Scintigraphie de perfusion cérébrale positionnelle : résultats physiologiques et applications cliniques

To assess the impact of standing on brain perfusion, 125 brain perfusion scans in the upright and supine position were performed, including 108 patients. Perfusion values were compared using a relative quantitative approach and a segmentation of vascular territories with the help of an atlas of brain perfusion. We found a change in the distribution of the perfusion in favor of the vertebro-basilar system in the upright position. We discuss the case of a patient whose symptoms could be explained with the help of the comparison of brain perfusion scans in the upright and supine position. Atheromatous and post-dissection stenosis and their influence on perfusion are also discussed.     

Le sujet cérébral: une esquisse historique et conceptuelle

Since the middle of the 20th century, numerous discourses and practices, both within and outside scientific and philosophical disciplines, have manifested the development of the notion of the human being as acerebral subject. The brain appears to be the only organ of the body that we need, and that has to be exclusively ours, in order for each individual to be himself or herself. Sincepersonhood is the quality or condition of being an individual person,brainhood is thus the quality or condition of being a brain. This property defines the cerebral subject. The anthropology ofbrainhood may seem a natural consequence of progress in the neurosciences. However, it is rooted in 17th-century developments in the philosophies of matter and personal identity. The neurosciences confirm and reinforce this perspective. The author outlines the historical narrative concerning the development of the cerebral subject as well as some contemporary issues arising from the neurosciences.     

Le diagnostic et le suivi thérapeutique des tumeurs cérébrales intra-parenchymateuses par l’imagerie par résonance magnétique multimodale

The multimodal magnetic resonance imaging (MMRI) has an important role in cancer care. This non-invasive and non-ionizing technique provides vital information for the diagnosis and answers to various questions of clinicians before, during and after treatment. The MMRI can specify the localization expanding process; it allows establishing the differential diagnosis of a brain tumor and a circumscribed lesion of another type, to approach the diagnosis of the tumor lesion nature as well as establishing the histological grade of glial tumor in view of lesion monitoring after treatment. The multimodal magnetic resonance imaging has a major contribution to the management progress of the brain tumors. Thus, this paper reviews the value of these MRI modalities in the diagnosis, management and therapy of brain tumors.     

Cinétiques de la fixation du 18F-FDG dans les structures cérébrales : faisabilité et résultats préliminaires

ObjectDynamic positron emission tomography (dyn-PET) acquisitions using the radiotracer ¹⁸F-deoxyglucose (¹⁸F-FDG) are mainly developed in research studies of brain PET in kinetic modelling to determine the local glucose consumption rate. This procedure is difficult to establish, due to its requirement for blood sampling. Here, we propose a simple approach to constructing time–activity curves (TACs) for four different brain structures (the arterial & venous regions and grey & white matter) based on direct image measurements on chronologically reconstructed image volumes of regions of interest.Materials and methodsWe applied our processing on 14 control subjects to extract their physiological state. We defined the reference ¹⁸F-FDG kinetic curves as a “population averaged TAC” for four structures. To increase the curves accuracy, our method included the evaluation of two normalization based on the integral of the activity curve in the arteries and the veins.ResultsThe method showed discrimination between artery, venous, grey and white matters. The two normalization methods significantly reduce the dispersion for the grey and white matter curves and that venous normalization showed the best overall efficiency.ConclusionWe have designed and evaluated an approach for directly defining PopAv_TACs which are representative of given anatomical structures.     

Scintigraphie cérébrale de perfusion et troubles cognitifs d’origine vasculaire

The vascular cognitive impairment (VCI) is a heterogeneous group of various etiologies, which share a presumed vascular cause. Although the age is the most important risk factor, the cardiovascular risk factors are also involved. A relatively high proportion of these cognitive disorders could be prevented or delayed. Only the treatment of arterial hypertension is recognized as a factor in preventing vascular dementia. MRI is the examination of choice for the investigation of cerebral vascular pathology. However, this morphological imaging is insufficient and does not provide useful functional information. Perfusion brain SPECT is not widely used in the exploration of VCI. Strategies for screening VCI are not standardized and long-term studies are needed to establish the better prevention of cognitive vascular disorders. This article aims to summarize the possible benefit of cerebral perfusion SPECT in the exploration of VCI.     

Cancer et Hérédité

Sans résumé     

Les remplissages sédimentaires des coquilles de céphalopodes triasiques. Mécanismes et intérêt paléoécologique

Experiments have been carried out in laboratory onplastic cephalopod models in order to study most aspects of sedimentary shell filling of Ceratites and Nautilus from the German Upper Muschelkalk. In most cases the shells had a horizontal position when being filled by the sediment. The exception of filling in upright position has been observed mainly for Ceratites nodosus nodosus (Bruguière, 1792), Acanthoceratites spinosus (Philippi, 1901) except the species A. spinosus penndorfi (Rothe, 1955), Acanthoceratites evolutus (Philippi, 1901) and the nautilus Germanonautilus bidorsatus (Schlotheim, 1804); it is due to the width of their shells. In no case the sediment filling of cephalopod shells gives information about the depth of the depositional environment. On the other hand it is a good indicator of the waving occurring on the sea floor and the reworking of the sediment.     

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.     

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.