Medicine counterfeiting is a health and economic problem that the pharmaceutical field has to deal with. X-ray diffraction, known to be very specific in characterizing the structure of molecules, can be an interesting technique for detecting counterfeit drugs without having to take them out of their packaging.
In this context, we have developed a relatively compact system which combines the use of an integrated X-ray source and a compact high-performance CdZnTe imager. This system has been tested on several drugs and has shown its ability to easily detect counterfeit pharmaceuticals in their packaging in less than a few minutes.
X-ray diffraction (XRD) is proven to be an effective technique for baggage screening, as it can reveal inter- and intramolecular structural information of any solid substances (mostly polycrystalline), but also of liquids, aerosols and gels. The introduction of 2D pixelated energy resolved detectors, such as CdZnTe detectors, makes now possible the development of Energy Dispersive XRD (EDXRD) systems able to perform rapid in situ 3D baggage scanning. However, the EDXRD technique requires to fix the scattering angle to few degrees with very thick collimations, which induces lack of sensitivity and spatial resolution. It is then a question of proposing technological, architectural and algorithmic solutions to improve and find the best compromise between spatial resolution, power of discrimination and inspection speed. The CEA-LETI has designed CdZnTe based energy resolved detectors in which some specific detector-level signal processing are implemented to optimize both energy and spatial resolution thanks to subpixel positioning. Subpixel positioning enables to significantly improve both angular and spatial resolution in an EDXRD system. We implemented an EDXRD system using such a detection module coupled to a multiplexed secondary collimation, in which each physical pixel inspects the object at 4 or 5 different points. The sensitivity is more than four times better compared to a parallel collimation. Some specific iterative inversion algorithms reconstruct the diffraction signatures of the materials, even when they are close together as inside a baggage. Material discrimination performance limits were explored for several objects scenarios and various levels of photon statistics.
Mammography is the first tool in breast cancer diagnosis. Its contrast relies on the difference of X-Ray attenuation in healthy and diseased tissues, which is quite limited. This leads to frequent false-positive or inconclusive results and requires further testing. X-Ray Diffraction provides information about molecular structure and can differentiate between healthy and cancerous breast tissues. It can thus be used in synergy with existing imaging methods to provide complementary diagnosis-relevant insight. We present a novel geometry of such an imaging system and its validation on a breast phantom composed of olive oil and beef muscle, imitating respectively the molecular structure of healthy and cancerous breast tissue. Our system combines energy-dispersive and angle-dispersive X-Ray diffraction by means of an energy-resolved CdZnTe detector and a multi-slit collimation in order to achieve depth-resolved imaging. The position of the tube with beef muscle inside the oil was varied in this experiment. The obtained results are satisfactory regarding the estimated position of the tube which is very promising for future ex-vivo experiments on human breast tissue samples. Further investigations are carried out on dose reduction and reliable classification algorithms in order to prepare this method for clinical applications.
False-positive mammography results in breast cancer diagnosis can lead to unnecessary biopsies which are invasive and time-consuming. X-Ray Diffraction (XRD) has the potential of providing diagnosis-relevant information and thus can be used after a mammography to verify its results and possibly avoid needless biopsy. We present an energy-dispersive X-Ray Diffraction (EDXRD) system and data analysis method which allowed us to characterize healthy and cancerous mice mammary glands ex-vivo. Our technique showed decent glad localization along the z-axis as well as scatter signatures coherent with ones previously described in literature. We used an in-house spatially resolved CdZnTe detector, and a subpixelation technique which enhances spatial resolution. Acquisition time and dose delivered are to be optimized yet, however our results demonstrate the potential of EDXRD systems for depth-resolved breast imaging. Different geometries and processing algorithms are currently being investigated in the development of a future EDXRD clinical system for breast cancer diagnosis.
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.
KEYWORDS: Monte Carlo methods, Sensors, Solid modeling, Computer aided design, Computer simulations, 3D modeling, Optical simulations, Data modeling, Lead, Photon transport
The use of focused anti-scatter grids on digital radiographic systems with two-dimensional detectors produces acquisitions with a decreased scatter to primary ratio and thus improved contrast and resolution. Simulation software is of great interest in optimizing grid configuration according to a specific application. Classical simulators are based on complete detailed geometric descriptions of the grid. They are accurate but very time consuming since they use Monte Carlo code to simulate scatter within the high-frequency geometric description of the grid. We propose a new practical method which couples an analytical simulation of the grid interaction with a radiographic system simulation program. First, a two dimensional matrix of probability depending on the grid is created offline, in which the first dimension represents the angle of impact with respect to the normal to the grid lines and the other the energy of the photon. This matrix of probability is then used by the Monte Carlo simulation software in order to provide the final x-rays scatter flux image. To evaluate the gain of CPU time, we define the increasing factor as the increase of CPU time of the simulation with as or without the grid. Increasing factors were calculated with the new model and with classical methods representing the grid with a Computed-Aided Designed (CAD) model. With this new method, increasing factors are shortened by three to four orders of magnitude.
Although the diagnosis of osteoporosis is mainly based on Dual X-ray Absorptiometry, it has been shown that trabecular bone micro-architecture is also an important factor in regards of fracture risk, which can be efficiently assessed in vitro using three-dimensional x-ray microtomography (μCT). In vivo, techniques based on high-resolution s-ray radiography associated to texture analysis have been proposed to investigate bone micro-architecture, but their relevance for giving pertinent 3D information is unclear. The purpose of this work was to develop a method for evaluating the relationships betweeen 3D micro-architecture and 2D texture parameters, and optimizing the conditions for radiographic imaging. Bone sample images taken from cortical to cortical were acquired using 3D-synchrotron x-ray μCT at the ESRF. The 3D digital imagees were further used for two purposes: 1) quantification of three-dimensional bone micro-architecture, 2) simulation of realistic x-ray radiographs under different acquisition conditions. Texture analysis was then applied to these 2D radiographs using a large variety of methods (co-occurence, spectrum, fractal...). First results of the statistical analysis between 2D and 3D parameters allowed identfying the most relevant 2D texture parameters.
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 μCT volume of a human trabecular bone sample from a series of acquisitions with a microtomography system using synchrotron radiation. (2) Transformation of the μCT 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.
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