J. Tabary - Academia.edu (original) (raw)

Papers by J. Tabary

The application of a radiographic inspection procedure in nuclear NDE requires a formal demonstra... more The application of a radiographic inspection procedure in nuclear NDE requires a formal demonstration of the procedure's capability to detect the supposed defects. The French RSE-M code authorizes different means to achieve the performance demonstration, such as experience feedback , experiments on mock-ups and computer modeling, which are often employed in combination. To enable performance demonstration, a new gamma and X-Ray simulation module has been integrated to the CIVA software platform and completes the already available UT and ET modules. This module is based on a combination of NDT radiographic simulation modules developed at the CEA LETI and at EDF R&D. Direct radiation is calculated from an analytical approach (ray tracer and Beer-Lambert law for the attenuation) while the scattered radiation is simulated by Monte-Carlo modeling. In this context CIVA X-Ray enables simulating a realistic and complex inspection configuration taking into account the most influential parameters of a radiographic inspection. In this paper we illustrate how CIVA-RX addresses the specific requirements of nuclear NDE on radiographic modeling, present examples from three typical application domains, and elaborate on the assessment of an indication's visibility. SPECIFIC REQUIREMENTS ON COMPUTER MODELING OF RADIOGRAPHIC INSPECTIONS OF NUCLEAR COMPONENTS Radiographic inspection as a non destructive inspection technique is commonly used in numerous application domains, such as aerospace, chemistry, oil/off shore, archeology and nuclear power plants, each of which has specific requirements which must be addressed individually. As opposed to aerospace applications, the components inspected in nuclear applications have two specific properties: More info about this article: http://www.ndt.net/?id=8821 More info about this article:

Nondestructive Testing of Materials and Structures, 2011

Computer modelling of non-destructive testing methods has come a long way from the beginnings in ... more Computer modelling of non-destructive testing methods has come a long way from the beginnings in the mid 90s to today. Radiographic modelling for components with higher wall thicknesses, as they are typical for nuclear applications, must include precise predictions of scattered radiation and its impact in terms of contrast reduction. Dedicated or general purpose Monte Carlo methods with the ability to calculate higher order scattering events are the state of the art for these applications. Aerospace applications, on the other hand, have stronger requirements on the modelling code’s capabilities to import complex CAD geometries, and can benefit from faster analytical scatter models, limited to first or second order scattering events. Similar distinctions can be made for the various approaches proposed to accurately model geometrical and film unsharpness, film granularity, film responses, film/foil cartridges and photon noise. This article presents a state-of-the-art review of radiographic modelling from the perspective of two important application domains with very different requirements, nuclear and aerospace.

AIP Conference Proceedings, 2010

ABSTRACT Code Validation is a permanent concern in computer simulation, and has been addressed re... more ABSTRACT Code Validation is a permanent concern in computer simulation, and has been addressed repeatedly in eddy current and ultrasonic modelling. A good benchmark problem is sufficiently simple to be taken into account by various codes without strong requirements on geometry representation capabilities, focuses on few or even a single aspect of the problem at hand to facilitate interpretation and to avoid that compound errors compensate themselves, yields a quantitative result and is experimentally accessible. In this paper we attempt to address code validation for one aspect of radio-graphic modelling, the scattered radiation prediction. An update of the results of the 2008 benchmark is presented. Additionally we discuss the extension of this benchmark on the lower energy part for 60 and 80 keV as well as for higher energies up to 10 MeV to study the contribution of pair production. Of special interest will be the primary radiation (attenuation law as reference), the total scattered radiation, the relative contribution of scattered radiation separated by order of scatter events (1st, 2nd, ..., 20th), and the spectrum of scattered radiation. We present the results of three Monte Carlo codes (MC-Ray, Sindbad and Moderato) as well as an analytical first order scattering code (VXI) and compare to MCNP as reference. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

A new gamma and X-Ray simulation module has been integrated to the CIVA software and completes th... more A new gamma and X-Ray simulation module has been integrated to the CIVA software and completes the already available UT and ECT modules. This module is based on a combination of NDT radiographic modules developed at the CEA LETI and at EDF R&D. Direct radiation is calculated from an analytical appro ach (ray tracer and Beer-Lambert law for the attenuation) while the scattered radiation is s imulated by Monte-Carlo modelling. Different types of sources, gamma or X-rays, and differ ent detectors can be simulated. The X ray module uses the same dedicated Graphical User Interfa ce mutual to UT and ECT techniques. It helps to simulate control of specimens whe re the geometry can be imported from a CAD tool and also to put in evidence the presence of defects (with canonical geometries or also defined from a CAD tool). In this article, after a description of the different models used, the X-Ray simulation possibilities are illustrated on different practical ap plications.

