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Open Access
Abstract: Purpose: In dental offices, there is a trend replacing conventional silicone impressions and plaster cast models by imaging data of intraoral scanners to map the denture and surrounding tissues. The aim of the study is the analysis of the accuracy of selected commercially available scanners. The accuracy is considered as the main drawback in comparison to the conventional approach.
Approach: We evaluated the reproduction performance of five optical scanners by a direct comparison with high-resolution hard x-ray computed tomography data, all obtained from a polyetheretherketone model with similarity to a full-arch upper jaw.
Results: Using the software GOM Inspect (GOM GmbH, Braunschweig, Germany), we could classify the intraoral scanners into two groups. The more accurate instruments gave rise to the following precision values: 35 μm (TRIOS® 3, 3shape, Copenhagen, Denmark), 43 μm (CS 3600, Carestream, Atlanta, Georgia), and 46 μm (3M™ True Definition Scanner, 3M ESPE, St. Paul, Minnesota). The less precise systems yielded 93 μm (Medit i500, Medit corp., Seongbuk-gu, South Korea) and 97 μm (Emerald™, Planmeca Oy, Helsinki, Finland).
Conclusions: The selected scanners are suitable for single crowns, small bridges, and separate quadrants prostheses. Scanners based on triangulation are hardly appropriate for full-arch prostheses. Besides precision, however, the choice of the scanner depends on scanning time, intraoral-camera size, and the user’s learning curve. The developed protocol, which includes three-dimensional (3D) imaging and advanced computational tools for the registration with the design data, will be increasingly used in geometrical metrology by nondestructive procedures to perform dimensional measurements with micrometer precision and is capable for detailed 3D geometrical models reconstruction.
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May 2021
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19829, 20746]
Abstract: Hard x-ray tomography with Paganin's widespread single-distance phase retrieval filter improves the contrast-to-noise ratio (CNR) while reducing spatial resolution (SR). We demonstrate that a Gaussian filter provided larger CNR at high SR with interpretable density measurements for two medically relevant soft tissue samples. Paganin's filter produced larger CNR at low SR, though a priori assumptions were generally false and image quality gains diminish for CNR > 1. Therefore, simple absorption measurements of low-Z specimens combined with Gaussian filtering can provide improved image quality and model-independent density measurements compared to single-distance phase retrieval.
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Jan 2020
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19829]
Abstract: X-ray grating interferometry (XGI) is a phase-contrast imaging technique that allows for a quantitative measurement of the refractive index with high density resolution in a model-independent manner—i.e. without a priori knowledge of the specimen composition. However, the retrieval of the X-ray wavefront phase shift relies on the accurate measurement of the interference pattern phase shift, making XGI vulnerable to phase wrapping when the interference pattern phase shift, related to the derivative of the wavefront phase shift, is large. Standard procedure for avoiding phase wrapping involves submerging the specimen in a water bath to reduce the mismatch of the index of refraction at the boundaries, but this requires a top-down rotation stage and is susceptible to gas bubble formation inside the water bath. Our team has presented an algorithm to remove phase wrapping artifacts for cylindrically shaped specimens that is applied to the phase-retrieved sinogram. This algorithm models and replaces phase-wrapped data to prevent the spread of “cupping” artifacts due to the integration of the differential phase during reconstruction. We give a criterion for selecting the modeling parameters so that the resulting measurement of the index of refraction matches the results of measurements without phase wrapping. We also apply this technique to cases where phase wrapping occurs at multiple interfaces. This algorithm allows for XGI measurements without a water bath and top-down rotation stage at synchrotron and laboratory facilities, especially as sensitivity increases.
