Phase-contrast X-ray tomography: Contrast mechanism and roles of phase retrieval

Wu, Xizeng; Liu, Hong; Yan, Amin

doi:10.1016/j.ejrad.2008.04.027

Cited by 34 publications

(33 citation statements)

References 12 publications

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“…tissue and air. Furthermore, µ Mixed (x) is an artifact related to the overall variations of µ Abs and µ PhC , which will hence lead to a distortion of the local structure of the imaged lung sample [45]. The estimation of the µ Recon (x) for tissue will therefore be slightly inaccurate [45].…”

Section: Imaging Modesmentioning

confidence: 99%

“…samples with a low Z, which are poor absorbers of X-rays [47]. Wu et al [45] estimated δ and β values for biological tissues, where it was further shown that δ is around 1000 times stronger than β in the X-ray range of 10-100 keV [48,49]. This also implies that the difference in terms of δ between two given tissues are larger, than the differences in β, thus suggesting that X-ray based PhC-imaging is more sensitive, than standard Abs-imaging [50,51,52,48,49,53] Figure 12: Illustration of the diffraction of X-rays for Absorption vs. propagation based imaging, for various sample-to-detector distances, z, where λ is the X-ray wavelength and d is the size of a sample structure orthogonally to the beam direction [47].…”

Section: Imaging Modesmentioning

confidence: 99%

“…where the imaginary part β is responsible for the attenuation of the sample, while as the term δ is the refractive index decrement related to the phase-shift of the incident X-rays interacting with the sample [45].…”

Section: Imaging Modesmentioning

confidence: 99%

“…Furthermore, in Paper I, it was demonstrated that by suppressing phase-effects, as done by using PhR, a more precise grey level thresholding of the slices can be performed. Wu et al [45] also stated that for more accurate characterization of tissue, the acquired projections should be used to reconstructed two different data sets, one based on only the linear attenuation coefficient of tissue, β and the other one based on the tissue refraction, δ. …”

Section: Imaging Modesmentioning

confidence: 99%

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Evaluation of the Dual-Modal usage of contrast agents by means of Synchrotron X-ray Computed Microtomography and Magnetic Resonance Imaging using Macrophages loaded with Barium Sulfate and Gadolinium Nanoparticles for Detection and Monitoring in Animal Disease Models

Larsson

2015

Linköping Studies in Science and Technology. Dissertations

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To My Family. A B S T R A C TTechnical improvements of imaging devices during the last two decades have led to the development of so called hybrid imaging modalities, containing at least two different imaging modalities in the same machine. Hybrid imaging allows the combination of multi-modal images and the extraction of both complementary and synergistic information, which is useful for more accurate and reliable diagnosis. Within this framework there was an increased need for multi-modal contrast agents. During the last decade development of multi-modal contrast agents have hence received further attention.Recent developments of X-ray based imaging techniques now also offers imaging in other regimes, than standard absorption based imaging, e.g. phase contrast imaging, which exploits the refraction and phase-shift of the incident X-ray beam at tissue-interfaces. It has been shown that phase contrast imaging is more sensitive than classical clinical radiography, especially in soft-tissue applications, such as mammography.This thesis focuses on evaluating the dual-modal Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) capabilities of contrast agents. For such purposes a gadolinium based contrast agent is of high interest, due to its paramagnetic properties, which while present inside a magnetic field will hence interact with the protons spins of water (in tissue and fat) and shorten their the T1 relaxation time, thereby creating a positive image contrast in MRI. Furthermore, the X-ray Mass Attenuation Coefficient (MAC) of gadolinium is relatively high, thus suggesting its potential use, also as a CT contrast agent.Gadolinium nanoparticles can be loaded into cells, such as macrophages, which offers the possibility to track cells inside entire organisms. In the first step the uptake of gadolinium nanoparticles inside cells was investigated, together with a test for toxicity. To show the potential of using gadolinium nanoparticle loaded macrophages for functional imaging of inflammation, an acute allergic airway inflammation mouse model (mimicking asthma in humans) was used and analyzed by in-situ synchrotron phase contrast CT. This animal model was chosen, since macrophages are one of the main effector cells in asthma, where especially their ability to migrate is of crucial interest, which up until now was not possible to study in-situ. v In the first step this approach was evaluated using macrophages loaded with a clinical contrast agent containing barium sulphate, since this agent is known to provide high contrast in CT. In the ultimate step a combination of both barium sulphate and gadolinium nanoparticle loaded macrophages was used in the same mouse model (mimicking human asthma) and analyzed by dual modal Synchrotron phase contrast CT and Micro Magnetic Resonance Imaging (µ-MRI).Complementary results in terms of the biodistribution of injected macrophages could only be obtained by the combination of both synchrotron phase contrast CT and µ-MRI, where the first modality allows a detailed local...