2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014

New horizons in x-ray radiography and computed tomography (CT) have been opened up with the emerg... more New horizons in x-ray radiography and computed tomography (CT) have been opened up with the emergence of energy resolved x-ray imaging. This includes the ability to differentiate material components and estimate their equivalent thickness or relative ratio by processing a single shot acquisition image. However, such techniques require highly accurate images, especially for materials close in terms of attenuation. The presence of scattered radiation leads to a loss of contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to evaluate the disturbance caused by scatter on multi-energy imaging, more precisely, on a material decomposition approach commonly used in radiography or CT. This evaluation was based on numerical simulations using Sindbad-SFFD. Results showed a significant impact of scattered radiation on quantification accuracy for a simplified thorax-sized numerical phantom with an average error of 157.1% and 74.1% for cortical bone and water thickness, respectively. When only 10% of scatter was considered the error still remained significant: 35.1% and 17.5% for cortical bone and water thickness, respectively. The study concludes that a scatter correction method should be performed prior to any material decomposition, if one aims to benefit from energy resolved data in an uncollimated geometry.

2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)

A fully three-dimensional model of a semiconductor gamma-ray detector is presented. The model tak... more A fully three-dimensional model of a semiconductor gamma-ray detector is presented. The model takes into account the gamma-ray and charge collection physical phenomena involved in the detection process and models the readout electronic response and noise. The model successively involves the Monte Carlo simulation of the photon transport, the finite element transient computation of the adjoint transport equation, and the

Backscatter X-ray technique is particularly convenient for the inspection of single-sided access ... more Backscatter X-ray technique is particularly convenient for the inspection of single-sided access objects, in order to detect subsurface defects or control subsurface layers thickness. This well known technique can benefit today from recent developments in detectors technology. Backscatter technique requires many parameters: relative geometry of source, detector and object, and associated collimation. In order to help the design of backscatter systems, we have developed a software simulation tool, able to predict the backscatter signals for given systems and objects. Theoretically, such a simulation should be performed based on Monte Carlo code to manage multiple scatter interactions. We propose a version based on analytical computation, allowing fast simulation, and a modified one using partially a Monte Carlo code, if more accuracy is required. Experimental measurements are compared to simulation. The proposed tool can also help the interpretation and analysis of backscatter signal...

SPIE Proceedings, 2003

ABSTRACT Osteoporosis is a disease characterized by a decrease of bone mineral density as well as... more ABSTRACT Osteoporosis is a disease characterized by a decrease of bone mineral density as well as by architecture modification leading to an increase of fracture risk. This paper is part of study investigating the possibility to extract some structural parameters quantifying trabecular bone architecture from radiographies realized in vivo. The first step of the study is the definition of optimum radiographic conditions (X-ray spectrum, detector) as well as the development of adapted image processing tools to extract relevant indexes characterizing architecture. Therefore a simulation process computing synthetic radiographies from trabecular bone samples has been developed. This process is done in three distinct steps: (1) Computation of a very high spatial resolution 3D muCT volume of a human trabecular bone sample from a series of acquisitions with a microtomography system using synchrotron radiation. (2) Transformation of the muCT volume in a materials voxel volume. (3) Simulation of the radiography projection by using the X-ray radiographic simulation software Sindbad. The simulation software provides a lot of parameters which can be easily modified (spectra, materials, geometry, detector...) so that its use for an optimisation purpose is very practical. Comparison of simulated and experimental radiographies performed under synchrotron radiation microtomography configuration validates the accuracy of our simulation process. Simulated radiographs under several clinical conditions are also presented.

