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International audience; A long-range transmission demonstrator for low data rate environmental sensor networks is under development. It uses the ISM free-access frequency band at 433 MHz. In addition to distance attenuation, a major issue is the presence of numerous radio frequency interferences in this band. With a view to optimizing the sensor life and cost, the system complexity has been shifted to the central station which will be based on array processing techniques. In this paper, we describe a spatial cyclostationary detector for triggering the acquisition of sensor data frames in this highly corruptive radio environment.

In humans CT imaging is a validated method for the study of adipose tissue distribution and for quantification of visceral and subcutaneous fat. Equivalent methods adapted to murine models of obesity are still lacking. Indeed most attempts to quantify fat tissues in vivo, using dedicated small animal micro-CT, involve long-term X-ray exposure which limits longitudinal studies. We have overcome this limitation by using a human clinical CT which allows very fast 3D imaging and minimal radiation exposure for the study of adipose tissue distribution in mice in vivo. Moreover, we have developed an automatic image analysis method for the segmentation of Hounsfield units of adipose tissues and for the localization of abdominal regions of interest.

International audience; In this communication, we expose the classical steps used in medical imaging to reconstruct dynamical organs such as the human heart. We indicate the limitations still encountered nowadays, and propose some potential perspective to improve the segmentation and reconstruction of the cardiac surfaces as a function of time.

International audience; Bioluminescence imaging is a recent modality to visualize biological effects more especially for small animals. However the acquired images are degraded by diffusion and absorption phenomena from the tissue and by the acquisition system itself. In this paper, we use restoration methods to enhance the quality of bioluminescence images. We propose a model for image formation and an experimental determination of the PSF (Point Spread Function). Several methods of restoration are compared on test images generated according to the model and on real data. This comparison is insured by using MSE (Mean Square Error) and two quantitative criteria. Results establish that the statistical methods give more accurate restoration and well adapted for Bioluminescence Imaging.

International audience; Image registration is a valuable technique for medical diagnosis and treatment. In this paper, we present an enhanced implementation of the popular iterative closest point (ICP) algorithm developed for the registration of 3D free-form closed surfaces. The main step of the ICP consists of finding the closest points between data sets which are then used to estimate the parameters of the global rigid transformation. We propose a new technique based on the use of a look up matrix for finding the best correspondence pairs. The algorithm, called Comprehensive ICP (CICP) algorithm, is then successfully applied for the registration of 3D data of the left ventricle of the heart, acquired using two different medical imaging modalities.

International audience; In this paper, a new local quasi-interpolant is constructed for fitting a 3D data defined on the sphere-like surface S. After mapping the surface S onto a rectangular domain, we use the tensor product of cubic polynomial B-splines and recently developed 2¼-periodic uniform algebraic trigonometric B-splines (UAT B-splines) to introduce a new expression of the associated quasi-interpolant Q. The use of UAT B-splines is necessary to enforce some boundary conditions which are useful to ensure the C1 continuity of the associated surface. The new method has been successfully applied to reconstruct human organs such as lung and left ventricle of the heart.

International audience; In the transgenic research era, the understanding of the functional consequences of the genes deletions or mutations in order to investigate the origin of human transgenic disease, requires the development of non invasive study methods on murine models. Our aim is to develop new Down syndrome models and a 3D reconstruction software using MEMRI at 9.4T. To improve contrast and spatial resolution at high magnetic field, the Mn2+ contrast agent shows powerful paramagnetic properties leading to a significant increase of MRI signal [1]. Mn2+ is a unique marker for neuroarchitecture, neuronal connections and functions therefore particularly interesting for neuropathological studies in vivo. In order to investigate the morphological and structural consequences on the central nervous system development in new mice models of human chromosome 21 aneuploïdies, we used MEMRI and. we also developed a powerful tool in order to perform an automatic segmentation and 3D reconstruction of three brain structures.

International audience; In this paper, we propose a modified variational splines fitting (MVSF) algorithm for the reconstruction and comparison of medical surfaces. The MVSF algorithm presents the advantage to use high precise and low complex approximation of the equations of energy in the discrete temporal domain, compared to previously presented methods. It also takes into account the periodicity constraints encountered when reconstructing sphere-like shape closed surfaces. Moreover, it gives straightly the mean square error (MSE) between the original data and the reconstructed data, which is useful to quantify the approximation introduced by the reconstruction. The developed model has been successfully applied for real biomedical data; in particular for the reconstruction and comparison of the left ventricle of human heart, acquired by SPECT and ultrasound imaging modalities.

International audience; In digital image processing, skeletonization is a valuable technique for the characterization of complex 3D porous media, such as bone, stone and soils. 3D thinning algorithms are usually used to extract one-voxel wide skeleton from 3D porous objects while preserving the topological information. Models based on simplified skeletons have been shown to be efficient in retrieving morphological information from large scale disordered objects at a local level. In this paper, we present a series of 3D skeleton-based image processing techniques for evaluating the micro-architecture of large scale disordered porous media. The proposed hybrid skeleton method combines curve and surface thinning methods with the help of an enhanced shape classification algorithm. Results on two different porous objects demonstrate the ability of the hybrid skeleton method to provide significant topological and morphological information.

International audience; In this paper, a semi automatic active contour method based on Chan-Vese model is proposed for the segmentation of mouse brain MR images. First, a 2 ½ D strategy is applied on the axial images to segment the 3D volume of interest. The method takes into account the special shape of the object to segment. Moreover, the user defines the limits where to search these contours and also provides an initial contour. This semi automatic method makes that human intervention is limited and the tedious manual handling is greatly reduced. Results have shown that the brain volumes estimated by the method are identical to expert manually estimated volumes. Last but not least, the new method was used in the analysis of the cerebral malformations linked to Trisomy 21: no significant difference of the brain volumes between Tri-somy 21 mice and the control ones were found.

