Intracranial Stents Being Modeled as a Porous Medium: Flow Simulation in Stented Cerebral Aneurysms

Intracranial aneurysms may be treated by flow diverters, alternatively to stents and coils combination. Numerical simulation allows the assessment of the complex nature of aneurismal flow. Endovascular devices present a rather dense and fine strut network, increasing the complexity of the meshing. We propose an alternative strategy, which is based on the modeling of the device as a porous medium. Two patient-specific aneurysm data sets were reconstructed using conventional clinical setups. The aneurysms selection was done so that intra-aneurismal flow was shear driven in one and inertia driven in the other. Stents and their porous medium analog were positioned at the aneurysm neck. Physiological flow and standard boundary conditions were applied. The comparison between both approaches was done by analyzing the velocity, vorticity, and shear rate magnitudes inside the aneurysm as well as the wall shear stress (WSS) at the aneurysm surface. Simulations without device were also computed. The average flow reduction reaches 76 and 41% for the shear and inertia driven flow models, respectively. When comparing the two approaches, results show a remarkable similarity in the flow patterns and magnitude. WSS, iso-velocity surfaces and velocity on a trans-sectional plane are in fairly good agreement. The root mean squared error on the investigated parameters reaches 20% for aneurysm velocity, 30.6% for aneurysm shear rate, and 47.4% for aneurysm vorticity. It reaches 20.6% for WSS computed on the aneurysm surface. The advantages of this approach reside in its facility to implement and in the gain in computational time. Results predicted by the porous medium approach compare well with the real stent geometry model and allow predicting the main effects of the device on intra-aneurismal flow, facilitating thus the analysi

Double-lumen balloon microcatheter-assisted occlusion of cerebral vessels with coils: a technical note

The purpose of this study was to describe a balloon-assisted double-lumen microcatheter technique to perform a controlled and tight coil packing of a vascular segment for vessel occlusion. This technique can be performed immediately after a test occlusion with the balloon kept in place and was, as illustrated in six cases, in our experience safe, straight forward to use and fas

Intracranial Stents Being Modeled as a Porous Medium: Flow Simulation in Stented Cerebral Aneurysms

Intracranial aneurysms may be treated by flow diverters, alternatively to stents and coils combination. Numerical simulation allows the assessment of the complex nature of aneurismal flow. Endovascular devices present a rather dense and fine strut network, increasing the complexity of the meshing. We propose an alternative strategy, which is based on the modeling of the device as a porous medium. Two patient-specific aneurysm data sets were reconstructed using conventional clinical setups. The aneurysms selection was done so that intra-aneurismal flow was shear driven in one and inertia driven in the other. Stents and their porous medium analog were positioned at the aneurysm neck. Physiological flow and standard boundary conditions were applied. The comparison between both approaches was done by analyzing the velocity, vorticity, and shear rate magnitudes inside the aneurysm as well as the wall shear stress (WSS) at the aneurysm surface. Simulations without device were also computed. The average flow reduction reaches 76 and 41% for the shear and inertia driven flow models, respectively. When comparing the two approaches, results show a remarkable similarity in the flow patterns and magnitude. WSS, iso-velocity surfaces and velocity on a trans-sectional plane are in fairly good agreement. The root mean squared error on the investigated parameters reaches 20% for aneurysm velocity, 30.6% for aneurysm shear rate, and 47.4% for aneurysm vorticity. It reaches 20.6% for WSS computed on the aneurysm surface. The advantages of this approach reside in its facility to implement and in the gain in computational time. Results predicted by the porous medium approach compare well with the real stent geometry model and allow predicting the main effects of the device on intra-aneurismal flow, facilitating thus the analysis

Screening of DUB activity and specificity by MALDI-TOF mass spectrometry

Deubiquitylases (DUBs) are key regulators of the ubiquitin system which cleave ubiquitin moieties from proteins and polyubiquitin chains. Several DUBs have been implicated in various diseases and are attractive drug targets. We have developed a sensitive and fast assay to quantify in vitro DUB enzyme activity using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Unlike other current assays, this method uses unmodified substrates, such as diubiquitin topoisomers. By analyzing 42 human DUBs against all diubiquitin topoisomers we provide an extensive characterization of DUB activity and specificity. Our results confirm the high specificity of many members of the OTU and JAMM DUB families and highlight that all USPs tested display low linkage selectivity. We also demonstrate that this assay can be deployed to assess the potency and specificity of DUB inhibitors by profiling 11 compounds against a panel of 32 DUBs

Not all cows are epidemiologically equal:quantifying the risks of bovine viral diarrhoea virus (BVDV) transmission through cattle movements

International audienceMany economically important cattle diseases spread between herds through livestock movements. Traditionally, most transmission models have assumed that all purchased cattle carry the same risk of generating outbreaks in the destination herd. Using data on bovine viral diarrhoea virus (BVDV) in Scotland as a case example, this study provides empirical and theoretical evidence that the risk of disease transmission varies substantially based on the animal and herd demographic characteristics at the time of purchase. Multivariable logistic regression analysis revealed that purchasing pregnant heifers and open cows sold with a calf at foot were associated with an increased risk of beef herds being seropositive for BVDV. Based on the results from a dynamic within-herd simulation model, these findings may be partly explained by the age-related probability of animals being persistently infected with BVDV as well as the herd demographic structure at the time of animal introductions. There was also evidence that an epidemiologically important network statistic, "betweenness centrality" (a measure frequently associated with the potential for herds to acquire and transmit disease), was significantly higher for herds that supplied these particular types of replacement beef cattle. The trends for dairy herds were not as clear, although there was some evidence that open heifers and open lactating cows were associated with an increased risk of BVDV. Overall, these findings have important implications for developing simulation models that more accurately reflect the industry-level transmission dynamics of infectious cattle diseases

Progressive melorheostosis in the peripheral and axial skeleton with associated vascular malformations: imaging findings over three decades

A 28-year old woman presented with Leri's disease (melorheostosis) and the rare combination of complex vascular malformations and lymphatic anomalies. Multifocal melorheostosis was segmental and unilateral, located in the left axial and peripheral skeleton, fifth thoracic vertebral body, fifth rib. left upper limb and lumbosacral spine (third lumbar body to first sacral segment). Sacral involvement was associated with spinal canal stenosis. Additionally the patient had multiple nevi and had suffered from left hemiplegia since birth. Lymphangiectasia of the mesentery and thorax led to chylothorax resistant to therapy for which the patient underwent a pleuropericardiectomy. Death ensued due to respiratory failur