Proceedings - 2012 IEEE 2nd Conference on Healthcare Informatics, Imaging and Systems Biology, HISB 2012, 2012

This paper describes the creation of a comprehensive conceptualization of object models used in m... more This paper describes the creation of a comprehensive conceptualization of object models used in medical image simulation, suitable for major imaging modalities and simulators. The goal is to create an application ontology that can be used to annotate the models in a repository integrated in the Virtual Imaging Platform (VIP), to facilitate their sharing and reuse. Annotations make the anatomical, physiological and pathophysiological content of the object models explicit. In such an interdisciplinary context we chose to rely on a common integration framework provided by a foundational ontology, that facilitates the consistent integration of the various modules extracted from several existing ontologies, i.e. FMA, PATO, MPATH, RadLex and ChEBI. Emphasis is put on methodology for achieving this extraction and integration. The most salient aspects of the ontology are presented, especially the organization in model layers, as well as its use to browse and query the model repository.

2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), 2016

New horizons in x-ray imaging have been opened up with the emergence of energy-resolved photon co... more New horizons in x-ray imaging have been opened up with the emergence of energy-resolved photon counting detectors (PCDs). These include the ability to differentiate material components and estimate their equivalent thickness or relative ratio by processing a single shot acquisition image. However, such techniques require highly accurate images, especially for materials close in terms of attenuation. The presence of scattered radiation leads to a loss of contrast and, more importantly, a bias in radiographic material imaging and artefacts in cone-beam CT. The aim of the present study was to evaluate the performance gain in material imaging when a Partial Attenuation Spectral Scatter Separation Approach (PASSSA) is used. This evaluation was based on numerical simulations using Sindbad-SFFD. The comparison of water and bone thickness images acquired from scatter free, scatter corrupted and PASSSA-corrected images showed that the application of the considered correction method improved thickness estimation accuracy. The average relative thickness estimation error per pixel was reduced by around a factor of 4.7 for both water and bone images when comparing scatter corrupted and PASSSA-corrected cases.

The Krotos experience requires fast imaging (10 to 100 images/sec) of a dynamic process involving... more The Krotos experience requires fast imaging (10 to 100 images/sec) of a dynamic process involving highly attenuating corium (density 8) and detection of low density variations (distinction between water and steam), with millimetric spatial resolution. In response to this difficult problem, various solutions were devised and simulated. We will show that the only feasible option is to use a very high energy (8 MeV) and very powerful source (0.3 Gy/s), associated with a scintillator screen optically linked to a high sensitivity CCD camera. This solution has been validated in the experimental phase to ensure its performance: results confirm the possibility of monitoring with 10 images/sec with a single X flash per image. Introduction: The study of "serious accidents" involves imagining the case of a nuclear reactor core fusion: resulting from a cooling fault, all structures (mainly zircaloy) and nuclear fuel (in uranium oxide form, to which fission products are added) melt to ...

Anomaly Detection and Imaging with X-Rays (ADIX) II, 2017

X-ray diffraction is known to be an effective technique for illicit materials detection in baggag... more X-ray diffraction is known to be an effective technique for illicit materials detection in baggage screening, as it can reveal molecular structural information of any solid substances but also of liquids, aerosols and gels. Some X-ray diffraction systems using 2D pixelated spectrometric detectors, such as CdZnTe detectors, are then able to perform 3D baggage scanning in time compatible with bag throughput constraints of airports. However, X-ray diffraction systems designed for baggage screening generally suffer from poor photon count statistics and bad spatial resolution, because of the tight collimations and the small scattering angle. To improve these factors, techniques of sub-pixelation can be implemented in CdZnTe detectors. Indeed, sub-pixelation enables to open the collimation without angular resolution degradation and also to segment the inspected volume in several sub-volumes, inducing a better spatial resolution in the X-ray beam direction. In this paper, we present some experiments demonstrating the interest of sub-pixelation within CdZnTe detectors for X-ray diffraction imaging systems. In particular, an experimental demonstration is presented with a 2D XRD image of a realistic baggage performed with only one single pixel from our own CdZnTe based imager.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2017

