Réseaux de neurones et électroencéphalogramme : fructueuse associationNeural networks and electroencephalogram: fruitful association

For the last two decades, neural networks have been progressively used in the field of biomedical research. Among them, electroencephalography largely benefited from these tools. In this paper, we are presenting the main characteristics of neural networks. Those networks are tools which are nicely suitable to the electroencephalogram processing. A large bibliography provides the reader a broad view of the works performed in this field and can be used to begin new studies.     

Hémodialyse : actualités et perspectives

Les systèmes d'épuration extrarénale présentent avec les reins naturels l'analogie de réaliser l'épu-ration du plasma à travers une membrane dialysante. Le terme général d'hémodialyse, désigne les systèmes faisant appel à une circulation extracorporelle du sang. Cet article expose les principes généraux du traitement de I'insuffisance rénale chronique terminale par hemodialyse, en insistant plus particulìerement sur des notions d'actualité ou encore en cours de développement. En hémodialyse conventionnelle l epuration des déchets est obtenue principalement par diffusion à travers la membrane dialysante, contrastant ainsi avec le phénomène de filtration observé dans les glomérules des reins naturels. Cependant il existe d'autres modes d'hémodialyse, regroupés sous la dénomination de techniques convectives où l'épuration est obtenue uniquement ou au moins en partie non négligeable par filtration à travers la membrane. Les techniques classiques d'hémodialyse, utilisent des liquides de dialyse et de réinjection dont la composition électrolytique est voisine de celle du plasma. Des techniques plus réntes font appel à des liquides de dialyse de composition électrolytique très diffénte et qui sont donc à l'origine d'un déséquilibre ionique important dans le dialyseur. Ce déséquilibre doit être corrigé par la réinjection d'une solution de composition appropriée.     

Segmentation de la fosse postérieure en IRM fœtale : application biométrique

Posterior fossa segmentation in fetal MR imaging: biometrical application.In order to complete ultrasound scanning and histological tests, magnetic resonance imaging is now considered for the study of prenatal development and fetal pathologies. Due to the recent implementation the quantitative data are still lacking, particularly concerning the central nervous system. Our study is dealing with fetal cerebral MR imaging, and, more precisely, with the biometrical analysis of the different structures of the posterior fossa. Its malformations and pathologies are often due to a trouble of “container-content” and could require a medical termination of pregnancy. So, the need of quantitative information about the relative growth of the different parts of the posterior fossa during the pregnancy is real. We have therefore developped a segmentation method based on region growing with pixel agregation, which has been tested on 67 sagital cross-section MR images. The good segmentation has permitted us to determine the regions of interest (posterior fossa, vermis, brain stem) and to calculate four relative surface measures between them. After technical and clinical validations, the analysis of our results shows that the relative development of these structures is constant and independent of the pregnancy term. It may thus be possible to find standard index for characterizing their relative growth.     

Lutter contre la contamination au bloc opératoireThe battle against contamination in the operating room

A fundamental element of safety and quality of care improvement policy in hospitals is the battle against nosocomial infections. Infections in the OR remain a frequent post-surgery complication factor: their rate, measured in studies, varies between 2 and 5%. The associated rate of lethality of these infections is around 2%, but some post surgery rates can go up to 30%. Some of these infections may have devastating functional consequences. They result in an average increase of the length of stay, from 7–10 days, to up to 20–30 days for important infections. This study proposes a method of evaluation and determination of the contamination risks in the OR, in order to lay down the necessary means to protect patients from post operatory infections. It is a matrix-based method that takes into account two groups of risk factors, each classified according to its risk level. The combination by multiplication of these two factors determines a resulting risk level that allows the adaptation of the necessary means to its prevention. This method is particularly adapted to the definition of the possible interventions amid OR sectors. It also allows to put together the operatory program in the same zone. The different OR components environment will eventually be defined according to each own zone risk factors.     

Estimation du champ de déplacement dense sur une séquence échocardiographique

Dense motion field estimation on a echocardiographic sequence.The estimation of the dense motion field is a first stage treatment often encountered in echocardiographic sequence diagnosis systems. Due to the low time sampling rate and the significant noise of such images, the usual methods based on the first order approximation of the optical flow constraint are inefficient. In this paper we propose a new method capable of dealing with these two problems by using the discrete form of this constraint. However, with this approach we are confronted with a non-convex minimization problem, dealt with by means of a continuation process. Finally, we present the results obtained on different echocardiographic sequences.     

