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During knee arthroplasty, autologous blood donation is frequently used as an alternative to homologous blood transfusion. The hemoglobin level determines the organism answer to the anemia induced by the iteratives phlebotomies. We reviewed retrospectively 140 patients to correlate the hemoglobin levels before the predonations, pre- and postoperatively. In our series, the hemoglobin thresholds to evaluate the risks for an allo- or autotransfusion are consistent with previous findings. We set up a transfusional program for the patient undergoing knee arthroplasty.

The goal of this paper is to improve the determination of a target zone located in a slowly laterally varying background, by jointly inverting PP and PS waves available in prestack time migrated multicomponent data, while taking into account a priori information (well log data, geological knowledge...) in the inversion process: an optimal elastic model is estimated together with an optimal correspondence between PP and PS events. The methodology and results are illustrated on a 2D realistic synthetic example.

This paper presents an exhaustive time-lapse feasibility study where synthetic pre-stack seismic data are computed as function of reservoir production along elapsed time, and interpreted in a qualitative and quantitative ways. Geological model, based on a real gas storage site belonging to Gaz de France, is described in terms of lithofacies and converted to elastic models through elapsed time by using results of reservoir simulation together with a petroacoustic database. Two types of modeling (1D convolution and 3D fullwave) have been performed to obtain pre-stack data. Pre-stack joint inversion has next be used to derive P and S impedance cubes. Quantitative and qualitative interpretation conducted on both synthetic cubes and derived impedances enhance the lack of additional information given by the angle dimension and S-impedance in this particular case. Encouraging results come from the very good estimation of gas in place that can be obtained from P-impedance.

Prestack linearized elastic inversion is an advanced approach for reservoir characterization compared to conventional AVO methods. The elastic parameters estimated at the reservoir level are a potential source of information on lithological, petrophysical and fluid variations. This paper develops a two-component prestack linearized elastic inversion which allows to determine a 2D elastic target zone embedded in an almost laterally invariant elastic medium. The interest of accounting for the two components in the inversion process is investigated on simple examples (scattering point, isolated reflector), then on a realistic synthetic example built from a North sea field. The elastic parameters obtained by inversion of the realistic case are interpreted in terms of reservoir properties in order to evaluate the contribution of the proposed method to reservoir characterization.

For a realistic geological model a 2D numerical elastic modeling is carried out. The objectives is, first, a better understanding of the information content of reflection seismic data and, second, to provide synthetic data for testing and evaluating the efficiency of processing and inversion techniques under known conditions. Of particular interest are the small-scale heterogeneities in view of reservoir delineation and characterization. The geologic model is constructed from the Campanian cross-section of the Mesa Verde outcrop (Colorado, USA). A subsurface seismic model buried in a 1D background medium is defined from the 2D Mesa Verde geologic model by assigning P-wave and S-wave velocities and densities to each geologic facies. This seismic model is used as input for a fully elastic seismic simulating a realistic marine survey of 280 shots. The synthetic seismograms are calculated by a finite-difference method. The data are processed in a conventional way; then a target-related post-processing is performed including stratigraphic inversion. Finally, a geologic significance is given to waveform and amplitude variations in the estimated P-impedances.

There has been a considerable amount of work to solve the linearized inversion of seismic data (Ikelle et al.,1988, Beydoun et Mendes, 1989, Lambare et al., 1992, Jin et al., 1992). We have proposed a 2D target-oriented prestack linearized inversion techniques using finite differences (Mace et al., 1989, Bourgeois et al., 1993). It considers that the actual medium is formed by small perturbations from an input plane stratified (1D) reference model, such that the Born approximation holds.