Scattered radiation results in various undesirable effects in medical diagnostics, non-destructiv... more Scattered radiation results in various undesirable effects in medical diagnostics, non-destructive testing (NDT) and security x-ray imaging. Despite numerous studies characterizing this phenomenon and its effects, the knowledge of its behavior in the energy domain remains limited. The present study aims at summarizing some key insights on scattered radiation originating from the inspected object. In addition, various simulations and experiments with limited collimation on both simplified and realistic phantoms were conducted in order to study scatter behavior in multi-energy x-ray imaging. Results showed that the spectrum shape of the scatter component can be considered preserved in the first approximation across the image plane for various acquisition geometries and phantoms. The variations exhibited by the scatter spectrum were below 10% for most examined cases. Furthermore, the corresponding spectrum shape proved to be also relatively invariant for different experimental angular projections of one of the examined phantoms. The observed property of scattered radiation can potentially lead to the decoupling of spatial and energy scatter components, which can in turn enable speed ups in scatter simulations and reduce the complexity of scatter correction.

Physics in Medicine and Biology, 2016

Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon c... more Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon counting detectors enable the identification and quantification of individual materials comprising the inspected object. However, the approaches used for these operations require highly accurate x-ray images. The accuracy of the images is severely compromised by the presence of scattered radiation, which leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to experimentally evaluate a recently introduced partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. For this purpose, a prototype x-ray system was used. Several radiographic acquisitions of an anthropomorphic thorax phantom were performed. Reference primary images were obtained via the beam-stop (BS) approach. The attenuation images acquired from PASSSA-corrected data showed a substantial increase in local contrast and internal structure contour visibility when compared to uncorrected images. A substantial reduction of scatter induced bias was also achieved. Quantitatively, the developed method proved to be in relatively good agreement with the BS data. The application of the proposed scatter correction technique lowered the initial normalized root-mean-square error (NRMSE) of 45% between the uncorrected total and the reference primary spectral images by a factor of 9, thus reducing it to around 5%.

Physics in Medicine and Biology, 2016

X-ray imaging coupled with recently emerged energy-resolved photon counting detectors provides th... more X-ray imaging coupled with recently emerged energy-resolved photon counting detectors provides the ability to differentiate material components and to estimate their respective thicknesses. However, such techniques require highly accurate images. The presence of scattered radiation leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in computed tomography (CT). The aim of the present study was to introduce and evaluate a partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. This evaluation was carried out with the aid of numerical simulations provided by an internal simulation tool, Sindbad-SFFD. A simplified numerical thorax phantom placed in a CT geometry was used. The attenuation images and CT slices obtained from corrected data showed a remarkable increase in local contrast and internal structure detectability when compared to uncorrected images. Scatter induced bias was also substantially decreased. In terms of quantitative performance, the developed approach proved to be quite accurate as well. The average normalized root-mean-square error between the uncorrected projections and the reference primary projections was around 23%. The application of PASSSA reduced this error to around 5%. Finally, in terms of voxel value accuracy, an increase by a factor >10 was observed for most inspected volumes-of-interest, when comparing the corrected and uncorrected total volumes.

AIP Conference Proceedings, 2009

ABSTRACT Code Validation is a permanent concern in computer modelling, and has been addressed rep... more ABSTRACT Code Validation is a permanent concern in computer modelling, and has been addressed repeatedly in eddy current and ultrasonic modeling. A good benchmark problem is sufficiently simple to be taken into account by various codes without strong requirements on geometry representation capabilities, focuses on few or even a single aspect of the problem at hand to facilitate interpretation and to avoid that compound errors compensate themselves, yields a quantitative result and is experimentally accessible. In this paper we attempt to address code validation for one aspect of radiographic modeling, the scattered radiation prediction. Many NDT applications can not neglect scattered radiation, and the scatter calculation thus is important to faithfully simulate the inspection situation. Our benchmark problem covers the wall thickness range of 10 to 50 mm for single wall inspections, with energies ranging from 100 to 500 keV in the first stage, and up to 1 MeV with wall thicknesses up to 70 mm in the extended stage. A simple plate geometry is sufficient for this purpose, and the scatter data is compared on a photon level, without a film model, which allows for comparisons with reference codes like MCNP. We compare results of three Monte Carlo codes (McRay, Sindbad and Moderato) as well as an analytical first order scattering code (VXI), and confront them to results obtained with MCNP. The comparison with an analytical scatter model provides insights into the application domain where this kind of approach can successfully replace Monte-Carlo calculations.

