Modélisation des flux cérébraux par une analogie électrique : validation par vélocimétrie IRM

The cine Phase-Contrast Magnetic Resonance (PCMR) sequence is the only noninvasive technique for the study of cerebrospinal fluid (CSF) oscillations. It can provide CSF and blood flow measurements throughout the cardiac cycle. To study cerebral hydro-hemodynamic, models have been developed; nevertheless the majority of these models did not take into account the CSF oscillations. The objective of this study was to establish reference values for cerebral hydro-hemodynamic and propose a new electrical model of the brain dynamics.Material and methodsCSF and blood flows were measured in 19 control subjects by PCMR imaging. Dynamic flow images were analyzed on dedicated software to reconstruct the flow curves during the cardiac cycle. An electrical analogue was realized. The inputs of the model were fed by PCMR arterial and venous flows to simulate CSF oscillations. The simulated CSF oscillations were compared to the measured CSF oscillations to validate the model.ResultsThe key parameters of the CSF and blood flow curves were obtained, e.g. total cerebral blood flow was 688 ± 115 mL/min, ventricular CSF oscillatory volume was 0.05 ± 0.02 mL/cardiac cycle, and the subarachnoid CSF oscillatory volume was 0.55 ± 0.15 mL/cardiac cycle. A close agreement was found between measured and simulated cerebral CSF oscillations.ConclusionThis study established the main values characterizing cerebral hydrodynamics in a control population. It provided a better understanding of the mechanisms of intracranial volumes regulation during the cardiac cycle. Our results are now used in clinical practice and the model proposed is effective to study cerebral hydro-hemodynamic.     

Une syringocèle révélée par un abcès périntéal

Purpose

The authors present a clinical report of a perforate syringocele diagnosed in a male patient and they review the clinical, radiological and therapeutic aspects of this disease.

Case report

A 50-year-old man attended the emergency room with perineal abscess. Computerized Tomography (CT) scan was used to establish the diagnosis. This patient also underwent urethrocystoscopy, sonography and retrograde urethrography.

Results

Treatment consisted of open surgical evacuation of the perineal abscess with bladder catheter. Urethrocystoscopy showed a large perforate syringocele in the urethra with no need for endoscopy marsupialization. No recurrence was observed at follow-up at 3 months.

Conclusion

Syringocele is a rare malformation which usually is asymptomatic. It can be congenital or acquired and can be classified into four morphological types. The most frequent treatment is endoscopic marsupialization of the syringocèle. Open surgical excision is recommended for complicated syringocèle with abscess or perineal pain.     

Classification des stades de sommeil par des réseaux de neurones artificiels hiérarchiques

The goal of our work is to provide an automatic analysis and decision tool for sleep stages classification based on an artificial neural networks (ANN). The first difficulty lies in choosing the physiological signals representation and in particular the electroencephalogram (EEG). Once the representation adopted, the next step is to design the optimal neural network determined by a learning and validation process of data from a set of sleep records. We studied several configurations of conventional ANN giving results varying from 62 to 71 %, then we proposed a new hierarchical configuration, which gives a rate of 74 % correct classification for six stages. These results lead us to further explore this issue at the representation and design of ANNs to improve the performance of our tool.     

Innovations technologiques récentes en détection pour la Tomographie par Emission de Positons

Since the recognition of the clinical value of Positron Emission Tomography (PET) for the diagnosis and staging of several cancers, the PET systems have evolved to systems associating PET and Computed Tomography (CT). The main constraint for clinical imaging is to reduce the acquisition duration. As a consequence, PET detectors are faster and emit more light than the BGO crystal used previously. These detectors allow an improvement of the count rate performance of the PET systems, reducing the scattered and the random events while increasing the true events at high activity concentration. Among the new crystals, some allow measuring the time of flight of the annihilation photons. This measurement further improves the performance of the systems. The spatial resolution of clinical PET systems is still equal to 5 mm at best. High spatial resolution PET systems dedicated to small animal imaging have been developed. These systems use similar crystal materials as the clinical systems. However, in order to permit spatial resolution close to 1 mm, the crystal elements have much smaller transverse dimensions than that of clinical systems. The detectors are compact using position sensitive photomultipliers or photodiodes. In order to preserve the uniformity of the spatial resolution over the transverse field of view of the tomographs, solutions allowing the measurement of the depth of interaction of the photons in the crystal have been designed. New compact detectors based on semi conductors are currently investigated.     

