Emmanuel Brun - Academia.edu (original) (raw)

Papers by Emmanuel Brun

Proceedings of the National Academy of Sciences, 2012

Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ... more Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ∼10-20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 μm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ∼74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses. radiation dose reduction | iterative algorithm | analyzer based imaging M ammography is a widely used imaging technique for early detection of human breast cancers. Although more advanced technologies such as digital mammography have been developed to improve its image quality (1), there are three potential risks associated with mammography. First, mammograms miss up to 20% of breast cancers that are present during the time of screening (2). Second, in some cases mammograms appear abnormal, but no breast cancers are actually present (3). Third, repeated mammography examinations have the potential of causing cancers (4). Dedicated breast computed tomography (CT) can reduce some of these risks, but its spatial resolution (∼400 μm) is mainly limited by the X-ray dose deliverable to the radiationsensitive human breast and its detection of microcalcifications is inferior to mammography (5). Furthermore, some tumors are not visible in CT because its image contrast is based on the X-ray absorption coefficient and is intrinsically low between tumors and normal tissues. A very promising approach to significantly improve the image resolution, image contrast and detectability is the use of phase contrast x-ray tomography (PCT) (6-8) (Materials and Methods). Compared with absorption-based CT, PCT is sensitive to the refraction (i.e., "phase shift") of X-rays in matter. In soft tissues, phase variations can be two to three orders of magnitude larger than the absorption ones (9), and thus an increased image contrast can be achieved. Over the past few decades, phase contrast X-ray imaging has been under rapid development and various X-ray phase contrast methods have been implemented, including X-ray interferometry (6, 7), analyzer-based (or diffraction-enhanced) imaging (10, 11), propagation-based imaging (12, 13), grating-based imaging (14, 15), and grating noninterferometric methods (16). A large number of X-ray phase contrast imaging results has been reported on both technical developments and biomedical applications (6-20). In vitro and in vivo biomedical studies have focused on demonstrating high diagnostic significance of PCI images in a wide range of pathologies related to breast (8), joint and cartilage , lung (18), and central nervous system . Clinical trials have also been performed in PCI mammography (20). Furthermore, the development of advanced optics for the use of 50-80 keV (instead of 15-30 keV) X-rays has dramatically increased the sample size under study in PCT (8,. However, presently two of the major challenges prevent PCT from becoming an in vivo imaging tool for clinical application. First, to achieve high resolutions (i.e., tens of microns) for accurate diagnosis, PCT requires several thousands of projections from a whole human breast. The total radiation dose delivered to the breast is thus higher than that in dual-view mammography. Second, PCT uses sophisticated X-ray optics and the acquisition time for several thousands of projections is usually too long for clinical application.

Physics in medicine and biology, Jan 9, 2015

X-ray refraction-based computer tomography imaging is a well-established method for nondestructiv... more X-ray refraction-based computer tomography imaging is a well-established method for nondestructive investigations of various objects. In order to perform the 3D reconstruction of the index of refraction, two or more raw computed tomography phase-contrast images are usually acquired and combined to retrieve the refraction map (i.e. differential phase) signal within the sample. We suggest an approximate method to extract the refraction signal, which uses a single raw phase-contrast image. This method, here applied to analyzer-based phase-contrast imaging, is employed to retrieve the index of refraction map of a biological sample. The achieved accuracy in distinguishing the different tissues is comparable with the non-approximated approach. The suggested procedure can be used for precise refraction computer tomography with the advantage of a reduction of at least a factor of two of both the acquisition time and the dose delivered to the sample with respect to any of the other algorithm...

Optics Express, 2014

The refractive-index gradient vector field approach establishes a connection between a tomographi... more The refractive-index gradient vector field approach establishes a connection between a tomographic data set of differential phase contrast images and the distribution of the partial spatial derivatives of the refractive index in an object. The reconstruction of the refractive index in a plane requires the integration of its gradient field. This work shows how this integration can be efficiently performed by converting the problem to the Poisson equation, which can be accurately solved even in the case of noisy and large datasets. The performance of the suggested method is discussed and demonstrated experimentally by computing the refractive index distribution in both a simple plastic phantom and a complex biological sample. The quality of the reconstruction is evaluated through the direct comparison with other commonly used methods. To this end, the refractive index is retrieved from the same data set using also (1) the filtered backprojection algorithm for gradient projections, and (2) the regularized phase-retrieval procedure. Results show that the gradient vector field approach combined with the developed integration technique provides a very accurate depiction of the sample internal structure. Contrary to the two other techniques, the considered method does not require a preliminary phase-retrieval and can be implemented with any advanced computer tomography algorithm. In this work, analyzer-based phase contrast images are used for demonstration. Results, however, are generally valid and can be applied for processing differential phase-contrast tomographic data sets obtained with other phase-contrast imaging techniques.

