A multi-resolution image reconstruction method in X-ray computed tomography

International audienceWe propose a multiresolution X-ray imaging method designed for non-destructive testing/ evaluation (NDT/NDE) applications which can also be used for small animal imaging studies. Two sets of projections taken at different magnifications are combined and a multiresolution image is reconstructed. A geometrical relation is introduced in order to combine properly the two sets of data and the processing using wavelet transforms is described. The accuracy of the reconstruction procedure is verified through a comparison to the standard filtered backprojection (FBP) algorithm on simulated data

Parallélisation sur GPU d'un algorithme de reconstruction 3D bayésien en tomographie X.

An important number of image reconstruction algorithms are implemented in the literature on X-ray CT (Computed Tomography) data. The main family of methods are analytical, mainly filtered backprojection which are implemented generally in medical imaging for their fast reconstruction time. The limits of these methods appear when the number of projections is small, and/or not equidistributed around the object. In this specific context, iterative algebraic methods are implemented. A great number of them are mainly based on least square criterion. We propose a regularized version of iterative algorithms to improve results. The main problem that appears when using iterative algebraic methods is the computation time and especially for projection and backprojection steps. We propose to implement some steps of the iterations on GPU hardware. We present an original method based on a Bayesian statistical method for 3D tomographic reconstructions. The main interest is to apply it in a context of non-consistent data sets, for example with a small number of projections. We show a good quality of results and a significant speed up of the calculation with GPU implementation

Suivi dynamique des mouvements fluides par appariement de squelettes morphologiques linéarisés

Nous proposons un algorithme permettant la prédiction et le suivi de déformations fluides complexes (non modélisables par des approches paramétriques), donnant lieu éventuellement à des changements de topologie, à partir d'une mise en correspondance des squelettes morphologiques linéarisés. L'approche squelette permet de traiter conjointement les phénomènes d'advection (déplacement) par le corps du squelette et ceux de convection (inflation/déflation) par les rayons associés à leur axe médian. Le squelette est calculé de façon robuste par une méthode récemment développée à partir de la carte de distance de Danielson. L'appariement des squelettes linéarisés est obtenu par un algorithme récursif de relaxation/labelisation issu des travaux de Zucker. Du champ de vecteurs lacunaire d'appariement est interpolé un champ dense par filtrage gaussien, qui va permettre la prédiction des déformations fluides en l'appliquant aux squelettes initiaux et en reconstruisant les formes à partir des squelettes ainsi transformés. L'algorithme est illustré dans le cas applicatif de suivi de fouillis radar

Study of the behavior of vapor fraction in a turbopump inducer using an X-ray measurement technique

International audienceThis work intended to study the behavior of the instantaneous vapor fraction in the turbopump inducer of a liquid propellant rocket engine. Experimentations held on an experimental pump test facility and cavitation was attained by reducing the inlet pressure in the machine while maintaining constant the inducer rotational speed. Measurements of vapor fraction through the rotating inducer were achieved by means of an X-ray-based system. The system exerted an industrial X-ray generator and 10 collimated scintillation detectors. Detectors were functioning in current mode thus permitting an acquisition at 5 kHz for each detector. A reference X-ray detector situated between the X-ray generator and the machine permitted the treatment of X-ray beam energy fluctuations related to industrial generators. Acquisitions were performed in three axial positions on the inducer. For each measurement position, three cavitation sequences with different flow rate conditions ($Q/Q_n$ = 0.9, 1, 1.1, where $Q_n$ is the nominal flow rate) were accomplished. Each cycle is performed by decreasing gradually the pressure while maintaining an imposed rotational speed of 4,000 rpm. Each test is constituted of 10 pressure points varying from 2.40 to 0.48 bars representing a complete cavitation sequence. X-ray acquisition was performed for each pressure point, and it was carried out for 10 s thus corresponding to 667 tours of the inducer. Vapor fraction was determined instantaneously thus showing the applicability and the precision of the method in such measurements despite of the geometry and rotation speed constraints. Consequently a quantitative and qualitative evaluation of the vapor fraction is presented. Results show that the vapor distribution is well related to cavitation development on the blades of the inducer for steady cavitation condition

Reconstruction in vivo de l'image 3D de la dose déposée lors d'une irradiation en radiothérapie

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Bayesian data fusion and inversion in X-ray multi-energy computed tomography

International audienc

FEDSM2005-77371 DYNAMIC VAPOUR FRACTION MEASUREMENT IN TURBOPUMP INDUCERS BY X-RAYS FEDSM2005-77371

ABSTRACT This work intended to evaluate the instantaneous vapour fraction in the turbo-pump inducer of a liquid propellant rocket engine. Experimentations held on an experimental pump test facility and cavitation was attained by reducing the inlet pressure in the machine while maintaining constant the inducer rotational speed. Measurements of vapour fraction through the rotating inducer were achieved by means of an x-ray-based system. The system exerted an industrial x-ray generator and 10 collimated scintillation detectors. Detectors were functioning in current mode thus permitting an acquisition at 5 kHz for each detector. A reference x-ray detector situated between the x-ray generator and the machine permitted the treatment of x-ray beam energy fluctuations related to industrial generators INTRODUCTION Conquering the space solicits industry to contrive launchers with more and more efficiency capable of transmitting more loads to space. Intending to procure in useful load, constructors are urged to run down the thickness of fuel tanks while reducing the drain pressure of the pumps. In order to thrust combustibles while pushing ahead, launchers engage high flow turbo pumps. Being constrained by the size, the inducer should rotate at a very high speed to ensure a pressure gradient at constant flow rate

Dynamic Localization of Vapour Fraction in Ariane 5 Inducer by X-Rays Tomography

An experimental study of the instantaneous local behavior of cavitation in turbo-pump inducers is presented in this article. Experiments held on a hydrodynamic facility equipped with an Ariane 5 inducer permitted achieving the aim. Cavitation is attained by reducing the pressure in a turbo machine having an inducer rotating at 4000 rpm. An X-ray tomography system developed specially for this aim, was used to measure the cavitation. The system employed an industrial X-ray generator and scintillation detectors. The generator/detectors system was fixed while the inducer was rotating. Vapor fraction was determined instantaneously, which confirms the applicability and the precision of the method in such type of measurements despite the constraints imposed by the geometry and the rotation speed. The dense composition of the system components introduced difficulties in the measurement especially at the inducer axis. However, prior information concerning the vapor regime as well as its stationary behavior in certain time intervals helped overcome this problem. Consequently a quantitative and qualitative evaluation of the vapor fraction is obtained. Results show a cavitation regime mostly synchronous with the rotation of the inducer thus permitting the use of tomographic reconstruction for the localization of vapor in the machine. An algebraic reconstruction algorithm (ML-EM) was used to achieve image reconstruction