungs- und Lehrgebiete

Computed Tomography, Robotics, Measurement Science, Mathematics

Vita

since 2021 Professor for Imaging Methods centered around Computed Tomography TH Deggendorf 2018–2021 Deputy head of the Magnetic Resonance- and X-ray department MRB, Fraunhofer IIS 2011–2018 Habilitation, Chair of X-ray Microscopy LRM, Julius-Maximilians-University Würzburg 2015–2018 Head of Fraunhofer project group NanoCT Systems NCTS, Fraunhofer IIS, Würzburg 2011–2015 Head of research and education, Chair of X-ray Microscopy LRM, University Würzburg 2009–2011 Assistant Professor at the department of Materials Engineering, TU Berlin 2008–2009 Postdoc, Max-Planck Institute of Colloids and Interfaces (biomaterials), Potsdam 2004–2007 Doctorate, Technical University (TU) Berlin, Doctor of natural sciences 2003–2004 European sales engineer for Laser Measurement Systems, Polytec GmbH, Waldbronn 2001–2002 Diplôme d’Etudes Approfondies (first doctorate), Physique des Matériaux, Université Grenoble 2000–2002 Diplôme d’Ingénieur /Master, École Nationale Supérieure de Physique de Grenoble (ENSPG) 1997–2003 Diploma in Physics, University Karlsruhe (TH)