Biomedical Optics Express, 2013

One of the most promising applications of the X-ray phasecontrast imaging is the three dimensiona... more One of the most promising applications of the X-ray phasecontrast imaging is the three dimensional tomographic reconstruction of the index of refraction. However, results reported so far are limited to relatively small samples. We present here the tomographic reconstruction of the index of refraction distribution of a large biomedical sample (> 10 cm diameter). A quantitative study comparing the absorption and phase contrast (analyzer-based) tomography images shows that the distribution of the index of refraction obtained with the phase contrast method provides a more accurate depiction (3-10 times larger signal to noise ratio values) of the sample internal structure. Thanks to the higher sensitivity of this method, the improved precision was obtained using an incoming photon fluence on the sample several times smaller than in the case of absorption imaging.

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Investigative Radiology, 2014

Objectives: This study evaluates high-resolution tomographic x-ray phasecontrast imaging in whole... more Objectives: This study evaluates high-resolution tomographic x-ray phasecontrast imaging in whole human knee joints for the depiction of soft tissue with emphasis on hyaline cartilage. The method is compared with conventional computed tomography (CT), synchrotron radiation absorption-based CT, and magnetic resonance imaging (MRI). Material and Methods: After approval of the institutional review board, 2 cadaveric human knees were examined at an synchrotron institution using a monochromatic x-ray beam of 60 keV, a detector with a 90-mm 2 field of view, and a pixel size of 46 Â 46 Km 2 . Images of phase-contrast imaging CT were reconstructed with the filtered back projection algorithm and the equally sloped tomography method. Image quality and tissue contrast were evaluated and compared in all modalities and with histology. Results: Phase-contrast imaging provides visualization of altered cartilage regions invisible in absorption CT with simultaneous high detail of the underlying bony abnormalities. The delineation of surface changes is similar to 3-T MRI using cartilage-dedicated sequences. Phase-contrast imaging CT presents soft tissue contrast surpassing that of conventional CT with a clear discrimination of ligamentous, muscular, neural, and vascular structures. In addition, phase-contrast imaging images show cartilage and meniscal calcifications that are not perceptible on conventional CT or on MRI. Conclusions: Phase-contrast imaging CT may facilitate a more complete evaluation of the human knee joint by providing concurrent comprehensive information about cartilage, the underlying subchondral bone, and their changes in osteoarthritic conditions. with the ability to detect actual cartilage changes. In the near future, these remarkable characteristics of PCI might be very useful for studies using animal models for the assessment of osteoarthritic evolution or therapy effect monitoring.

Applied Physics Letters, 2012

ABSTRACT Micro-beam x-ray absorption fine structure spectroscopy was used to investigate rutile T... more ABSTRACT Micro-beam x-ray absorption fine structure spectroscopy was used to investigate rutile TiO2 nanoparticles internalized into gastrointestinal cells during their crossing of a gut model barrier. Nanoparticles diluted in culture medium tend to accumulate in cells after 48 h exposure; however, no spectral differences arise between particles in cellular and in acellular environments, as corroborated by quantitative analysis. This finding establishes that no modification of the lattice properties of the nanoparticles occurs upon interaction with the barrier. These measurements demonstrate the possibility of interrogating nanoparticles in situ within cells, suggesting a way to investigate their fate when incorporated in biological hosts.

