Vincent Revol - Academia.edu (original) (raw)

Papers by Vincent Revol

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Abstract—Ultra small angle scattering is a powerful tool for the study of the micro-structure of ... more Abstract—Ultra small angle scattering is a powerful tool for the study of the micro-structure of materials at a length scale below the resolution of standard x-ray detectors. Current methods like Small Angle X-ray Scattering (SAXS) are usually slow and there-fore inadequate to ...

Case Studies in Nondestructive Testing and Evaluation, 2015

X-ray differential phase contrast imaging (DPCI) with a Talbot-Lau interferometer setup allows th... more X-ray differential phase contrast imaging (DPCI) with a Talbot-Lau interferometer setup allows the simultaneous measurement of the spatial distribution of the real and imaginary part of the refractive index and of the locations of scattering centers of an object. Since the real part of the refractive index of X-rays is several orders of magnitude more important than the imaginary part phase contrast images of weakly absorbing samples show considerably better contrast than conventional attenuation contrast images (ACI). The possibility to obtain better image quality at lower radiation dose raised a lot of interest in the medical and science life communities. In contrast, the advantages of DPCI for material science are not yet well established. One reason are the difficulties encountered in producing the required phase and absorption grids for high energies (>50 keV). Other reasons are that the well-established ACI already delivers excellent results and that the radiation dose is a...

X-ray phase contrast imaging (XPCi) using the Talbot-Lau grating interferometer attracts increasi... more X-ray phase contrast imaging (XPCi) using the Talbot-Lau grating interferometer attracts increasing attention for its implementation in various fields of applications such as in the (bio-) medical domain, non-destructive testing or security. Since the method is compatible with laboratory X-ray tube sources as well as with large field of view digital X-ray image sensors, it has a large potential to provide XPCi for industrial and medical applications as widespread as conventional X-raying is. Here, we report on our recent results and measurements regarding the grating interferometer technology.

X-ray phase imaging including phase tomography has been attracting increasing attention during th... more X-ray phase imaging including phase tomography has been attracting increasing attention during the past few decades. The advantage of X-ray phase imaging is that an extremely high sensitivity is achieved for weakly absorbing materials, such as biological soft tissues, which generate a poor contrast by conventional schemes. Especially for such living samples, where the reduction of the applied dose is of paramount interest, phase sensitive measurements schemes have an inherent potential for a significant dose reduction combined with an image quality enhancement. Several methods have been invented for x-ray phase contrast imaging that either use an approach based on interferometry, diffraction or wave-field propagation. Some of these techniques have a potential for commercial applications, such as in medicine, nondestructive testing, security and inspection. The scope of this manuscript thus deals with one particular such technique that measures the diffraction caused by the specimen by means of a grating interferometer. Examples of measurements are shown that depict the potential of phase contrast imaging for future commercial applications, such as in medical imaging, non-destructive testing and inspection for quality control. The current state of the technology is briefly reviewed as well as its shortcomings to be overcome with regard to the applications.

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Abstract–The present work tackles the question on the evidence of X-ray phase contrast imaging wi... more Abstract–The present work tackles the question on the evidence of X-ray phase contrast imaging with regard to a potential application in medical diagnostics. For this study the Talbot-Lau interferometer method by means of X-ray diffraction gratings was used. Specimens of human organs ...

2011 IEEE Nuclear Science Symposium Conference Record, 2011

ABSTRACT In the presented work, we investigated the potential capabilities of contrast improvemen... more ABSTRACT In the presented work, we investigated the potential capabilities of contrast improvement in soft tissue achieved by x-ray phase contrast imaging. T he Talbot-Lau interferometer method was implemented by means of x-ray diffraction gratings. Tomographic measurements were performed on prepared samples containing specimens of different kinds of soft animal tissue. T he results showed that phase contrast can provide additional and complementary visualization of soft tissue structures that are invisible to conventional, attenuation contrast x-ray imaging. As an example, the results obtained from the tomography of a bovine artery show that whereas the fat and connective tissue present around the artery can be seen with both absorption and phase contrast, the artery itself can only be recognized in the phase contrast image. Moreover, the situation is even more complicated for specimens containing not only soft tissue but also stronger absorbers such as bones or cartilage. Indeed, the strongly absorbing bones also lead to the scattering of the x-ray beam (due to their dense micro-structure), which results in a loss of the phase information. However, this issue relaxes when higher x-ray energies are used. Measurements of specimens (containing bones and soft tissue) were demonstrated with the set-up optimized for a mean x-ray energy of 50keV.