International audience; The segmentation of different cerebral structures of mice is becoming more and more important due to the growing interest in finding small animal models of human diseases. In this work, variational atlases are constructed by manual segmentation of various MRI brain images of reference and trisomy 21 mice. These atlases are then registered to assist the segmentation of fine cerebral structures such as the cerebellum and the hippocampus. A modified Chan-Vese segmentation method is used for the detection of these structures. Global as well as local comparison of the reconstructed surfaces and volumes are hence conducted to better understand the gene involved in the morphological malformations associated to trisomy.

International audience; Research on bone and teeth mineralization in animal models is critical for understanding human pathologies. Genetically modified mice represent highly valuable models for the study of osteo/dentinogenesis defects and osteoporosis. Current investigations on mice dental and skeletal phenotype use destructive and time consuming methods such as histology and scanning microscopy. Micro-CT imaging is quicker and provides high resolution qualitative phenotypic description. However reliable quantification of mineralization processes in mouse bone and teeth are still lacking. We have established novel CT imaging-based software for accurate qualitative and quantitative analysis of mouse mandibular bone and molars. Data were obtained from mandibles of mice lacking the Fibromodulin gene which is involved in mineralization processes. Mandibles were imaged with a micro-CT originally devoted to industrial applications (Viscom, X8060 NDT). 3D advanced visualization was performed using the VoxBox software (UsefulProgress) with ray casting algorithms. Comparison between control and defective mice mandibles was made by applying the same transfer function for each 3D data, thus allowing to detect shape, colour and density discrepencies. The 2D images of transverse slices of mandible and teeth were similar and even more accurate than those obtained with scanning electron microscopy. Image processing of the molars allowed the 3D reconstruction of the pulp chamber, providing a unique tool for the quantitative evaluation of dentinogenesis. This new method is highly powerful for the study of oro-facial mineralizations defects in mice models, complementary and even competitive to current histological and scanning microscopy appoaches.

International audience; In obese humans CT imaging is a validated method for follow up studies of adipose tissue distribution and quantification of visceral and subcutaneous fat. Equivalent methods in murine models of obesity are still lacking. Current small animal micro-CT involves long-term X-ray exposure precluding longitudinal studies. We have overcome this limitation by using a human medical CT which allows very fast 3D imaging (2 sec) and minimal radiation exposure. This work presents novel methods fitted to in vivo investigations of mice model of obesity, allowing (i) automated detection of adipose tissue in abdominal regions of interest, (ii) quantification of visceral and subcutaneous fat. For each mouse, 1000 slices (100μm thickness, 160 μm resolution) were acquired in 2 sec using a Toshiba medical CT (135 kV, 400mAs). A Gaussian mixture model of the Hounsfield curve of 2D slices was computed with the Expectation Maximization algorithm. Identification of each Gaussian part allowed the automatic classification of adipose tissue voxels. The abdominal region of interest (umbilical) was automatically detected as the slice showing the highest ratio of the Gaussian proportion between adipose and lean tissues. Segmentation of visceral and subcutaneous fat compartments was achieved with 2D ½ level set methods. Our results show that the application of human clinical CT to mice is a promising approach for the study of obesity, allowing valuable comparison between species using the same imaging materials and software analysis

International audience; Image registration is a valuable technique for medical diagnosis and treatment. In this paper, we present an enhanced implementation of the popular iterative closest point (ICP) algorithm developed for the registration of 3D free-form closed surfaces, based on the use of a look up matrix for finding the best correspondence pairs. The algorithm, called Comprehensive ICP (CICP) algorithm, is then successfully applied for comparing two sequences of 3D surfaces of the left ventricle of the heart, obtained from two different modalities: 4D Echography and Gated SPECT. The results show a good correspondence between the reconstructed sequence from 4D Echography and the reference Gated SPECT sequence. This study can be extended to comparing different medical reconstructions of sphere-like shaped organs collected from different modalities.

International audience; In any cable or power line communications, impulse noise is known to be the most difficult noise to filter. In particular, non periodic asynchronous impulse noise is impossible to predict. Under such noise conditions, the OFDM1 symbol generally used in PLC2 is corrupted. To overcome this problem, the signal-to-noise ratio is generally improved by detecting and/or filtering the noise. This leads however to heavy detection and computing time in comparison with the disturbance duration. In this paper, we study the parameters of the noise generated by a load commutation and propose a new approach that consists in controlling the commutation instant of the load. This approach reduces by up to 15 dB the asynchronous impulsive noise emitted by a resistive load in a 40.96-μs typical Homeplug AV3 OFDM symbol duration. Synchronisation is integrated in electronic commutation system. Results show that the load value does not influence the magnitude of the impulse noise.

International audience; The iterative closest point (ICP) algorithm is an efficient algorithm for robust rigid registration of 3D data. Results provided by the algorithm are highly dependent upon the step of finding corresponding pairs between the two sets of 3D data before registration. In this paper, a look up matrix is introduced in the point matching step to enhance the overall ICP performance. Convergence properties and robustness are evaluated in the presence of Gaussian and impulsive noise, and under different data set sizes. The new algorithm has been evaluated on 3D medical data. It has been applied successfully to register closed surfaces acquired using different medical imaging modalities.

International audience; Facing the disaffection of students for electronic engineering studies, we decided to have global brainstorming with students and then with teachers and enterprises to define new engineering courses that could be attractive and useful. The paper describes the problematic addressed, the way we used to build this curriculum and the new course as proposed to the students. We also emphasize all along the text on the problems we had to solve till the attribution of the accreditation.