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Defect and Diffusion Forum, 2010

This paper presents an experimental and numerical study of heat and mass transfer in a porous cha... more This paper presents an experimental and numerical study of heat and mass transfer in a porous channel crossed by a gravity driven or forced fluid flow. We measured mass flux and local and overall heat transfer coefficients. In the gravity driven case, a maximal mass flux is observed, for which a maximal heat flux is measured. We propose an analytical model based on the Forchheimer law to determine this mass flux. Pore scale numerical simulations were used to provide local quantities and provide complementary interpretation of experimental data. Finally, we have shown that only a part of the foam is efficient for heat transfer and we have determined a foam active length. We propose an analytical model to evaluate this active length. A u t h o r P r o o f Younis, L. B., Cross-flow heat exchanger embedded within a porous medium, A u t h o r P r o o f

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomograp... more We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomography. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per experiment) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data volume or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estimating, in the absence of ground-truth data, the optimal parameters values for a priori techniques.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomograp... more We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomography. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per experiment) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data volume or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estimating, in the absence of ground-truth data, the optimal parameters values for a priori techniques.

Optics Letters, 2011

A nontomography approach for the measurement of angular-dependent coherent-scatter cross section ... more A nontomography approach for the measurement of angular-dependent coherent-scatter cross section of x rays (E≃40-80 keV) is described. It is shown that an analyzer crystal, which is proposed to be used for the sampling of the cross section, simultaneously provides information about the location of the scattering volume inside the object. A numerical simulation demonstrates that this method can be applied for nondestructive analysis of an object's internal structure.

Chemical Engineering Science, 2012

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Proceedings of the National Academy of Sciences, 2012

Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ... more Mammography is the primary imaging tool for screening and diagnosis of human breast cancers, but ∼10-20% of palpable tumors are not detectable on mammograms and only about 40% of biopsied lesions are malignant. Here we report a high-resolution, low-dose phase contrast X-ray tomographic method for 3D diagnosis of human breast cancers. By combining phase contrast X-ray imaging with an image reconstruction method known as equally sloped tomography, we imaged a human breast in three dimensions and identified a malignant cancer with a pixel size of 92 μm and a radiation dose less than that of dual-view mammography. According to a blind evaluation by five independent radiologists, our method can reduce the radiation dose and acquisition time by ∼74% relative to conventional phase contrast X-ray tomography, while maintaining high image resolution and image contrast. These results demonstrate that high-resolution 3D diagnostic imaging of human breast cancers can, in principle, be performed at clinical compatible doses. radiation dose reduction | iterative algorithm | analyzer based imaging M ammography is a widely used imaging technique for early detection of human breast cancers. Although more advanced technologies such as digital mammography have been developed to improve its image quality (1), there are three potential risks associated with mammography. First, mammograms miss up to 20% of breast cancers that are present during the time of screening (2). Second, in some cases mammograms appear abnormal, but no breast cancers are actually present (3). Third, repeated mammography examinations have the potential of causing cancers (4). Dedicated breast computed tomography (CT) can reduce some of these risks, but its spatial resolution (∼400 μm) is mainly limited by the X-ray dose deliverable to the radiationsensitive human breast and its detection of microcalcifications is inferior to mammography (5). Furthermore, some tumors are not visible in CT because its image contrast is based on the X-ray absorption coefficient and is intrinsically low between tumors and normal tissues. A very promising approach to significantly improve the image resolution, image contrast and detectability is the use of phase contrast x-ray tomography (PCT) (6-8) (Materials and Methods). Compared with absorption-based CT, PCT is sensitive to the refraction (i.e., "phase shift") of X-rays in matter. In soft tissues, phase variations can be two to three orders of magnitude larger than the absorption ones (9), and thus an increased image contrast can be achieved. Over the past few decades, phase contrast X-ray imaging has been under rapid development and various X-ray phase contrast methods have been implemented, including X-ray interferometry (6, 7), analyzer-based (or diffraction-enhanced) imaging (10, 11), propagation-based imaging (12, 13), grating-based imaging (14, 15), and grating noninterferometric methods (16). A large number of X-ray phase contrast imaging results has been reported on both technical developments and biomedical applications (6-20). In vitro and in vivo biomedical studies have focused on demonstrating high diagnostic significance of PCI images in a wide range of pathologies related to breast (8), joint and cartilage , lung (18), and central nervous system . Clinical trials have also been performed in PCI mammography (20). Furthermore, the development of advanced optics for the use of 50-80 keV (instead of 15-30 keV) X-rays has dramatically increased the sample size under study in PCT (8,. However, presently two of the major challenges prevent PCT from becoming an in vivo imaging tool for clinical application. First, to achieve high resolutions (i.e., tens of microns) for accurate diagnosis, PCT requires several thousands of projections from a whole human breast. The total radiation dose delivered to the breast is thus higher than that in dual-view mammography. Second, PCT uses sophisticated X-ray optics and the acquisition time for several thousands of projections is usually too long for clinical application.

