Optimization of RecoBundles for recognition of short white matter bundles

International audienceShort-range connections have been less studied than long-range connectionq, with most of the white matter fibers atlases available containing mainly large connections. Among the short-range connections atlas, two developed by [6] managed to extract more than 400 bundles for one altas ( ARCHI database [8] ) and more than 600 bundles ( HCP database [1] ). However, they have not been used for white matter segmentation because most techniques for white matter segmentation are optimized for long range connections. Here, we optimize the technique implemented in [2] by analysing the atlas via six geometrical parameters and using bundle specific parameters to increase the quality and the number connections extracted

Retrieving permittivity model parameters for polar liquids and multilayer systems through THz-TDS time-trace data analysis

International audienceWe present new features of the Fit@TDS software for the analysis of polar liquids and multilayer systems. We also show that the modeling of the absorption coefficient of polar liquids can be improved around 2 THz. Hence, this software will enable us to retrieve the parameters of the models depicting polar liquids. It will help to analyze and compare charges motions, playing an important role in biology and chemistry with such effects as protein solvation. Finally, the implementation of a scattering model will improve the accuracy of the results

GeoLab: Geometry-based Tractography Parcellation of Superficial White Matter

Superficial white matter (SWM) has been less studied than long-range connections despite being of interest to clinical research, andfew tractography parcellation methods have been adapted to SWM. Here, we propose an efficient geometry-based parcellation method (GeoLab) that allows high-performance segmentation of hundreds of short white matter bundles from a subject. This method has been designed for the SWM atlas of EBRAINS European infrastructure, which is composed of 657 bundles. The atlas projection relies on the precomputed statistics of six bundle-specific geometrical properties of atlas streamlines. In the spirit of RecoBundles, a global and local streamline-based registration (SBR) is used to align the subject to the atlas space. Then, the streamlines are labeled taking into account the six geometrical parameters describing the similarity to the streamlines in the model bundle. Compared to other state-of-the-art methods, GeoLab allows the extraction of more bundles with a higher number of streamlines

Terahertz time domain spectroscopy data processing: analysing uncertainties to push boundaries: [invited]

International audienceTerahertz spectroscopy provides information on the motion of the charges in a sample at a picosecond scale. To recover this information from Terahertz time-domain spectroscopy (THz-TDS), one usually extracts the experimental refractive index then fits these curves. This approach suffers from several limitations, among them the difficulty to compare models of motions, provide the error bar associated with the extracted magnitude and a resolution limitation coming from the Fourier criteria of the fast Fourier transform. By adopting a Bayesian framework taking into account the experimental uncertainties and directly fitting the time-domain trace, we overcame these limitations. When correlated and epistemic uncertainties/noise are present, the algorithm considers its distribution as part of the data to fit and can mistake it for real physical features. Hence, it offers poor discrimination between good models and bad ones. After a thorough analysis of the experimental noise, we developed a preprocessing software removing epistemic noise on the time traces and providing an estimate of the noise correlation matrix (generalization of the standard deviation). It allows the proper weighting of the error function of the fit using these uncertainties and therefore the derivation of the Akaike information criteria, a metric enabling to calculate the most probable model from a set of models one wants to compare. In addition, by being in the time domain we avoid the Fourier criteria for the resolution and thus could get information on experimental lines down to 30 MHz with a commercial THz-TDS system

Browsing Multiple Subjects When the Atlas Adaptation Cannot Be Achieved via a Warping Strategy

International audienceBrowsing Structural Atlas deep nuclei, functional activations, or other kinds of cortical parcellations. Multimodal, multi-individual, or inter-species display is supported, and adaptations to large scale screen walls have been developed. These very original features make it a unique viewer for structural atlas browsing