Physics in Medicine and Biology, 2014

This paper introduces a new image denoising, fusion and enhancement framework for combining and o... more This paper introduces a new image denoising, fusion and enhancement framework for combining and optimal visualization of x-ray attenuation contrast (AC), differential phase contrast (DPC) and dark-field contrast (DFC) images retrieved from x-ray Talbot-Lau grating interferometry. The new image fusion framework comprises three steps: (i) denoising each input image (AC, DPC and DFC) through adaptive Wiener filtering, (ii) performing a two-step image fusion process based on the shift-invariant wavelet transform, i.e. first fusing the AC with the DPC image and then fusing the resulting image with the DFC image, and finally (iii) enhancing the fused image to obtain a final image using adaptive histogram equalization, adaptive sharpening and contrast optimization. Application examples are presented for two biological objects (a human tooth and a cherry) and the proposed method is compared to two recently published AC/DPC/DFC image processing techniques. In conclusion, the new framework for the processing of AC, DPC and DFC allows the most relevant features of all three images to be combined in one image while reducing the noise and enhancing adaptively the relevant image features. The newly developed framework may be used in technical and medical applications.

Optics Express, 2011

X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer s... more X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer setup allows visualizing the threedimensional distribution of the refractive index by measuring the shifts of an interference pattern due to phase variations of the X-ray beam. Unfortunately, severe reconstruction artifacts appear in the presence of differential phase wrapping and clipping. In this paper, we propose to use the attenuation contrast, which is obtained from the same measurement, for correcting the DPC signal. Using the example of a DPC CT measurement with pronounced phase artifacts, we will discuss the efficiency of our phase artifact correction method.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

Recently, a Talbot–Lau interferometer was proposed to achieve phase contrast and dark field imagi... more Recently, a Talbot–Lau interferometer was proposed to achieve phase contrast and dark field imaging in the hard X-rays domain (10–100keV). This technique attracts much interest since it does not impose strong requirements on the coherence of the radiation while ...

Journal of Applied Physics, 2012

ABSTRACT X-ray scatter dark field imaging with a grating interferometer is becoming a standard to... more ABSTRACT X-ray scatter dark field imaging with a grating interferometer is becoming a standard tool for the characterization of microscopic texture of samples. Recently, it was shown that directional information could also be recovered when the sample displays an anisotropic ordering such as, for instance, a bundle of microscopic fibers. Here, we demonstrate that previously suggested approaches are ambiguous when multiple anisotropic orientations coexist in the sample. Therefore, we developed a new orientation-selective approach which allows for separating the contributions of individual orientations provided that these orientations are known a-priori. The method, demonstrated experimentally using a well-defined wood sample, is envisioned to be of high interest for the non-destructive inspection of composite materials. © 2012 American Institute of Physics.

NDT & E International, 2013

a b s t r a c t X-ray scatter dark field imaging (SDFI) using a Talbot-Lau grating interferometer... more a b s t r a c t X-ray scatter dark field imaging (SDFI) using a Talbot-Lau grating interferometer has recently attracted growing interest for the non-destructive testing and evaluation of light materials. In this work, we developed the method further for the characterisation of the laminate structure of carbon fibre reinforced polymers. In particular, we used the anisotropic properties of the small angle scattering signal to image the fibre bundles running in different directions independently with excellent contrast. The results obtained for four different woven carbon fibre reinforced polymer samples were compared to high resolution X-ray computed tomography results. We found that SDFI allows for the visualisation of the weave pattern structure and analysis of the size of the carbon fibre bundle in three dimensions, even if the individual fibres cannot be separated or the absorption contrast between the carbon fibres and the epoxy matrix is very low.

ABSTRACT This paper reports on the latest developments in the manufacturing of high aspect ratio ... more ABSTRACT This paper reports on the latest developments in the manufacturing of high aspect ratio silicon-based gratings used for X-ray phase contrast imaging (XPCI). Grating-based XPCI provides, in one measurement, unique information about the absorption coefficient, the index of refraction and the microscopic structure of a sample at hard X-ray frequencies. For this reason, XPCI can potentially overcome the limitations of classical absorption-based radiography, notably for weakly absorbing materials. New micro-fabrication processes were developed to manufacture full set of large area and high aspect ratio X-ray gratings with few defects. The complementarity of XPCI with conventional absorption-based radiography was experimentally demonstrated.