Physics in medicine and biology, Jan 9, 2015

X-ray refraction-based computer tomography imaging is a well-established method for nondestructiv... more X-ray refraction-based computer tomography imaging is a well-established method for nondestructive investigations of various objects. In order to perform the 3D reconstruction of the index of refraction, two or more raw computed tomography phase-contrast images are usually acquired and combined to retrieve the refraction map (i.e. differential phase) signal within the sample. We suggest an approximate method to extract the refraction signal, which uses a single raw phase-contrast image. This method, here applied to analyzer-based phase-contrast imaging, is employed to retrieve the index of refraction map of a biological sample. The achieved accuracy in distinguishing the different tissues is comparable with the non-approximated approach. The suggested procedure can be used for precise refraction computer tomography with the advantage of a reduction of at least a factor of two of both the acquisition time and the dose delivered to the sample with respect to any of the other algorithm...

Optics Express, 2014

The refractive-index gradient vector field approach establishes a connection between a tomographi... more The refractive-index gradient vector field approach establishes a connection between a tomographic data set of differential phase contrast images and the distribution of the partial spatial derivatives of the refractive index in an object. The reconstruction of the refractive index in a plane requires the integration of its gradient field. This work shows how this integration can be efficiently performed by converting the problem to the Poisson equation, which can be accurately solved even in the case of noisy and large datasets. The performance of the suggested method is discussed and demonstrated experimentally by computing the refractive index distribution in both a simple plastic phantom and a complex biological sample. The quality of the reconstruction is evaluated through the direct comparison with other commonly used methods. To this end, the refractive index is retrieved from the same data set using also (1) the filtered backprojection algorithm for gradient projections, and (2) the regularized phase-retrieval procedure. Results show that the gradient vector field approach combined with the developed integration technique provides a very accurate depiction of the sample internal structure. Contrary to the two other techniques, the considered method does not require a preliminary phase-retrieval and can be implemented with any advanced computer tomography algorithm. In this work, analyzer-based phase contrast images are used for demonstration. Results, however, are generally valid and can be applied for processing differential phase-contrast tomographic data sets obtained with other phase-contrast imaging techniques.

Biomedical Optics Express, 2013

One of the most promising applications of the X-ray phasecontrast imaging is the three dimensiona... more One of the most promising applications of the X-ray phasecontrast imaging is the three dimensional tomographic reconstruction of the index of refraction. However, results reported so far are limited to relatively small samples. We present here the tomographic reconstruction of the index of refraction distribution of a large biomedical sample (> 10 cm diameter). A quantitative study comparing the absorption and phase contrast (analyzer-based) tomography images shows that the distribution of the index of refraction obtained with the phase contrast method provides a more accurate depiction (3-10 times larger signal to noise ratio values) of the sample internal structure. Thanks to the higher sensitivity of this method, the improved precision was obtained using an incoming photon fluence on the sample several times smaller than in the case of absorption imaging.

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Investigative Radiology, 2014