Over the past decade, theory and experiments have shown that changes of reflection amplitude with offset (AVO) in multi-offset seismic records are strongly affected by relative changes of Poisson's ratio. AVO analysis opens the possibility to distinguish ‘bright spots’ due to gas accumulation from those caused by other changes in lithology AVO analysis is generally carried out with ray tracing and the Zoeppritz equations as tools for forward modeling. Some inversion procedures have been developed to infer changes in the contrast of the elastic parameters. However, it was recognized that the quality of the available modeling and inversion techniques was insufficient. The alternative approach we propose for the modeling is (i) an extension of the reflectivity method to smoothly varying media, and (ii) a cost-efficient linearized finite-difference technique.In our study we have minimized structural difficulties in order to concentrate on a 2D target zone in a quasi-layered background media. Then small changes in elastic parameter contrasts can be estimated by inversion using a linear least-squares approach: the waveform match between the synthetic and the seismic multi-offset gathers is obtained by perturbing the model parameters in the target zone. We have also evaluated the impact of the use of a priori information. Finally a 2D seismic non-linear modeling has been carried out to understand what reservoir-scale information is contained in the seismic reflection data. Participants in this project were AGIP (Italian oil company), the Politecnico di Milano(POLIMI) and the Institut Francais du Petrole (IFP). Each partner of this project has contributed specialskills and experience. The task of AGIP, the industrial partner, was to analyse a real data ase with the maximum depth possible, and to extract all information on the elastic parameters.The role of the academic partner, Politecnico di Milano, was to improve elastic reflectivity modeling and to evaluate the uncertainties of both amplitude-versus-offset (AVO) studies and of linearized elastic inversion that are caused by uncertainties in the model of the overburden and by noise in the data. An effort was also made to implement the inversion technique in the (ω-k domain. The role of IFP was to develop both linearized elastic modeling and inversion techniques using finite differences, and to evaluate the inversion technique on a large-scale synthetic data set. In addition, a multidisciplinary team of IFP has carried out a numerical simulation of synthetic data bas d on controlled earth parameters followed by processing and interpretation. Part I deals with the impact of a priori information on seismic inversion.It was decided to improve the most accurate modeling technique, i.e., the well known reflectivity method, so that it better represents shorter offsets; subsequently it was extended to media that vary continuously with depth, and to media that vary smoothly in lateral direction. This was achieved by the hybridization of ray tracing and reflectivity methods. A powerful (and essentially exact) 3D modeling technique resulted, albeit limited to quasi ID media. The AGIP group was able to analyse a real data case that was suitable for this kind of modeling. This group has carried out a careful and systematic AVO analysis and a comparison between the elastically modeled data and the real data. The processing and interpretation steps are described below. Another important step was to determine error bars in linearized inversion. For this, it was useful to move the problem from the spatial domain to the frequency-wave number domain. This move opened the possibility to bette understand the ‘conditioning‘. The inversion in the ω-k domain (with some preliminary results) is presented below. It was necessary to understand not only linearized inversion, but the limits of AVO in general. To this end a complete study of the interaction between AVO and velocity errors was carried out. This thorough understanding is particularly important if the velocity is not as perfectly known as in the real data case we analysed. Part II describes a 2D linearized elastic inversion technique and its evaluation on synthetic data.A 2D linearized elastic modeling procedure based on the computation of the Jacobian matrix using finite differences was proposed, analysed and implemented. Its accuracy was tested for models containing a few scattering points. Besides linearized modeling, a linearized inversion technique using a least-squares formulation was implemented to find the elastic perturbations in the 2D target zone. The inversion was tested on seismic data generated from scattering points. Next a large-scale synthetic data set generated for a gas-bearing sand model by a full-wave elastic finite-difference code was inverted. We show that, by using a plane stratified reference medium and limited windows for parameters data centered on the reflected P-P waves, one can determine the band-limited perturbations of the P-impedance and - to a lesser degree - the band-limited perturbations of the S-impedance at reasonable effort. In addition we show that the inversion results are closer to the actual perturbations than the results obtained with more conventional seismic processing procedures. Part III describes a numerical simulation of synthetic data for the Mesaverde outcrop.The objective was to understand what geological information is embodied in the seismic data that can be used to delineate and characterize reservoirs. Both geological and elastic models were constructed from the Mesaverde outcrop study and from industrial logs of equivalent formations. Then (marine) synthetic data were generated using a full-wave 2D elastic propagation code. Conventional seismic data processing was applied to obtain a stacked section. This section was calibrated using impedance logs at theoretical well locations (this process corresponds to wavelet-extraction processing). Finally complementary direct and inverse stratigraphie impedance modeling techniques were applied to build the most likely impedance section and to give a geological significance to the impedance variations.

Linearization is a goud approximation if the reference medium is sufficiently close to the actual one. The method we propose deals with a 1D reference medium and has been presented in Mace et al (1992). It is adapted to determine a 2D elastic target zone embedded in an almost laterally invariant elastic background. The method is based on the computation of the Jacobian matrix and uses a conjugate gradient algorithm to solve the optimization problem. In this paper, the linearized inversion method is valuated on synthetic prestack marine data from a gas-bearing sand model.