Méthodes de calibrage d''un système électromagnétique pour l''étude et l''évaluation de mesure posturaleCalibration methods of an electromagnetical system for the study and the evaluation of the postural measurement

It is fundamental to model the mechanisms that take place in the human postural system. This permits to interpret and to quantify the phenomenon's that are linked to the postural system. These patterns can be applied in fields such as the diagnosis-help (to detect vertigo, balance disorder), the choice of the therapy, or of re-education. Considering the man as an articulated robot, we could envisage the study of the postural control system with a multi-segment analysis. The mechanism we estimate uses some magnetical 3D trackers that permit to follow the motions, relative to diverse segments, in 3D. The main segments are composed by the head, the neck, the trunk and the limbs. The 3D trackers' response is most of the time riddled with mistakes, notably due to the magnetical field distortion. After showing this distortion, we will see how to correct it, and in which extent the use of this system seems to be well adapted to the study of the postural control system in clinic.     

Étude rhéo-acoustique de la rupture d''agrégates de particules en suspension dans un champ de cisaillement Application à la désagrégation des globules rouges

Rheo-acoustic study of particle aggregate break-up in a shear flow. Application to red blood cell aggregates.Shear-induced disruption of reversible flocs in a concentrated suspension is investigated by ultrasound backscattering in the low shear regime. Fractal flocs are considered as non-Brownian scatterers much smaller than the wavelength, with acoustic properties close to those of the surrounding medium, so that the attenuation of the coherent field is weak and multiple scattering can be neglected. The concept of variance in local particle volume fraction is used to deduce a first order expression of the ultrasound scattering coefficient (cross-section per unit volume) for Rayleigh scatterers in a dense suspension. On the basis of a scaling law for the shear-induced disruption of aggregates, the shear stress dependence of the ultrasonic scattered intensity from a dense suspension of flocs is derived. In a second part, the shear break-up of hardened red blood cell aggregates is investigated in a plane—plane flow geometry by ultrasound scattering. Rheo-acoustical experiments are analysed within the framework of the self consistent field approximation and the scaling laws currently used in microrheological models. Finally, the ability of ultrasonic, light reflectometry and viscometry methods to provide quantitative information about red blood cell aggregation and membrane adhesiveness is discussed.     

Contrôle de qualité en IRM : motivations, méthodes et pratiquesMRI quality assessment motivations methods and practice

The possible motivations of quality assessment of MR scanners are exposed : comparison or reception of MR equipments, follow-up of technical performances, comparative study of image sequences… The technical parameters concerning the image quality are listed, as well as the measurement techniques of these parameters and their influence on the diagnostic capabilities of the scanner. Examples of protocols and of phantoms are described. An overview of the legal regulations concerning the quality assessment puts in prospect the future obligations.     

Optimisation en radiothérapie conformationnelle à l''aide d''un collimateur micro-multilameConformal radiotherapy optimization with a micro-multileaf collimator

Conformal radiotherapy consists in irradiating the target volume while avoiding as far as possible the healthy peripheral tissues and organs at risk. One technique used to treat intracranial tumors consists in using micro-multileaf collimators (MMLC). Given the dose constraints involved, it is of interest to optimize MMLC irradiation parameters. MMLC protocols are optimized in two stages. The orientation of the fields, delimited by a Beam's Eye View technique, is determined using a genetic algorithm method. Weighting of the fields and subfields in intensity modulation and the position of the leaves are optimized for a simulated annealing method. We evaluate the results obtained by the use of the quality indexes defined by the Radiation Therapy Oncology Group. This study demonstrates the advantages of using intensity modulation with the improvement obtained for the indexes. In conformal radiotherapy with MMLC, intensity modulation makes it possible to reduce the number of fields used. It is especially useful to optimize orientations in the case of complex shape target volumes or when there are volumes at risk in the vicinity of the target. If used correctly, MMLC can be a valuable alternative to conventiodiosurgery techniques.     

Évaluation externe de la qualitéQuality control.

Since ten years, the immunohaematology working group of the French Society of Blood Transfusion has organized a quality control. Tests concern essentially the screening and identification of irregular antibodies, direct antiglobulin tests and elutions.     

Organisation, caractérisation et analyse multidimensionnelle des données de la marche: aspects méthodologiquesOrganisation, characterisation and multidimensional analysis ofgait data: methodological aspects

This first article states the problem of the biomechanical data multivariate analysis of the gait. The data base is organised according to a parallelepiped PO where the three directions indicate the subject, the examination number and the trial number. Each non empty cell of PO contains the signals, as angles, moments or EGM activities, recorded during the corresponding empirical situation. Aiming at analysing globally these data, the signals are characterized through average membership values to space-time windows. These values are organised according a data table where the rows correspond to the triplet (cell of PO, time window, limb), and the columns to the space windows of the time variables. The table is investigated through the multiple correspondence analysis (MCA) which yields the more discriminant variables, their relationships and the intra and interindividual differences. The MCA potentialities vs. those of the principal component analysis (PCA) are shown using a didactic example based on simulated data. A second article will illustrate our approach on gait data.     

