Utilisation d'un modele d'objet en reconstruction 3D

Nous décrivons un système de reconstruction 3D pour la tomographie en transmission intégrant l'algorithme RADON développé au LETI et l'utilisation de connaissances a priori sous forme d'un modèle 3D de l'objet à reconstruire. Les objets que nous cherchons à reconstruire sont naturellement bien contrastés. Le modèle markovien choisi nous permet de mieux préserver les frontières naturelles de l'objet alors que les méthodes classiques ont tendance à lisser les transitions

Cone beam 3D reconstruction with double circular trajectory

In x-ray cone beam tomography the only planar source trajectory which do not produce incomplete data is the infinite line. This kind of source trajectory is not experimentally doable. To ensure a complete data acquisition with cone beam radiographs, a set of non planar trajectory has been studied. Among the trajectories proposed in the literature a simple one is the set of 2 circular trajectories with intersection of the two circular trajectories with intersection of the two trajectory axis. The angle between the two axis is related to the maximum aperture of the cone beam. We propose here an exact method to perform this reconstruction using the 3D radon transform of the object. The modulation transfer function (MTF) of this algorithm remain identical to the MTF on the central slice of reconstruction with single circular trajectory. The density relative mean square error stays within 2% for an aperture of {plus minus}30{degree}. With single circular trajectory the relative mean square error may reach 20% at the same aperture. With double circular trajectory, horizontal artifacts are almost suppressed. 12 refs., 5 figs

X-Ray Cone Beam Tomography with Two Tilted Circular Trajectories

Recently 3-D cone-beam tomography has become of interest for the nondestructive evaluation of advanced materials. The main field of application in nondestructive testing is the evaluation of structural ceramics. Study of such materials implies high density resolution and high sensitivity to cracks. In fact, with a single circular source trajectory, when the cone-beam aperture increases, density is underestimated and cone shaped artifacts may appear at interfaces in the sample even at relatively small aperture [1–3]. These artifacts limit the thickness we can examine with a planar source trajectory. To maintain optimal reconstruction accuracy with a circular source trajectory, the angular aperture must remain within ±10°. However Kudo and Saito [4] showed that this limit can be slightly overcome by using a special interpolation of the shadow area. But to examine greater thicknesses and to maintain resolution, we must widen the cone-beam aperture thereby decreasing accuracy. To overcome these aperture limitations, Tuy [5] introduced the double circular source trajectory idea.</p

Recentes evolutions de la tomographie 3D en geometrie conique

La tomographie 3D en géométrie conique définit un mode d'acquisition performant. Notre analyse théorique de la reconstruction repose sur le calcul et l'inversion de la dérivée première de la transformée de Radon. Nous décrivons ici les récentes évolutions de nos travaux, à savoir le développement du logiciel RADON et son optimisation, l'étude d'un protocole d'analyse de la FTM et l'extension de notre algorithme à deux trajectoires d'acquisition circulaires inclinées

Utilisation d'un modele d'objet en reconstruction 3D

communication a : conference of the research and studies group on signal processing, Juan-les-Pins (FR), 16-20 Sep 1991SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RM 1097 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

High-throughput sample handling and data collection at synchrotrons: embedding the ESRF into the high-throughput gene-to-structure pipeline.

An automatic data-collection system has been implemented and installed on seven insertion-device beamlines and a bending-magnet beamline at the ESRF (European Synchrotron Radiation Facility) as part of the SPINE (Structural Proteomics In Europe) development of an automated structure-determination pipeline. The system allows remote interaction with beamline-control systems and automatic sample mounting, alignment, characterization, data collection and processing. Reports of all actions taken are available for inspection via database modules and web services