Quantitative geometric analysis of rib, costal cartilage and sternum from childhood to teenagehood

Better understanding of the effects of growth on children’s bones and cartilage is necessary for clinical and biomechanical purposes. The aim of this study is to define the 3D geometry of children’s rib cages: including sternum, ribs and costal cartilage. Three-dimensional reconstructions of 960 ribs, 518 costal cartilages and 113 sternebrae were performed on thoracic CT-scans of 48 children, aged four months to 15 years. The geometry of the sternum was detailed and nine parameters were used to describe the ribs and rib cages. A "costal index" was defined as the ratio between cartilage length and whole rib length to evaluate the cartilage ratio for each rib level. For all children, the costal index decreased from rib level one to three and increased from level three to seven. For all levels, the cartilage accounted for 45 to 60% of the rib length, and was longer for the first years of life. The mean costal index decreased by 21% for subjects over three years old compared to those under three (p<10-4). The volume of the sternebrae was found to be highly age dependent. Such data could be useful to define the standard geometry of the paediatric thorax and help to detect clinical abnormalities.Grant from the ANR (SECUR_ENFANT 06_0385) and supported by the GDR 2610 “Biomécanique des chocs” (CNRS/INRETS/GIE PSA Renault

Nonlinear inversion of multifrequency GPR data in tomographic configurations

The accurate tomographic reconstruction of structures starting from Ground Penetrating Radar (GPR) data is useful in many real-world scenarios, ranging from the characterization of buried regions to the inspection of tree trunks. Unfortunately, the practical application of advanced inverse-scattering methods requires an accurate modeling of the GPR system, and in particular of the antenna and antenna-medium interactions [1]. In this work, the combination of an advanced antenna modelling technique with a nonlinear multifrequency inversion method is investigated from an experimental point of view. The GPR measurements, acquired with a lightweight radar system prototype in different configurations, are processed with a hybrid reconstruction approach that aims at combining the benefits of qualitative processing and quantitative inversion techniques [2]. The reconstruction of cylindrical targets buried in a sand box and in free space are considered, evaluating the influence of the antenna and its modelling on the inversion. Results are promising and allow to draw indications about the applicability of the proposed method to GPR configurations. [1] A. De Coster and S. Lambot, “Full-wave removal of internal antenna effects and antenna-medium interactions for improved ground-penetrating radar imaging,” IEEE Transactions on Geoscience and Remote Sensing, 2019. [2] F. Boero et al., “Microwave tomography for the inspection of wood materials: imaging system and experimental results,” IEEE Transactions on Microwave Theory and Techniques, vol. 66, no. 7, pp. 3497–3510, Jul. 2018

Short-Term Scientific Missions on electromagnetic modelling and inversion techniques for Ground Penetrating Radar-COST Action TU1208

This work aims at offering an overview on the scientific results stemming from a selection of Short-Term Scientific Missions (STSMs) funded by the COST (European COoperation in Science and Technology) Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar" and dealing with the development of electromagnetic modelling and inversion techniques for Ground Penetrating Radar applications. STSMs are important means to develop linkages and scientific collaborations between participating institutions involved in a COST Action. Scientists have the possibility to go to an institution abroad, in order to undertake joint research and share experience, techniques, equipment and infrastructures that may not be available in their own institution

Evaluating Ground-Penetrating Radar use for water infiltration monitoring

International audienceGround-Penetrating Radar (GPR) was tested to monitor water infiltration in sand. Water was injected down an 81 cm long tubed hole, with a piezometer recording the depth of water and a tap valve used to adjust it to 15 cm ± 2 cm above the bottom of the tube. During the 20 minutes of infiltration a GPR system recorded a trace every second with its transmitter and receiver antennae at a fixed offset position on the surface. The signal, enhanced by differential correction, allows for tracing the evolution of top and bottom limits of the water bulb in space and time. Comparison with hydrodynamic model of the infiltration process and simulated radargrams prove that the GPR reflections trace the wetting front and the saturation bulb. A quantified estimation of the evolution of the top border of the wetting zone is provided