The application of a radiographic inspection procedure in nuclear NDE requires a formal demonstra... more The application of a radiographic inspection procedure in nuclear NDE requires a formal demonstration of the procedure's capability to detect the supposed defects. The French RSE-M code authorizes different means to achieve the performance demonstration, such as experience feedback , experiments on mock-ups and computer modeling, which are often employed in combination. To enable performance demonstration, a new gamma and X-Ray simulation module has been integrated to the CIVA software platform and completes the already available UT and ET modules. This module is based on a combination of NDT radiographic simulation modules developed at the CEA LETI and at EDF R&D. Direct radiation is calculated from an analytical approach (ray tracer and Beer-Lambert law for the attenuation) while the scattered radiation is simulated by Monte-Carlo modeling. In this context CIVA X-Ray enables simulating a realistic and complex inspection configuration taking into account the most influential parameters of a radiographic inspection. In this paper we illustrate how CIVA-RX addresses the specific requirements of nuclear NDE on radiographic modeling, present examples from three typical application domains, and elaborate on the assessment of an indication's visibility. SPECIFIC REQUIREMENTS ON COMPUTER MODELING OF RADIOGRAPHIC INSPECTIONS OF NUCLEAR COMPONENTS Radiographic inspection as a non destructive inspection technique is commonly used in numerous application domains, such as aerospace, chemistry, oil/off shore, archeology and nuclear power plants, each of which has specific requirements which must be addressed individually. As opposed to aerospace applications, the components inspected in nuclear applications have two specific properties: More info about this article: http://www.ndt.net/?id=8821 More info about this article:

Nondestructive Testing of Materials and Structures, 2011

Computer modelling of non-destructive testing methods has come a long way from the beginnings in ... more Computer modelling of non-destructive testing methods has come a long way from the beginnings in the mid 90s to today. Radiographic modelling for components with higher wall thicknesses, as they are typical for nuclear applications, must include precise predictions of scattered radiation and its impact in terms of contrast reduction. Dedicated or general purpose Monte Carlo methods with the ability to calculate higher order scattering events are the state of the art for these applications. Aerospace applications, on the other hand, have stronger requirements on the modelling code’s capabilities to import complex CAD geometries, and can benefit from faster analytical scatter models, limited to first or second order scattering events. Similar distinctions can be made for the various approaches proposed to accurately model geometrical and film unsharpness, film granularity, film responses, film/foil cartridges and photon noise. This article presents a state-of-the-art review of radiographic modelling from the perspective of two important application domains with very different requirements, nuclear and aerospace.

AIP Conference Proceedings, 2010

ABSTRACT Code Validation is a permanent concern in computer simulation, and has been addressed re... more ABSTRACT Code Validation is a permanent concern in computer simulation, and has been addressed repeatedly in eddy current and ultrasonic modelling. A good benchmark problem is sufficiently simple to be taken into account by various codes without strong requirements on geometry representation capabilities, focuses on few or even a single aspect of the problem at hand to facilitate interpretation and to avoid that compound errors compensate themselves, yields a quantitative result and is experimentally accessible. In this paper we attempt to address code validation for one aspect of radio-graphic modelling, the scattered radiation prediction. An update of the results of the 2008 benchmark is presented. Additionally we discuss the extension of this benchmark on the lower energy part for 60 and 80 keV as well as for higher energies up to 10 MeV to study the contribution of pair production. Of special interest will be the primary radiation (attenuation law as reference), the total scattered radiation, the relative contribution of scattered radiation separated by order of scatter events (1st, 2nd, ..., 20th), and the spectrum of scattered radiation. We present the results of three Monte Carlo codes (MC-Ray, Sindbad and Moderato) as well as an analytical first order scattering code (VXI) and compare to MCNP as reference. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints

A new gamma and X-Ray simulation module has been integrated to the CIVA software and completes th... more A new gamma and X-Ray simulation module has been integrated to the CIVA software and completes the already available UT and ECT modules. This module is based on a combination of NDT radiographic modules developed at the CEA LETI and at EDF R&D. Direct radiation is calculated from an analytical appro ach (ray tracer and Beer-Lambert law for the attenuation) while the scattered radiation is s imulated by Monte-Carlo modelling. Different types of sources, gamma or X-rays, and differ ent detectors can be simulated. The X ray module uses the same dedicated Graphical User Interfa ce mutual to UT and ECT techniques. It helps to simulate control of specimens whe re the geometry can be imported from a CAD tool and also to put in evidence the presence of defects (with canonical geometries or also defined from a CAD tool). In this article, after a description of the different models used, the X-Ray simulation possibilities are illustrated on different practical ap plications.