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Sep 2019
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I13-2-Diamond Manchester Imaging
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Christos
Bikis
,
Griffin
Rodgers
,
Hans
Deyhle
,
Peter
Thalmann
,
Alexander
Hipp
,
Felix
Beckmann
,
Timm
Weitkamp
,
Stamatios
Theocharis
,
Christoph
Rau
,
Georg
Schulz
,
Bert
Muller
Diamond Proposal Number(s):
[19829]
Open Access
Abstract: Advances in high-resolution hard X-ray computed tomography have led to the field of virtual histology to complement histopathological analyses. Phase-contrast modalities have been favored because, for soft tissues, the real part of the refractive index is orders of magnitude greater than the imaginary part. Nevertheless, absorption-contrast measurements of paraffin-embedded tissues have provided exceptionally high contrast combined with a submicron resolution. In this work, we present a quantitative comparison of phase tomography using synchrotron radiation-based X-ray double grating interferometry and conventional synchrotron radiation-based computed tomography in the context of histopathologically relevant paraffin-embedded human brain tissue. We determine the complex refractive index and compare the contrast-to-noise ratio (CNR) of each modality, accounting for the spatial resolution and optimizing the photon energy for absorption tomography. We demonstrate that the CNR in the phase modality is 1.6 times higher than the photon-energy optimized and spatial resolution-matched absorption measurements. We predict, however, that a further optimized phase tomography will provide a CNR gain of 4. This study seeks to boost the discussion of the relative merits of phase and absorption modalities in the context of paraffin-embedded tissues for virtual histology, highlighting the importance of optimization procedures for the two complementary modes and the trade-off between spatial and density resolution, not to mention the disparity in data acquisition and processing.
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Feb 2019
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[19829]
Open Access
Abstract: X-ray grating interferometry-based computed tomography is a phase contrast imaging technique that provides non-destructive, quantitative, and three-dimensional visualization with contrast superior to traditional absorption-based techniques, especially for materials primarily composed of low Z elements, such as biological tissues. However, it relies on measurements of the lateral shift of an interference pattern and is thus susceptible to so-called phase wrapping artifacts, which mainly occur at the sample-air interface. In this work, we present an algorithm for removal of such artifacts in the case of cylindrical samples and an experiment to verify its accuracy. The proposed algorithm is applied to the sinogram after phase retrieval and prior to reconstruction by finding sample edges with the absorption sinogram and replacing regions of the phase wrapped sinogram with modeled data. Our measurements show that the algorithm removes artifacts and produces more accurate δ values, as validated by measurements without phase wrapping. Our correction algorithm allows for measurements without submerging the sample in a water bath, simplifying the experimental setup and avoiding motion artifacts from gas bubbles.
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Aug 2018
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I13-2-Diamond Manchester Imaging
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Aug 2018
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[13210]
Open Access
Abstract: Visualizing the internal architecture of large soft tissue specimens within the laboratory environment in a label-free manner is challenging, as the conventional absorption-contrast tomography yields a poor contrast. In this communication, we present the integration of an X-ray double-grating interferometer (XDGI) into an advanced, commercially available micro computed tomography system nanotom® m with a transmission X-ray source and a micrometer-sized focal spot. The performance of the interferometer is demonstrated by comparing the registered three-dimensional images of a human knee joint sample in phase- and conventional absorption-contrast modes. XDGI provides enough contrast (1.094 ± 0.152) to identify the cartilage layer, which is not recognized in the conventional mode (0.287 ± 0.003). Consequently, the two modes are complementary, as the present XDGI set-up only reaches a spatial resolution of (73 ± 6) μm, whereas the true micrometer resolution in the absorption-contrast mode has been proven. By providing complimentary information, XDGI is especially a supportive quantitative method for imaging soft tissues and visualizing weak X-ray absorbing species in the direct neighborhood of stronger absorbing components at the microscopic level.
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Mar 2018
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I13-2-Diamond Manchester Imaging
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Marie-Christine
Zdora
,
Joan
Vila-Comamala
,
Georg
Schulz
,
Anna
Khimchenko
,
Alexander
Hipp
,
Andrew C.