Objectives: This study evaluates high-resolution tomographic x-ray phasecontrast imaging in whole... more Objectives: This study evaluates high-resolution tomographic x-ray phasecontrast imaging in whole human knee joints for the depiction of soft tissue with emphasis on hyaline cartilage. The method is compared with conventional computed tomography (CT), synchrotron radiation absorption-based CT, and magnetic resonance imaging (MRI). Material and Methods: After approval of the institutional review board, 2 cadaveric human knees were examined at an synchrotron institution using a monochromatic x-ray beam of 60 keV, a detector with a 90-mm 2 field of view, and a pixel size of 46 Â 46 Km 2 . Images of phase-contrast imaging CT were reconstructed with the filtered back projection algorithm and the equally sloped tomography method. Image quality and tissue contrast were evaluated and compared in all modalities and with histology. Results: Phase-contrast imaging provides visualization of altered cartilage regions invisible in absorption CT with simultaneous high detail of the underlying bony abnormalities. The delineation of surface changes is similar to 3-T MRI using cartilage-dedicated sequences. Phase-contrast imaging CT presents soft tissue contrast surpassing that of conventional CT with a clear discrimination of ligamentous, muscular, neural, and vascular structures. In addition, phase-contrast imaging images show cartilage and meniscal calcifications that are not perceptible on conventional CT or on MRI. Conclusions: Phase-contrast imaging CT may facilitate a more complete evaluation of the human knee joint by providing concurrent comprehensive information about cartilage, the underlying subchondral bone, and their changes in osteoarthritic conditions. with the ability to detect actual cartilage changes. In the near future, these remarkable characteristics of PCI might be very useful for studies using animal models for the assessment of osteoarthritic evolution or therapy effect monitoring.

Applied Physics Letters, 2012

ABSTRACT Micro-beam x-ray absorption fine structure spectroscopy was used to investigate rutile T... more ABSTRACT Micro-beam x-ray absorption fine structure spectroscopy was used to investigate rutile TiO2 nanoparticles internalized into gastrointestinal cells during their crossing of a gut model barrier. Nanoparticles diluted in culture medium tend to accumulate in cells after 48 h exposure; however, no spectral differences arise between particles in cellular and in acellular environments, as corroborated by quantitative analysis. This finding establishes that no modification of the lattice properties of the nanoparticles occurs upon interaction with the barrier. These measurements demonstrate the possibility of interrogating nanoparticles in situ within cells, suggesting a way to investigate their fate when incorporated in biological hosts.

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Defect and Diffusion Forum, 2010

This paper presents an experimental and numerical study of heat and mass transfer in a porous cha... more This paper presents an experimental and numerical study of heat and mass transfer in a porous channel crossed by a gravity driven or forced fluid flow. We measured mass flux and local and overall heat transfer coefficients. In the gravity driven case, a maximal mass flux is observed, for which a maximal heat flux is measured. We propose an analytical model based on the Forchheimer law to determine this mass flux. Pore scale numerical simulations were used to provide local quantities and provide complementary interpretation of experimental data. Finally, we have shown that only a part of the foam is efficient for heat transfer and we have determined a foam active length. We propose an analytical model to evaluate this active length. A u t h o r P r o o f Younis, L. B., Cross-flow heat exchanger embedded within a porous medium, A u t h o r P r o o f

Journal of Synchrotron Radiation, 2013

The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequen... more The Track Length Estimator method has been implemented in the GATE/Geant4 framework and subsequently validated experimentally and against the analogous Monte Carlo simulation. The tool allows performing dose simulations with a gain in time from 50 to 500 times compared to the standard Monte Carlo, without loss of accuracy.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomograp... more We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomography. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per experiment) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data volume or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estimating, in the absence of ground-truth data, the optimal parameters values for a priori techniques.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2014

We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomograp... more We present the PyHST2 code which is in service at ESRF for phase-contrast and absorption tomography. This code has been engineered to sustain the high data flow typical of the 3rd generation synchrotron facilities (10 terabytes per experiment) by adopting a distributed and pipelined architecture. The code implements, beside a default filtered backprojection reconstruction, iterative reconstruction techniques with a priori knowledge. These latter are used to improve the reconstruction quality or in order to reduce the required data volume or the deposited dose to the sample and reach a given quality goal. The implemented a priori knowledge techniques are based on the total variation penalization and a new recently found convex functional which is based on overlapping patches. We give details of the different methods and discuss how they are implemented in the PyHST2 code, which is distributed under free license. We provide methods for estimating, in the absence of ground-truth data, the optimal parameters values for a priori techniques.

Optics Letters, 2011

A nontomography approach for the measurement of angular-dependent coherent-scatter cross section ... more A nontomography approach for the measurement of angular-dependent coherent-scatter cross section of x rays (E≃40-80 keV) is described. It is shown that an analyzer crystal, which is proposed to be used for the sampling of the cross section, simultaneously provides information about the location of the scattering volume inside the object. A numerical simulation demonstrates that this method can be applied for nondestructive analysis of an object's internal structure.

Chemical Engineering Science, 2012

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