Modélisations des écoulements pulsés à deux phases, en conduites déformables ou rigidesPulsating flow of two phases in deformable or rigide tubes

A numerical solution of pulsatile flow of two-phases non Newtonian fluid — Newtonian fluid through three different tubes (rigid, elastic, viscoelastic) is presented. The type of this flow exists in blood microcirculation. The iterative process with an implicit difference method is used to solve the both local and integral systems, and to determine the axial velocity profiles, the pressure, the flow rate and the radius distributions at all sections and at every moment.     

Aide à la décision de segmentation d'image par la théorie de Dempster-Shafer : application à une séquence d'images IRM

Le travail présenté clans cet article s'inscrit clans le cadre d'une collaboration avec le service radiologie de I'institut Calot de Berck sur Mer et Siemens. II vise à fournir une aide aux médecins pour le suivi des maladies de la colonne vertébrale. L'objectif est de reconstruire chaque vertébre du rachis lombaire à partir d'une série de coupes parallèles. À partir d'une segmentation initiale, on recherche une segmentation qui représente au mieux le contour anatomique de la vertébre, afin de donner aux médecins une proposition des points faisant réellement partie de la vèrtébre. La méthodologie est basée sur l'utilisation de la théorie de l'évidence pour fusionner les informations. Elle a l'avantage d'introduire la notion de doute entre les différents éléments étudiés. De plus, elle représente mieux la certitude sur la solution de segmentation calculée, et d'autre part elle permet de fusionner des données très hétérogènes. Nous présentons des résultats obtenus à la fois sur des données synthétiques et réelles en précisant les limitations de notre démarche. Nous terminons sur les perspectives à apporter, afin de rendre plus souple la modélisation de fusion employée. aide a la decision I segmentation l fusion de donnees 1 theorie de Dempster-Shafer 1 sequence d'images IRM     

Comparaison de deux techniques de monitorage du débit cardiaque : méthode du contour de pouls et thermodilution artérielle pulmonaire continueComparison of two methods of cardiac output monitoring : systemic arterial pressure and thermodilution curves

Two devices for continuous cardiac output (CO) monitoring at patient bedside were evaluated. Vigilance™ monitor (Baxter Lab.) provides CO measurements by intermittent bolus (TDCO Vig) and continuous thermodilution (CCO Vig) methods, curves are both collected using a pulmonary artery catheter ; PICCO™ monitor (Pulsion Lab.) also provides continuous CO by pulse contour analysis (CCO Pic) and intermittent trans-thoracic thermodilution CO measurements (TDCO Pic), which is used to calculate a calibration factor for further beat-to-beat estimations of CCO Pic. Both systemic arterial pressure and thermodilution curves are collected using a femoral arterial catheter. The objectives of the study were : 1) to compare both methods, 2) to identify the situations possibly responsible for a poor reliability of the pulse contour method. CO measurements (n=301) were recorded simultaneously with both devices in 10 ICU patients : 44 conflicting data pairs, measured after vaso-active drugs initiation or following a calibration procedure performed during cardiac arythmia, were excluded. 257 data pairs for continuous CO measurements were compared using linear regressions and Bland-Altman plots method. Mean values for CCO Vig and CCO Pic were 7,3±2,63 and 7,8±3,04 l.min⁻¹ respectively, and the correlation was significant (r=0,94, p<10⁻⁴). The average difference (bias) was 0,5± 1,06 l.min⁻¹, i.e 7 % overestimation of CO by CCO Pic, and the 95 % confidence interval was large. For 9 among 10 patients the correlation between CCO Vig and CCO Pic was good (Spearman test). For CO values less than 8 l.min⁻¹, the bias and 95 % confidence interval were smaller (0,2±0,66 l.min⁻¹, n=180). Moreover, 108 data pairs for intermittent CO measurements were collected. The correlation between TDCO Vig (7,4±2,7 l.min⁻¹) and TDCO Pic (8,1±1,06 l.min⁻¹) was significant (r=0,97, p<10⁻⁴). The bias was 0,76±0,86 l.min⁻¹ and could be related to a thermal loss between pulmonary and femoral arterial collection. On the whole, the agrement between both continuous CO measurments is acceptable. Since TDCO Pic is used for CCO Pic calibration, the difference between the two CO continuous methods could be partly explained by an overestimation of TDCO Pic. Consequently, the software calibration process should be refined. Moreover, we identified two situations that are responsible for erroneous values of CCO Pic and require a new calibration : cardiac arythmia during PICCO™ calibration, vaso-active drugs initiation.     