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Abstract—Ultra small angle scattering is a powerful tool for the study of the micro-structure of ... more Abstract—Ultra small angle scattering is a powerful tool for the study of the micro-structure of materials at a length scale below the resolution of standard x-ray detectors. Current methods like Small Angle X-ray Scattering (SAXS) are usually slow and there-fore inadequate to ...

Case Studies in Nondestructive Testing and Evaluation, 2015

X-ray differential phase contrast imaging (DPCI) with a Talbot-Lau interferometer setup allows th... more X-ray differential phase contrast imaging (DPCI) with a Talbot-Lau interferometer setup allows the simultaneous measurement of the spatial distribution of the real and imaginary part of the refractive index and of the locations of scattering centers of an object. Since the real part of the refractive index of X-rays is several orders of magnitude more important than the imaginary part phase contrast images of weakly absorbing samples show considerably better contrast than conventional attenuation contrast images (ACI). The possibility to obtain better image quality at lower radiation dose raised a lot of interest in the medical and science life communities. In contrast, the advantages of DPCI for material science are not yet well established. One reason are the difficulties encountered in producing the required phase and absorption grids for high energies (>50 keV). Other reasons are that the well-established ACI already delivers excellent results and that the radiation dose is a...

X-ray phase contrast imaging (XPCi) using the Talbot-Lau grating interferometer attracts increasi... more X-ray phase contrast imaging (XPCi) using the Talbot-Lau grating interferometer attracts increasing attention for its implementation in various fields of applications such as in the (bio-) medical domain, non-destructive testing or security. Since the method is compatible with laboratory X-ray tube sources as well as with large field of view digital X-ray image sensors, it has a large potential to provide XPCi for industrial and medical applications as widespread as conventional X-raying is. Here, we report on our recent results and measurements regarding the grating interferometer technology.

X-ray phase imaging including phase tomography has been attracting increasing attention during th... more X-ray phase imaging including phase tomography has been attracting increasing attention during the past few decades. The advantage of X-ray phase imaging is that an extremely high sensitivity is achieved for weakly absorbing materials, such as biological soft tissues, which generate a poor contrast by conventional schemes. Especially for such living samples, where the reduction of the applied dose is of paramount interest, phase sensitive measurements schemes have an inherent potential for a significant dose reduction combined with an image quality enhancement. Several methods have been invented for x-ray phase contrast imaging that either use an approach based on interferometry, diffraction or wave-field propagation. Some of these techniques have a potential for commercial applications, such as in medicine, nondestructive testing, security and inspection. The scope of this manuscript thus deals with one particular such technique that measures the diffraction caused by the specimen by means of a grating interferometer. Examples of measurements are shown that depict the potential of phase contrast imaging for future commercial applications, such as in medical imaging, non-destructive testing and inspection for quality control. The current state of the technology is briefly reviewed as well as its shortcomings to be overcome with regard to the applications.

IEEE Nuclear Science Symposuim & Medical Imaging Conference, 2010

Abstract–The present work tackles the question on the evidence of X-ray phase contrast imaging wi... more Abstract–The present work tackles the question on the evidence of X-ray phase contrast imaging with regard to a potential application in medical diagnostics. For this study the Talbot-Lau interferometer method by means of X-ray diffraction gratings was used. Specimens of human organs ...

2011 IEEE Nuclear Science Symposium Conference Record, 2011

ABSTRACT In the presented work, we investigated the potential capabilities of contrast improvemen... more ABSTRACT In the presented work, we investigated the potential capabilities of contrast improvement in soft tissue achieved by x-ray phase contrast imaging. T he Talbot-Lau interferometer method was implemented by means of x-ray diffraction gratings. Tomographic measurements were performed on prepared samples containing specimens of different kinds of soft animal tissue. T he results showed that phase contrast can provide additional and complementary visualization of soft tissue structures that are invisible to conventional, attenuation contrast x-ray imaging. As an example, the results obtained from the tomography of a bovine artery show that whereas the fat and connective tissue present around the artery can be seen with both absorption and phase contrast, the artery itself can only be recognized in the phase contrast image. Moreover, the situation is even more complicated for specimens containing not only soft tissue but also stronger absorbers such as bones or cartilage. Indeed, the strongly absorbing bones also lead to the scattering of the x-ray beam (due to their dense micro-structure), which results in a loss of the phase information. However, this issue relaxes when higher x-ray energies are used. Measurements of specimens (containing bones and soft tissue) were demonstrated with the set-up optimized for a mean x-ray energy of 50keV.