Advanced ground-penetrating radar for soil moisture retrieval. In: Multiscale Hydrologic Remote Sensing: Perspectives and Applications

peer reviewedChang N.-B., Hong Y

Peat soil thickness and carbon storage in the Belgian High Fens: insights from multi-sensor UAV remote sensing

editorial reviewedPeatlands are known to store a large amount of carbon, but global warming and associated changes in hydrology have the potential to accelerate peatland carbon emissions. An in-depth understanding of carbon dynamics within these peatlands is therefore important. However, peatlands are complex ecosystems, and acquiring accurate and reliable estimates of how much carbon is stored underneath the Earth&#8217;s surface is inherently challenging even at small scales. Here, Unmanned Aerial Vehicles (UAVs) equipped with RGB, multispectral, thermal infrared, and LiDAR sensors were combined with Ground Penetrating Radar (GPR) technology and traditional field surveys, to provide a comprehensive 4D monitoring of a peatland landscape in the Belgian High Fens. Data was collected along a hillslope-floodplain transition. We aimed to establish links between the above- and below-ground factors that control soil carbon status, identify the key drivers of carbon storage as well as explore the potential of UAV remote sensing for spatial mapping of peat depth and carbon stock. Our results indicated that peat thickness widely varied (0.2 to 2.1 m) at small scales and is negatively correlated with elevation (r= -0.39, p<0.001). We found that soil organic carbon (SOC) stock is spatially organized, as abundant carbon was observed at the summit and shoulder of the hill, with an average storage of 670.93 &#177; 108.86 t/ha and 601.47 &#177; 133.40 t/ha, respectively. Moreover, the carbon storage exhibited heterogeneity under different vegetation types, with trees having the highest mean SOC stocks at 722.21 &#177; 37.92 t/ha. Through multiple linear regression, we identified 6 environmental variables that can explain 71.44% of SOC stock variance. Clay content is the most critical factor, accounting for nearly 40% of the variance, followed by topography. Contributions from land surface temperature and vegetation remain below 10%. In addition, UAV data provided accurate estimations of both peat depth and SOC stock, with RMSE and R2 values of 0.13 m and 0.88 for the peat depth test dataset, and 114.42 t/ha and 0.84 for the SOC stock. Our study bridged the gap between surface observations and the hidden carbon reservoir below, this not only allows us to improve our ability to assess the spatial distribution of C stocks but also contributes to our understanding of the drivers of C turnover in these highly heterogeneous landscapes, providing insights for environmental science and climate projections

Hydrogeophysical characterization of soil using ground penetrating radar

The knowledge of the dynamics of soil water is essential in agricultural, hydrological and environmental engineering as it controls plant growth, key hydrological processes, and the contamination of surface and subsurface water. Nearby remote sensing can be used for characterizing non-destructively the hydrogeophysical properties of the subsurface. In that respect, ground penetrating radar (GPR) constitutes a promising high resolution characterization tool. However, notwithstanding considerable research has been devoted to GPR, its use for assessing quantitatively the subsurface properties is constrained by the lack of appropriate GPR systems and signal analysis methods. In this study, a new integrated approach is developed to identify from GPR measurements the soil water content and hydraulic properties governing water transfer in the subsurface. It is based on hydrodynamic and electromagnetic inverse modeling. Research on GPR has focused on GPR design, forward modeling of GPR signal, and electromagnetic inversion to estimate simultaneously the depth dependent dielectric constant and electric conductivity of the shallow subsurface, which are correlated to water content and water quality. The method relies on an ultrawide band stepped frequency continuous wave radar combined with an off-ground monostatic TEM horn antenna. This radar configuration offers possibilities for real time mapping and allows for a more realistic forward modeling of the radar-antenna-subsurface system. Forward modeling is based on the exact solution of Maxwell's equations for a stratified medium. The forward model consists in elementary linear components which are linked in series and parallel. The GPR approach is validated for simple laboratory and outdoor conditions. GPR signal inversion enables the monitoring of the soil water dynamics, which can be subsequently inverted for estimating the soil hydraulic properties. A specifically designed hydrodynamic inverse modeling procedure which requires only water content data as input is further developed and validated to obtain the soil hydraulic properties under laboratory conditions.(AGRO 3)--UCL, 200