For each shot s, the linearization consists in substituting the observed field Ps by the sum of the primary field Ps and of the scattered field ðPs where Ps corresponds to the non linear propagation in the reference medium m0 and ðPs is a linear function of the perturbation ðm which is computed from the Jacobian Js of the non linear operator at m0 . The process of linearization is associated with smalt perturbations.

Introduction Les fractures obstetricales sont un evenement rare au decours d’un accouchement, soit par voie basse, soit par cesarienne. Le but de cette etude est de preciser l’epidemiologie, la presentation, les modalites du traitement ainsi que l’evolution des fractures obstetricales. Methodes De 1996 a 2006, une etude retrospective a permis de revoir les dossiers consecutifs des patients pris en charge pour une fracture obstetricale, a l’exception des paralysies isolees du plexus brachial. Resultats Soixante quatre patients ont ete suivis, presentant un total de 70 fractures. Il a ete observe : 22 fractures de la clavicule, 33 fractures des os longs (humerus n = 15, femur n = 17 dont une forme bilaterale, tibia n = 1), 14 fractures decollement epiphysaire (extremite inferieure humerus n = 4, extremite inferieure du femur n = 6, extremite superieure du tibia n = 4) et 1 fracture de plusieurs cotes. Le diagnostic a ete fait a J0 dans 43 % (28/43). Sept lesions nerveuses etaient associees aux fractures (plexus brachial n = 4, paralysie radiale n = 3). On denombre 8 grossesses gemellaires. Seul 58 % des accouchements etaient par voie basse eutocique. Il y a eu 19 cesariennes (en urgence n = 12, programmee n = 7) et 12 voies basses dystociques, dont 5 extractions par forceps. Seuls 5 malades ont necessite un traitement chirurgical avec osteosynthese (fracture-decollement epiphysaire extremite inferieure humerus n = 4, du femur n = 1). Le recul moyen des fractures obstetricales diagnostiquees avant le 01/01/2006 (n = 54) est de 595 jours. Un seul cas de fragilite osseuse constitutionnelle a ete diagnostique au decours. Seuls deux malades ont ete operes a distance de la fracture pour prise en charge de complications. Discussion Les factures obstetricales sont des fractures de bon pronostic. Elles beneficient de l’extraordinaire remodelage osseux de l’enfant en croissance. Le traitement orthopedique initial, le moins agressif possible, donne un bon resultat dans la majorite des cas et les sequelles sont rares. Une osteosynthese est indiquee pour les decollements epiphysaires tres instables. Une surveillance reguliere jusqu’a la fin de la croissance est necessaire. La cesarienne ne met pas a l’abri des fractures obstetricales.

Introduction L’osteo-onychodysplasie est une maladie genetique autosomique dominante, rare, touchant le systeme musculo-squelettique, les ongles, les reins et les yeux. Les anomalies ungueales, cornes iliaques agenesies ou hypoplasies rotuliennes avec luxation de l’appareil extenseur du genou, ainsi que les atteintes du coude sont des signes classiques de la maladie. Materiel et Methode Nous avons revu retrospectivement 26 patients suivis pour une osteo-onychodysplasie, afin de determiner l’influence de la severite de la maladie et du mode de transmission genetique sur les manifestations musculosquelettiques, leur traitement et leur evolution, notamment au niveau de l’appareil extenseur du genou. La severite de la maladie a ete classee selon le score de severite de l’atteinte orthopedique de Farley : 10 legers, 13 moderes, 3 severes. Resultats Nous avons une population avec un rapport fille/garcon de 6/20, l’âge moyen a la premiere consultation etait de 6,1 ans avec un recul moyen de 6 ans. Vingt-quatre patients avaient une atteinte de la rotule bilaterale, 15 etaient symptomatiques de leurs genou. Dix patients avaient une luxation de la tete radiale avec raideur articulaire du coude. Un patient a souffert d’une compression du nerf ulnaire necessitant une neurolyse chirurgicale. Un seul patient a presente une atteinte renale. Treize patients ont ete operes, dont 10 au niveau du genou. Il y a eu 8 operations de reaxation de l’appareil extenseur par une intervention sur les parties molles, dont 2 bilaterales. Deux cas de flessum de genou irreductibles sur contractures ont necessite une osteotomie femorale de deflexion du genou. Deux patients ont ete traites par arthroscopie, un cas pour des corps libres intra-articulaires et l’autre pour une menisectomie. Une patiente a eu une patellectomie. Deux allongements de tendons d’Achille ont ete necessaires pour des pieds equins, et 2 patients ont dus etre operes de deformations severes du pied. Un seul patient a necessite une intervention au niveau du coude. Les patients operes de reaxation d’appareil extenseur du genou n’ont pas presente de recidive de luxation. Conclusion Les manifestations musculosquelettiques de l’osteo-onychodysplasie sont situees en majorite aux genoux et aux coudes. Si la chirurgie est rarement necessaire pour les coudes, les interventions de reaxation de l’appareil extenseur du genou par une intervention sur les parties molles ont montres de bons resultats, independamment de la severite de la maladie ou du mode de transmission.