2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2014

New horizons in x-ray radiography and computed tomography (CT) have been opened up with the emerg... more New horizons in x-ray radiography and computed tomography (CT) have been opened up with the emergence of energy resolved x-ray imaging. This includes the ability to differentiate material components and estimate their equivalent thickness or relative ratio by processing a single shot acquisition image. However, such techniques require highly accurate images, especially for materials close in terms of attenuation. The presence of scattered radiation leads to a loss of contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to evaluate the disturbance caused by scatter on multi-energy imaging, more precisely, on a material decomposition approach commonly used in radiography or CT. This evaluation was based on numerical simulations using Sindbad-SFFD. Results showed a significant impact of scattered radiation on quantification accuracy for a simplified thorax-sized numerical phantom with an average error of 157.1% and 74.1% for cortical bone and water thickness, respectively. When only 10% of scatter was considered the error still remained significant: 35.1% and 17.5% for cortical bone and water thickness, respectively. The study concludes that a scatter correction method should be performed prior to any material decomposition, if one aims to benefit from energy resolved data in an uncollimated geometry.

2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515)

A fully three-dimensional model of a semiconductor gamma-ray detector is presented. The model tak... more A fully three-dimensional model of a semiconductor gamma-ray detector is presented. The model takes into account the gamma-ray and charge collection physical phenomena involved in the detection process and models the readout electronic response and noise. The model successively involves the Monte Carlo simulation of the photon transport, the finite element transient computation of the adjoint transport equation, and the

Backscatter X-ray technique is particularly convenient for the inspection of single-sided access ... more Backscatter X-ray technique is particularly convenient for the inspection of single-sided access objects, in order to detect subsurface defects or control subsurface layers thickness. This well known technique can benefit today from recent developments in detectors technology. Backscatter technique requires many parameters: relative geometry of source, detector and object, and associated collimation. In order to help the design of backscatter systems, we have developed a software simulation tool, able to predict the backscatter signals for given systems and objects. Theoretically, such a simulation should be performed based on Monte Carlo code to manage multiple scatter interactions. We propose a version based on analytical computation, allowing fast simulation, and a modified one using partially a Monte Carlo code, if more accuracy is required. Experimental measurements are compared to simulation. The proposed tool can also help the interpretation and analysis of backscatter signal...

SPIE Proceedings, 2003

ABSTRACT Osteoporosis is a disease characterized by a decrease of bone mineral density as well as... more ABSTRACT Osteoporosis is a disease characterized by a decrease of bone mineral density as well as by architecture modification leading to an increase of fracture risk. This paper is part of study investigating the possibility to extract some structural parameters quantifying trabecular bone architecture from radiographies realized in vivo. The first step of the study is the definition of optimum radiographic conditions (X-ray spectrum, detector) as well as the development of adapted image processing tools to extract relevant indexes characterizing architecture. Therefore a simulation process computing synthetic radiographies from trabecular bone samples has been developed. This process is done in three distinct steps: (1) Computation of a very high spatial resolution 3D muCT volume of a human trabecular bone sample from a series of acquisitions with a microtomography system using synchrotron radiation. (2) Transformation of the muCT volume in a materials voxel volume. (3) Simulation of the radiography projection by using the X-ray radiographic simulation software Sindbad. The simulation software provides a lot of parameters which can be easily modified (spectra, materials, geometry, detector...) so that its use for an optimisation purpose is very practical. Comparison of simulated and experimental radiographies performed under synchrotron radiation microtomography configuration validates the accuracy of our simulation process. Simulated radiographs under several clinical conditions are also presented.