Processus de mise en conformité de l''arrêté de périnatalité du 25 avril 2000

Application guide to neonatology regulations.Pregnancy safety, delivery, and care of the mother and baby have been a great concern lately, and these issues have mobilized health professionals. Regulations, means and obligation of results require an organization and a way of working adapted to neonatology. The adoption of the regulation of 25 April 2000, at the Regional Teaching Hospital of Lille, France, has been jointly implemented in three other hospital complexes of different size and with different structures and means. This global approach led to the elaboration of a common guide of neonatology, including steps and actions to be taken in order to meet the requirements. Besides audit, physical inventory, purchases according to the new rule of public market, quality control and maintenance, this study puts the patient at the centre of the collaboration between the medical services, paramedical, industrials and biomedical engineers. Apart from means to mobilize, this close collaboration should rely on the experience of all the participants in order to optimise the conception and maintenance prevention of medical instruments.     

Achats et qualité : évaluation, sélection et maîtrise des sous-contractants

L'évaluation des fournisseurs est l'une des exigences de la norme ISO 9002, formulée au chapitre 4.6 Achats . Les enjeux d'une telle demarche sont de taille, puisqu'elle doit permettre à terme de sélectionner les meilleures offres, aussi bien lors d'achats sur simple facture que lors d'achats par procédure de marché public. Les démarches d'assurance qualité aujourd'hui engagées dans un certain nombre de services biomédicaux concernent essentiellement l'activité de maintenance, et les procédures d'évaluation des fournisseurs mises en œuvre sont relatives aux achats associés à cette activité (pièces détachées, interventions, etc.). II est cependant possible d'élargir ces méthodes à l'ensemble des achats réalisés par le service biomédical (c'est-à-dire également aux achats d'équipements neufs, d'accessoires, de consommables, etc.), de manière à optimiser l'impact des outils mis en place. Cet élargissement peut, en outre, constituer une base de démarche qualité visant l'ensemble de l'organisation associée à l'activité Achat du service biomédical.     

Élaboration d''une politique nationale de maintenance des dispositifs médicaux. L''exemple du Bénin

National regulation medical device maintenance. The Benin example.The development of a country is measured by the good health of its populations. To achieve this goal, the Republic of Benin has built a network of hospitals equipped with medical devices to meet the demand in health care for the public. But one of the obstacles is to keep them under operation because of the absence of a national policy for maintenance. Approaches of solutions are proposed through the development of a national policy for maintenance. That policy will be implemented over the period 2002 to 2006. The question of the management of equipment grants is tackled and it shows the possibility for the broad outline of the charter of gifts. The concern is to control the cost of maintenance and to propose a logical step for the implementation of this policy.     

Spectral data de‐noising using semi‐classical signal analysis: application to localized MRS

In this paper, we propose a new post‐processing technique called semi‐classical signal analysis (SCSA) for MRS data de‐noising. Similar to Fourier transformation, SCSA decomposes the input real positive MR spectrum into a set of linear combinations of squared eigenfunctions equivalently represented by localized functions with shape derived from the potential function of the Schrödinger operator. In this manner, the MRS spectral peaks represented as a sum of these ‘shaped like’ functions are efficiently separated from noise and accurately analyzed. The performance of the method is tested by analyzing simulated and real MRS data. The results obtained demonstrate that the SCSA method is highly efficient in localized MRS data de‐noising and allows for an accurate data quantification.     

Suivi des volumes hydriques pendant la dialyse par bio-impédance multifréquencielle et mesure en continu de l'hématocrite

Le suivi des transferts hydriques pendant la dialyse peut permettre d'améliorer la tolérance du patient au traitement et aider le néphrologue dans sa determination du poids sec. Nous proposons d'effectuer ce suivi par des mesures de bio-impédance corporelle et d'hématocrite dans la ligne artérielle, par méthode optique. La variation de volume extracellulaire est déterminée à partir de la résistance extracellulaire, et celle du volume intracellulaire est déduite de la différence entre la variation du volume ultrafiltré et du volume extracellulaire. La variation du volume plasmatique est calculée d'après la variation de l'hématocrite en s'appuyant sur le principe de conservation des hématies. Des mesures effectuées sur sept patients lors de 21 séances ont monté que les volumes extracellulaires obtenus par bio-impédance sont comparables à ceux calculés à partir des corélations de Watson. Nous avons pu estimer la contribution de chaque compartiment (intracellulaire, interstitiel et plasmatique) au volume ultrafiltré et constater la spécificié de chaque patient. Nous avons obtenu une contribution du compartiment intracellulaire relativement importante chez les patients diabétiques. Un changement du taux d'ultrafiltration en cours de séance se reflète sur la variation du volume extracellulaire.