Introduction La pseudarthrose congenitale de jambe pose un probleme therapeutique complexe dont le but est d’obtenir une consolidation osseuse se maintenant dans le temps. Nous proposons une nouvelle technique basee sur le principe de la membrane induite proposee pour les pseudarthroses septiques de jambe. Materiel et Methode Entre 2003 et 2005, 3 enfants ont ete operes d’une pseudarthrose congenitale de jambe dont 2 entrant dans le cadre d’une neurofibromatose. Il s’agissait de 2 garcons et d’une fille d’un âge moyen au moment de l’intervention d’1 an et 8 mois. La pseudarthrose, de forme atrophique, etait localisee dans 2 cas au tiers inferieur, et dans 1 cas au quart inferieur de jambe. Une excision des zones dystrophiques a ete realisee a la fois sur le tibia et la fibula dans tous les cas. Une entretoise en ciment a ete mis en place dans 3 cas sur le tibia et 1 cas sur la fibula, associee a un enclouage centromedullaire et a une immobilisation plâtree cruro-pedieuse pour 2 mois. Une greffe spongieuse autologue prelevee sur une crete iliaque posterieure a alors ete realisee apres ablation du ciment et completee par une immobilisation cruro-pedieuse pour une duree de 4 mois. Resultats Le recul moyen etait de 2 ans et 5 mois. La consolidation du tibia a ete acquise d’emblee dans tous les cas, en moyenne a 5 mois de l’apport osseux. Dans 2 cas, la consolidation de la fibula a ete acquise dans les memes delais. Une greffe intertibio-fibulaire complementaire a ete realisee dans 1 cas a un an de l’intervention initiale (ciment uniquement sur le tibia) pour une absence de consolidation de la fibula. Le raccourcissement moyen du fragment jambier etait de 3 cm. Discussion De nombreuses techniques chirurgicales ont ete decrites avec un taux de succes variable. La reconstruction par greffon fibulaire vascularise controlateral apres resection des zones dystrophiques et l’utilisation du fixateur externe d’Ilizarov ont donne les meilleurs resultats. Il s’agit de techniques lourdes non denuees de complications en particulier sur la jambe controlaterale. La technique de la membrane induite est une technique en 2 temps simple et seduisante qui permet d’epargner la jambe saine et evite les complications du fixateur externe. Cette technique reste encore a valider par une serie et un recul plus important.

We present a method for solving the linearized seismic acoustic inverse problem. 1D reference medium is sufficiently accurate allow the linearization, the computation can made much less than for non linear inversion use of an especially designed algorithm that 2D If a to be by we present here. A synthetic example illustrates the effectiveness of linearized inversion about a 1D reference medium. Such a method could be of great practical interest for a sharp description of stratigraphic traps in nearly flat areas.

A method and device for improving the restoration of the images obtained from samples taken from acoustic signals received by a lateral aimed sonar provides for the selection of samples from the signals received, the time interval between the samples selected being smaller at the beginning of the echo reception window than at the end thereof so as to improve the power of resolution of the sonar for directions of low obliqueness. The sampling may be carried out at a variable frequency or else at a very high fixed frequency, the selection then being made among all the samples obtained.

System to measure the coefficients of reflection of submerged surfaces such as the seabed, by comparison of the intensities of acoustic impulses propagated between a source and a receptor, both of which are submerged, and that of the echoes of these impulses on the reflectors. For this purpose, there is provided a programmed calculator, an interface card to communicate with different units: an echo-sounder, a source triggering detector, a shot box to control the source and a recorder, a programmable attenuator, an acquisition card driven by the calculator and bearing an adjustable type filter and a circuit, also controlled by the calculator, for modifying the functioning parameters of the attenuation and of the filter, and fixing the starting parameters.