Proceedings - 2012 IEEE 2nd Conference on Healthcare Informatics, Imaging and Systems Biology, HISB 2012, 2012

This paper describes the creation of a comprehensive conceptualization of object models used in m... more This paper describes the creation of a comprehensive conceptualization of object models used in medical image simulation, suitable for major imaging modalities and simulators. The goal is to create an application ontology that can be used to annotate the models in a repository integrated in the Virtual Imaging Platform (VIP), to facilitate their sharing and reuse. Annotations make the anatomical, physiological and pathophysiological content of the object models explicit. In such an interdisciplinary context we chose to rely on a common integration framework provided by a foundational ontology, that facilitates the consistent integration of the various modules extracted from several existing ontologies, i.e. FMA, PATO, MPATH, RadLex and ChEBI. Emphasis is put on methodology for achieving this extraction and integration. The most salient aspects of the ontology are presented, especially the organization in model layers, as well as its use to browse and query the model repository.

2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), 2016

New horizons in x-ray imaging have been opened up with the emergence of energy-resolved photon co... more New horizons in x-ray imaging have been opened up with the emergence of energy-resolved photon counting detectors (PCDs). These include the ability to differentiate material components and estimate their equivalent thickness or relative ratio by processing a single shot acquisition image. However, such techniques require highly accurate images, especially for materials close in terms of attenuation. The presence of scattered radiation leads to a loss of contrast and, more importantly, a bias in radiographic material imaging and artefacts in cone-beam CT. The aim of the present study was to evaluate the performance gain in material imaging when a Partial Attenuation Spectral Scatter Separation Approach (PASSSA) is used. This evaluation was based on numerical simulations using Sindbad-SFFD. The comparison of water and bone thickness images acquired from scatter free, scatter corrupted and PASSSA-corrected images showed that the application of the considered correction method improved thickness estimation accuracy. The average relative thickness estimation error per pixel was reduced by around a factor of 4.7 for both water and bone images when comparing scatter corrupted and PASSSA-corrected cases.

The Krotos experience requires fast imaging (10 to 100 images/sec) of a dynamic process involving... more The Krotos experience requires fast imaging (10 to 100 images/sec) of a dynamic process involving highly attenuating corium (density 8) and detection of low density variations (distinction between water and steam), with millimetric spatial resolution. In response to this difficult problem, various solutions were devised and simulated. We will show that the only feasible option is to use a very high energy (8 MeV) and very powerful source (0.3 Gy/s), associated with a scintillator screen optically linked to a high sensitivity CCD camera. This solution has been validated in the experimental phase to ensure its performance: results confirm the possibility of monitoring with 10 images/sec with a single X flash per image. Introduction: The study of "serious accidents" involves imagining the case of a nuclear reactor core fusion: resulting from a cooling fault, all structures (mainly zircaloy) and nuclear fuel (in uranium oxide form, to which fission products are added) melt to ...

Anomaly Detection and Imaging with X-Rays (ADIX) II, 2017

X-ray diffraction is known to be an effective technique for illicit materials detection in baggag... more X-ray diffraction is known to be an effective technique for illicit materials detection in baggage screening, as it can reveal molecular structural information of any solid substances but also of liquids, aerosols and gels. Some X-ray diffraction systems using 2D pixelated spectrometric detectors, such as CdZnTe detectors, are then able to perform 3D baggage scanning in time compatible with bag throughput constraints of airports. However, X-ray diffraction systems designed for baggage screening generally suffer from poor photon count statistics and bad spatial resolution, because of the tight collimations and the small scattering angle. To improve these factors, techniques of sub-pixelation can be implemented in CdZnTe detectors. Indeed, sub-pixelation enables to open the collimation without angular resolution degradation and also to segment the inspected volume in several sub-volumes, inducing a better spatial resolution in the X-ray beam direction. In this paper, we present some experiments demonstrating the interest of sub-pixelation within CdZnTe detectors for X-ray diffraction imaging systems. In particular, an experimental demonstration is presented with a 2D XRD image of a realistic baggage performed with only one single pixel from our own CdZnTe based imager.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2017