Cook
,
Daniel
Dilg
,
Christian
David
,
Christian
Grünzweig
,
Christoph
Rau
,
Pierre
Thibault
,
Irene
Zanette
Diamond Proposal Number(s):
[13164]
Open Access
Abstract: The high-throughput 3D visualisation of biological specimens is essential for studying diseases and developmental disorders. It requires imaging methods that deliver high-contrast, high-resolution volumetric information at short sample preparation and acquisition times. Here we show that X-ray phase-contrast tomography using a single grating can provide a powerful alternative to commonly employed techniques, such as high-resolution episcopic microscopy (HREM). We present the phase tomography of a mouse embryo in paraffin obtained with an X-ray single-grating interferometer at I13-2 Beamline at Diamond Light Source and discuss the results in comparison with HREM measurements. The excellent contrast and quantitative density information achieved non-destructively and without staining using a simple, robust setup make X-ray single-grating interferometry an optimum candidate for high-throughput imaging of biological specimens as an alternative for existing methods like HREM.
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Jan 2017
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I13-2-Diamond Manchester Imaging
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Anna
Khimchenko
,
Georg
Schulz
,
Hans
Deyhle
,
Peter
Thalmann
,
Irene
Zanette
,
Marie-Christine
Zdora
,
Christos
Bikis
,
Alexander
Hipp
,
Simone E.
Hieber
,
Gabriel
Schweighauser
,
Jürgen
Hench
,
Bert
Müller
Abstract: X-ray imaging in absorption contrast mode is well established for hard tissue visualization. However, performance for lower density materials is limited due to a reduced contrast. Our aim is three-dimensional (3D) characterization of micro-morphology of human brain tissues down to (sub-)cellular resolution within a laboratory environment. Using the laboratory-based microtomography (μCT) system nanotom m (GE Sensing and Inspection Technologies GmbH, Wunstorf, Germany) and synchrotron radiation at the Diamond-Manchester Imaging Branchline I13-2 (Diamond Light Source, Didcot, UK), we have acquired 3D data with a resolution down to 0.45 μm for visualization of a human cerebellum specimen down to cellular level. We have shown that all selected modalities, namely laboratory-based absorption contrast micro-tomography (LBμCT), synchrotron radiation based in-line single distance phase contrast tomography (SDPR) and synchrotron radiation based single-grating interferometry (GI), can reach cellular resolution for tissue samples with a size in the mm-range. The results are discussed qualitatively in comparison to optical microscopy of haematoxylin and eosin (HE) stained sections. As phase contrast yields to a better data quality for soft tissues and in order to overcome restrictions of limited beamline access for phase contrast measurements, we have equipped the μCT system nanotom m with a double-grating phase contrast set-up. Preliminary experimental results of a knee sample consisting of a bony part and a cartilage demonstrate that phase contrast data exhibits better quality compared to absorption contrast. Currently, the set-up is under adjustment. It is expected that cellular resolution would also be achieved. The questions arise (1) what would be the quality gain of laboratory-based phase contrast in comparison to laboratory-based absorption contrast tomography and (2) could laboratory-based phase contrast data provide comparable results to synchrotron radiation based phase contrast data.
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Oct 2016
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I13-2-Diamond Manchester Imaging
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Open Access
Abstract: Brain tissue evaluation is essential for gaining in-depth insight into its diseases and disorders. Imaging the human brain in three dimensions has always been a challenge on the cell level. In vivo methods lack spatial resolution, and optical microscopy has a limited penetration depth. Herein, we show that hard X-ray phase tomography can visualise a volume of up to 43 mm3 of human post mortem or biopsy brain samples, by demonstrating the method on the cerebellum. We automatically identified 5,000 Purkinje cells with an error of less than 5% at their layer and determined the local surface density to 165 cells per mm2 on average. Moreover, we highlight that three-dimensional data allows for the segmentation of sub-cellular structures, including dendritic tree and Purkinje cell nucleoli, without dedicated staining. The method suggests that automatic cell feature quantification of human tissues is feasible in phase tomograms obtained with isotropic resolution in a label-free manner.
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Sep 2016
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