Liste inédite des Reptiles et Amphibiens récoltés par Alcide dˈOrbigny en Amérique méridionale

The complete list of Reptiles and Amphibians collected by dˈOrbigny in South America (Uruguay, Argentina, Chile, Bolivia) is published for the first time. The list consists of six species of Chelonians, 26 of Saurians, 22 of Ophidians and 16 of Amphibians (one Gymnophiona and 15 Anura). In this list, 31 species were new and are still valid. The plates were published separately and prior to the publication of the ‘Reptiles’ chapter in the Voyage dans lˈAmérique méridionale, and sometimes before the corresponding volume of the Erpétologie générale of Duméril and Bibron 〚3〛. The publication dates of the plates change the known name, author(s) and dates of the several figured species.     

L’élastographie par ultrasons ou résonance magnétique : de nouveaux outils de diagnostic en cancérologie

Despite recent progress, breast cancer remains today a major public health problem as it represents the main morbidity incidence for woman with 42,000 new cases and 11,600 deaths per year in France. X-Ray mammography which is the “gold standard” exam for breast screening relies on an excellent sensitivity (nevertheless its quality is varying with respect to breast density). However, its specificity for malignancy diagnosis remains moderate leading to many useless interventions for lesions proven a posteriori to be benign by histology. The other imaging techniques such as echography and magnetic resonance imaging (MRI) also possess their own limits. Echography is strongly operator-dependent. Dynamic MRI with injection of contrast agents has a high sensitivity for breast cancer detection (>90%) but suffers from a moderate specificity (50 to 80% according to the type of cancer). In parallel, although it is strongly subjective, the act of palpation remains today a major act in the workflow of breast screening. Since Egyptian ancient ages, the physicians practise the act of palpating body parts in order to determine tissues stiffness and a hardly deformed mass within an organ is often related to the presence of an abnormal lesion. Palpation is not only useful for screening and diagnosis as the surgeon also uses it during interventions to be effectively guided towards the pathological area. Recently, new techniques based on ultrasound or magnetic resonance imaging finally made it possible to map organs elasticity in a quantitative way. These “elastography” techniques could play soon an important role in medical imaging.     

Transmission héréditaire de l’information épigénétique par le gamète mâle

What determines phenotype is one of the most fundamental questions in biology. Historically, most studies have focused on genetics but more recent studies have revealed the existence of epigenetic modifications that are not based on DNA sequencing but are essential for appropriate gene expression. Importantly, these epigenetic modifications can be inherited by the offspring. Thus, both male and female gametes contain inherited epigenetic information.     

Effets de la fluorescence résiduelle dans les tissus biologiques sur les signaux de fluorescence résolus temporellement par la méthode des éléments finis

A computational model based on finite element method is derived to examine how the simulated time-dependent signals are related to the presence of residual fluorescence in biological media surrounding a fluorescent object. We apply a subtraction technique on recorded data when imperfect uptake of fluorescing agent into the tumor is considered. We show the limits of the subtracting method for low target: background fluorescent absorption contrast by extracting the time to reach the half maximum and analyzing the maximum of the time-resolved signals versus target depth.     