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Section: Imaging Modesmentioning

confidence: 99%

Section: Imaging Modesmentioning

confidence: 99%

Section: Imaging Modesmentioning

confidence: 99%

Section: Imaging Modesmentioning

confidence: 99%

See 2 more Smart Citations

Evaluation of the Dual-Modal usage of contrast agents by means of Synchrotron X-ray Computed Microtomography and Magnetic Resonance Imaging using Macrophages loaded with Barium Sulfate and Gadolinium Nanoparticles for Detection and Monitoring in Animal Disease Models

Larsson

2015

Linköping Studies in Science and Technology. Dissertations

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show abstract

“…1 [3,4]. Then, filtered back projection [5] is applied to these phase maps in order to recover the refractive index decrement during reconstruction.…”

Section: Introductionmentioning

confidence: 99%

Integrated approach to the data processing of four-dimensional datasets from phase-contrast x-ray tomography

Shahani¹,

Gulsoy²,

Gibbs³

et al. 2014

Opt. Express

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Phase contrast X-ray tomography (PCT) enables the study of systems consisting of elements with similar atomic numbers. Processing datasets acquired using PCT is nontrivial because of the low-pass characteristics of the commonly used single-image phase retrieval algorithm. In this study, we introduce an image processing methodology that simultaneously utilizes both phase and attenuation components of an image obtained at a single detector distance. This novel method, combined with regularized Perona-Malik filter and bias-corrected fuzzy C-means algorithm, allows for automated segmentation of data acquired through four-dimensional PCT. Using this integrated approach, the three-dimensional coarsening morphology of an Aluminum-29.9wt% Silicon alloy can be analyzed.

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X-ray computed tomography of wood-adhesive bondlines: attenuation and phase-contrast effects

2015

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Microscale X-ray computed tomography (XCT) is discussed as a technique for identifying 3D adhesive distribution in wood-adhesive bondlines. Visualization and material segmentation of the adhesives from the surrounding cellular structures require sufficient gray-scale contrast in the reconstructed XCT data. Commercial wood-adhesive polymers have similar chemical characteristics and density to wood cell wall polymers and therefore do not provide good XCT attenuation contrast in their native form. Here, three different adhesive types, namely phenol formaldehyde, polymeric diphenylmethane diisocyanate, and a hybrid polyvinyl acetate, are tagged with iodine such that they yield sufficient X-ray attenuation contrast. However, phase-contrast effects at material edges complicate image quality and segmentation in XCT data reconstructed with conventional filtered backprojection absorption contrast algorithms. A quantitative phase retrieval algorithm, which isolates and removes the phase-contrast effect, was demonstrated. The article discusses and illustrates the balance between material X-ray attenuation and phase-contrast effects in all quantitative XCT analyses of wood-adhesive bondlines.

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Phase-contrast X-ray tomography: Contrast mechanism and roles of phase retrieval

Cited by 34 publications

References 12 publications

Evaluation of the Dual-Modal usage of contrast agents by means of Synchrotron X-ray Computed Microtomography and Magnetic Resonance Imaging using Macrophages loaded with Barium Sulfate and Gadolinium Nanoparticles for Detection and Monitoring in Animal Disease Models

Evaluation of the Dual-Modal usage of contrast agents by means of Synchrotron X-ray Computed Microtomography and Magnetic Resonance Imaging using Macrophages loaded with Barium Sulfate and Gadolinium Nanoparticles for Detection and Monitoring in Animal Disease Models

Integrated approach to the data processing of four-dimensional datasets from phase-contrast x-ray tomography

X-ray computed tomography of wood-adhesive bondlines: attenuation and phase-contrast effects

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