Fuzzy Fibers: Uncertainty in dMRI Tractography

Fiber tracking based on diffusion weighted Magnetic Resonance Imaging (dMRI) allows for noninvasive reconstruction of fiber bundles in the human brain. In this chapter, we discuss sources of error and uncertainty in this technique, and review strategies that afford a more reliable interpretation of the results. This includes methods for computing and rendering probabilistic tractograms, which estimate precision in the face of measurement noise and artifacts. However, we also address aspects that have received less attention so far, such as model selection, partial voluming, and the impact of parameters, both in preprocessing and in fiber tracking itself. We conclude by giving impulses for future research

DeepTract: A Probabilistic Deep Learning Framework for White Matter Fiber Tractography

We present DeepTract, a deep-learning framework for estimating white matter fibers orientation and streamline tractography. We adopt a data-driven approach for fiber reconstruction from diffusion weighted images (DWI), which does not assume a specific diffusion model. We use a recurrent neural network for mapping sequences of DWI values into probabilistic fiber orientation distributions. Based on these estimations, our model facilitates both deterministic and probabilistic streamline tractography. We quantitatively evaluate our method using the Tractometer tool, demonstrating competitive performance with state-of-the art classical and machine learning based tractography algorithms. We further present qualitative results of bundle-specific probabilistic tractography obtained using our method. The code is publicly available at: https://github.com/itaybenou/DeepTract.git

Sticky bubbles

We discuss the physical forces that are required to remove an air bubble immersed in a liquid from a corner. This is relevant for inkjet printing technology, as the presence of air bubbles in the channels of a printhead perturbs the jetting of droplets. A simple strategy to remove the bubble is to ush the ink past the bubble by providing a high pressure pulse. In this report we rst compute the viscous drag forces that such a ow exerts on the bubble. Then, we compare this to the \sticking forces" on the bubble, due to the capillary interaction with the wall. From this we can estimate the required ow velocities for bubble removal, as a function of channel geometry, contact angle and ink properties. Finally, we investigate other ways to exert a force on a trapped bubble. In particular we focus on forces induced by electric elds which can alter the contact angle of the drop, or by locally applying thermal gradients. Once again, these forces are compared to the sticking forces to identify the parameters where the bubble can be removed

The cholesterol derivative 27-hydroxycholesterol reduces steatohepatitis in mice.

<p>BACKGROUND & AIMS: Non-alcoholic steatohepatitis is characterized by hepatic steatosis with inflammation. Although steatosis is benign and reversible, inflammation can increase liver damage. Hepatic inflammation has been associated with accumulation of cholesterol in lysosomes of Kupffer cells. 27-Hydroxycholesterol (27HC), a derivative of cholesterol formed by CYP27A1, can mobilize cholesterol from the lysosomes to the cytoplasm. We investigated whether 27HC can change the intracellular distribution cholesterol and reduce hepatic inflammation in mice. METHODS: We transplanted bone marrow from irradiated wild-type or Cyp27a1(-/-) mice to mice that do not express the low density lipoprotein receptor (Ldlr(-/-)), which are hyperlipidemic; 9 weeks later, mice were fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 3 months. In a separate experiment, Ldlr(-/-) mice were given subcutaneous injections of 27HC and placed on regular chow or HFC diets for 3 weeks. Blood and liver tissues samples were collected and analyzed for intracellular cholesterol distribution and inflammation. RESULTS: In Ldlr(-/-) mice that received bone marrow transplants from Cyp27a1(-/-) mice, lysosomes of Kupfer cells had a greater accumulation of cholesterol than those of mice that received bone marrow from wild-type mice, after the HFC diet. Liver histology and gene expression analyses showed increased inflammation and liver damage in mice given bone marrow transplants from Cyp27a1(-/-) mice and placed on the HFC diet. Administration of 27HC to Ldlr(-/-) mice, following the HFC diet, reduced the accumulation of lysosomal cholesterol and hepatic inflammation, compared with mice that were not given 27HC. CONCLUSIONS: Accumulation of cholesterol in lysosomes of Kupfer cells promotes hepatic inflammation in mice. The cholesterol derivative 27HC reduces accumulation of cholesterol in lysosomes and might be used to treat non-alcoholic steatohepatitis.</p>

Mesures visant à freiner la hausse des coûts dans l’assurance obligatoire des soins : rapport du groupe d'experts

La santé est un des ingrédients fondamentaux du bien-être humain. On peut escompter que l’élévation du niveau de vie, la multiplication des maladies chroniques et le risque croissant de multimorbidité dû à l’évolution démographique entraînent une hausse des coûts de la santé imputable à plusieurs facteurs. Au total, ces coûts sont passés de 37,5 milliards de francs en 1996 à 77,8 milliards en 2015, tandis que ceux de l'AOS ont grimpé de 10,8 à 27,5 milliards de francs. Notons qu'au cours de cette période en question, l’importance économique a augmenté non seulement en termes absolus mais également rapporté au produit intérieur brut (PIB), indice qui mesure la performance économique d’un pays. Alors que les coûts globaux de la santé représentaient, en 1996, 9,2 % du PIB par année, ce pourcentage était supérieur à 12 en 2015. En comparaison avec la croissance démographique, les coûts des soins de santé ont également augmenté de façon disproportionnée: la progression des prestations nettes dans l’AOS est en effet de 4 % environ par assuré en moyenne, soit 3,5 % déduction faite de l’inflation. Certes, les bases de données ne sont pas parfaites, mais le faisceau d’indices pointant une tendance à l’accélération de la hausse des coûts est incontestable. Pour tenter de la freiner, une intervention politique s’impose de plus en plus, si bien que les mesures de nature à permettre au système de santé de rester financièrement viable sur la durée, tant pour les payeurs de primes que les pouvoirs publics, gagnent en importance. Les mesures envisagées dans le présent rapport visent en particulier à éviter que des prestations médicales inutiles et évitables soient fournies et, partant, à contribuer à freiner la hausse des coûts. (Contexte