Cancer et Hérédité

Sans résumé     

Effets de l’âge et du genre sur la perfusion cérébrale régionale étudiée par deux méthodes d’analyse statistique voxel-par-voxel

Fully automated analysis programs have been applied more and more to aid for the reading of regional cerebral blood flow SPECT study. They are increasingly based on the comparison of the patient study with a normal database. In this study, we evaluate the ability of Three-Dimensional Stereotactic Surface Projection (3D-SSP) to isolate effects of age and gender in a previously studied normal population. The results were also compared with those obtained using Statistical Parametric Mapping (SPM99).MethodsEighty-nine ^99mTc-ECD-SPECT studies performed in carefully screened healthy volunteers (46 females, 43 males; age 20–81 years) were analysed using 3D-SSP. A multivariate analysis based on the general linear model was performed with regions as intrasubject factor, gender as intersubject factor and age as covariate.ResultsBoth age and gender had a significant interaction effect with regional tracer uptake. An age-related decline (p < 0.001) was found in the anterior cingulate gyrus, left frontal association cortex and left insula. Bilateral occipital association and left primary visual cortical uptake showed a significant relative increase with age (p < 0.001). Concerning the gender effect, women showed higher uptake (p < 0.01) in the parietal and right sensorimotor cortices. An age by gender interaction (p < 0.01) was only found in the left medial frontal cortex. The results were consistent with those obtained with SPM99.Conclusion3D-SSP analysis of normal rCBF variability is consistent with the literature and other automated voxel-based techniques, which highlight the effects of both age and gender.     

Stéréosélectivité de la réduction de la 3′, 5′-di-O-benzoyl-2′-bromo-2′-désoxyuridine par l'hydrure de tributylétain

Samples of sodium alginate from Laminaria digitata were oxidised in aqueous solution to different extents by the addition of calculated amounts of sodium metaperiodate. An empirical measure of the molecular stiffness of the products, both before and after reduction with sodium borohydride, was obtained by studying the sensitivity of their intrinsic viscosities to changes in the ionic strength of the solution. The results showed that, whereas the stiffness decreased very sharply with increasing degree of oxidation, it changed very little upon subsequent reduction of the products. From this, and the known structures of the inter-residue hemiacetals in the unreduced products, it was inferred that the increase in flexibility brought about by oxidation is specifically associated with rotation about the three bonds adjoining C-4, C-5, the original ring-oxygen atom, and C-1 of the oxidised hexuronic-acid residues. This rotation was considerably less-hindered than the rotation around the glycosidic linkage in both the intact alginate and in the partially oxidised and reduced products. The conversion of only a small percentage of the stiff pyranoid rings into these centres of high, local flexibility had a marked effect on the overall flexibility of the chains, showing that the possible presence of such centres should be taken into account in any discussion of the solution properties of heteropolysaccharides or of polysaccharides that may have suffered slight chemical modification.     

Effets produits chez trois espèces de criquets par l'ingestion d'hydrocarbures polyaromatiques réputés cancérogènes

In a first approach to studying the effects of air pollutants, we describe some experimental results obtained after ingestion of polyaromatic hydrocarbons (HAP)^* by three species of locusts (Gomphocerus sibiricus, Gomphocerus rufus and Euchorthippus pulvinatus). We wanted to evaluate their toxicity, then to locate them in the organism. Two HAP, carcinogenic for mammals, were used. They are highly toxic for our locusts. Ingestion of 0.015 or 0.06 mg of 3 methylcholanthrene kills respectively 25 % and 50 % of them. Moreover, benzo-a-pyrene seems to have a greater toxicity, and E. pulvinatus is the most resistant species. Strongly fluorescent in UV light, 3 MC and BaP can be easily detected in the organism after dissection, and with more detail using frozen material. The microscope shows absorption activity of midgut; most of the organs are consequently invaded by intact hydrocarbon or its various derivatives. Muscles and reproductive organs show a bright fluorescence, which reaches its maximum in the nervous system. Tubes of Malpighi seem to be the principal route of elimination of these products. The remarkable susceptibility of some organs is encouraging for the progress of our study.