Physics in Medicine and Biology, 2014

This paper introduces a new image denoising, fusion and enhancement framework for combining and o... more This paper introduces a new image denoising, fusion and enhancement framework for combining and optimal visualization of x-ray attenuation contrast (AC), differential phase contrast (DPC) and dark-field contrast (DFC) images retrieved from x-ray Talbot-Lau grating interferometry. The new image fusion framework comprises three steps: (i) denoising each input image (AC, DPC and DFC) through adaptive Wiener filtering, (ii) performing a two-step image fusion process based on the shift-invariant wavelet transform, i.e. first fusing the AC with the DPC image and then fusing the resulting image with the DFC image, and finally (iii) enhancing the fused image to obtain a final image using adaptive histogram equalization, adaptive sharpening and contrast optimization. Application examples are presented for two biological objects (a human tooth and a cherry) and the proposed method is compared to two recently published AC/DPC/DFC image processing techniques. In conclusion, the new framework for the processing of AC, DPC and DFC allows the most relevant features of all three images to be combined in one image while reducing the noise and enhancing adaptively the relevant image features. The newly developed framework may be used in technical and medical applications.

Optics Express, 2011

X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer s... more X-ray differential phase contrast computed tomography (DPC CT) with a Talbot-Lau interferometer setup allows visualizing the threedimensional distribution of the refractive index by measuring the shifts of an interference pattern due to phase variations of the X-ray beam. Unfortunately, severe reconstruction artifacts appear in the presence of differential phase wrapping and clipping. In this paper, we propose to use the attenuation contrast, which is obtained from the same measurement, for correcting the DPC signal. Using the example of a DPC CT measurement with pronounced phase artifacts, we will discuss the efficiency of our phase artifact correction method.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

Recently, a Talbot–Lau interferometer was proposed to achieve phase contrast and dark field imagi... more Recently, a Talbot–Lau interferometer was proposed to achieve phase contrast and dark field imaging in the hard X-rays domain (10–100keV). This technique attracts much interest since it does not impose strong requirements on the coherence of the radiation while ...

Journal of Applied Physics, 2012

ABSTRACT X-ray scatter dark field imaging with a grating interferometer is becoming a standard to... more ABSTRACT X-ray scatter dark field imaging with a grating interferometer is becoming a standard tool for the characterization of microscopic texture of samples. Recently, it was shown that directional information could also be recovered when the sample displays an anisotropic ordering such as, for instance, a bundle of microscopic fibers. Here, we demonstrate that previously suggested approaches are ambiguous when multiple anisotropic orientations coexist in the sample. Therefore, we developed a new orientation-selective approach which allows for separating the contributions of individual orientations provided that these orientations are known a-priori. The method, demonstrated experimentally using a well-defined wood sample, is envisioned to be of high interest for the non-destructive inspection of composite materials. © 2012 American Institute of Physics.

NDT & E International, 2013

a b s t r a c t X-ray scatter dark field imaging (SDFI) using a Talbot-Lau grating interferometer... more a b s t r a c t X-ray scatter dark field imaging (SDFI) using a Talbot-Lau grating interferometer has recently attracted growing interest for the non-destructive testing and evaluation of light materials. In this work, we developed the method further for the characterisation of the laminate structure of carbon fibre reinforced polymers. In particular, we used the anisotropic properties of the small angle scattering signal to image the fibre bundles running in different directions independently with excellent contrast. The results obtained for four different woven carbon fibre reinforced polymer samples were compared to high resolution X-ray computed tomography results. We found that SDFI allows for the visualisation of the weave pattern structure and analysis of the size of the carbon fibre bundle in three dimensions, even if the individual fibres cannot be separated or the absorption contrast between the carbon fibres and the epoxy matrix is very low.

ABSTRACT This paper reports on the latest developments in the manufacturing of high aspect ratio ... more ABSTRACT This paper reports on the latest developments in the manufacturing of high aspect ratio silicon-based gratings used for X-ray phase contrast imaging (XPCI). Grating-based XPCI provides, in one measurement, unique information about the absorption coefficient, the index of refraction and the microscopic structure of a sample at hard X-ray frequencies. For this reason, XPCI can potentially overcome the limitations of classical absorption-based radiography, notably for weakly absorbing materials. New micro-fabrication processes were developed to manufacture full set of large area and high aspect ratio X-ray gratings with few defects. The complementarity of XPCI with conventional absorption-based radiography was experimentally demonstrated.