Scattered radiation results in various undesirable effects in medical diagnostics, non-destructiv... more Scattered radiation results in various undesirable effects in medical diagnostics, non-destructive testing (NDT) and security x-ray imaging. Despite numerous studies characterizing this phenomenon and its effects, the knowledge of its behavior in the energy domain remains limited. The present study aims at summarizing some key insights on scattered radiation originating from the inspected object. In addition, various simulations and experiments with limited collimation on both simplified and realistic phantoms were conducted in order to study scatter behavior in multi-energy x-ray imaging. Results showed that the spectrum shape of the scatter component can be considered preserved in the first approximation across the image plane for various acquisition geometries and phantoms. The variations exhibited by the scatter spectrum were below 10% for most examined cases. Furthermore, the corresponding spectrum shape proved to be also relatively invariant for different experimental angular projections of one of the examined phantoms. The observed property of scattered radiation can potentially lead to the decoupling of spatial and energy scatter components, which can in turn enable speed ups in scatter simulations and reduce the complexity of scatter correction.

Physics in Medicine and Biology, 2016

Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon c... more Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon counting detectors enable the identification and quantification of individual materials comprising the inspected object. However, the approaches used for these operations require highly accurate x-ray images. The accuracy of the images is severely compromised by the presence of scattered radiation, which leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to experimentally evaluate a recently introduced partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. For this purpose, a prototype x-ray system was used. Several radiographic acquisitions of an anthropomorphic thorax phantom were performed. Reference primary images were obtained via the beam-stop (BS) approach. The attenuation images acquired from PASSSA-corrected data showed a substantial increase in local contrast and internal structure contour visibility when compared to uncorrected images. A substantial reduction of scatter induced bias was also achieved. Quantitatively, the developed method proved to be in relatively good agreement with the BS data. The application of the proposed scatter correction technique lowered the initial normalized root-mean-square error (NRMSE) of 45% between the uncorrected total and the reference primary spectral images by a factor of 9, thus reducing it to around 5%.

Physics in Medicine and Biology, 2016

X-ray imaging coupled with recently emerged energy-resolved photon counting detectors provides th... more X-ray imaging coupled with recently emerged energy-resolved photon counting detectors provides the ability to differentiate material components and to estimate their respective thicknesses. However, such techniques require highly accurate images. The presence of scattered radiation leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in computed tomography (CT). The aim of the present study was to introduce and evaluate a partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. This evaluation was carried out with the aid of numerical simulations provided by an internal simulation tool, Sindbad-SFFD. A simplified numerical thorax phantom placed in a CT geometry was used. The attenuation images and CT slices obtained from corrected data showed a remarkable increase in local contrast and internal structure detectability when compared to uncorrected images. Scatter induced bias was also substantially decreased. In terms of quantitative performance, the developed approach proved to be quite accurate as well. The average normalized root-mean-square error between the uncorrected projections and the reference primary projections was around 23%. The application of PASSSA reduced this error to around 5%. Finally, in terms of voxel value accuracy, an increase by a factor >10 was observed for most inspected volumes-of-interest, when comparing the corrected and uncorrected total volumes.

AIP Conference Proceedings, 2009

ABSTRACT Code Validation is a permanent concern in computer modelling, and has been addressed rep... more ABSTRACT Code Validation is a permanent concern in computer modelling, and has been addressed repeatedly in eddy current and ultrasonic modeling. A good benchmark problem is sufficiently simple to be taken into account by various codes without strong requirements on geometry representation capabilities, focuses on few or even a single aspect of the problem at hand to facilitate interpretation and to avoid that compound errors compensate themselves, yields a quantitative result and is experimentally accessible. In this paper we attempt to address code validation for one aspect of radiographic modeling, the scattered radiation prediction. Many NDT applications can not neglect scattered radiation, and the scatter calculation thus is important to faithfully simulate the inspection situation. Our benchmark problem covers the wall thickness range of 10 to 50 mm for single wall inspections, with energies ranging from 100 to 500 keV in the first stage, and up to 1 MeV with wall thicknesses up to 70 mm in the extended stage. A simple plate geometry is sufficient for this purpose, and the scatter data is compared on a photon level, without a film model, which allows for comparisons with reference codes like MCNP. We compare results of three Monte Carlo codes (McRay, Sindbad and Moderato) as well as an analytical first order scattering code (VXI), and confront them to results obtained with MCNP. The comparison with an analytical scatter model provides insights into the application domain where this kind of approach can successfully replace Monte-Carlo calculations.