•Evaluation framework for automatic stroke lesion segmentation from MRI•Public multi-center, multi-vendor, multi-protocol databases released•Ongoing fair and automated benchmark with expert created ...ground truth sets•Comparison of 14+7 groups who responded to an open challenge in MICCAI•Segmentation feasible in acute and unsolved in sub-acute cases
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Ischemic stroke is the most common cerebrovascular disease, and its diagnosis, treatment, and study relies on non-invasive imaging. Algorithms for stroke lesion segmentation from magnetic resonance imaging (MRI) volumes are intensely researched, but the reported results are largely incomparable due to different datasets and evaluation schemes. We approached this urgent problem of comparability with the Ischemic Stroke Lesion Segmentation (ISLES) challenge organized in conjunction with the MICCAI 2015 conference. In this paper we propose a common evaluation framework, describe the publicly available datasets, and present the results of the two sub-challenges: Sub-Acute Stroke Lesion Segmentation (SISS) and Stroke Perfusion Estimation (SPES). A total of 16 research groups participated with a wide range of state-of-the-art automatic segmentation algorithms. A thorough analysis of the obtained data enables a critical evaluation of the current state-of-the-art, recommendations for further developments, and the identification of remaining challenges. The segmentation of acute perfusion lesions addressed in SPES was found to be feasible. However, algorithms applied to sub-acute lesion segmentation in SISS still lack accuracy. Overall, no algorithmic characteristic of any method was found to perform superior to the others. Instead, the characteristics of stroke lesion appearances, their evolution, and the observed challenges should be studied in detail. The annotated ISLES image datasets continue to be publicly available through an online evaluation system to serve as an ongoing benchmarking resource (www.isles-challenge.org).
Context. The properties of the smallest subunits of cometary dust contain information on their origin and clues to the formation of planetesimals and planets. Compared to interplanetary dust ...particles or particles collected during the Stardust mission, dust collected in the coma of comet 67P/Churyumov-Gerasimenko (67P) during the Rosetta mission provides a resource of minimally altered material with known origin whose structural properties can be used to further the investigation of the early solar system. Aims. The cometary dust particle morphologies found at comet 67P on the micrometer scale are classified, and their structural analysis is extended to the nanometer scale. Methods. We present a novel method for achieving the highest spatial resolution of imaging obtained with the MIDAS Atomic Force Microscope on board Rosetta. 3D topographic images with resolutions down to 8 nm were analyzed to determine the subunit sizes of particles on the nanometer scale. Results. Three morphological classes can be determined: (i) fragile agglomerate particles of sizes larger than about 10 μm comprised of micrometer-sized subunits that may themselves be aggregates and show a moderate packing density on the surface of the particles. (ii) A fragile agglomerate with a size of about a few tens of micrometers comprised of micrometer-sized subunits that are suggested to be aggregates themselves and are arranged in a structure with a fractal dimension lower than two. (iii) Small micrometer-sized particles comprised of subunits in the size range of hundreds of nanometers that show surface features that are again suggested to represent subunits. Their differential size distributions follow a log-normal distribution with means of about 100 nm and standard deviations between 20 and 35 nm. Conclusions. The properties of the dust particles found by MIDAS represent an extension of the dust results of Rosetta to the micro- and nanometer scale. All micrometer-sized particles are hierarchical dust agglomerates of smaller subunits. The arrangement, appearance, and size distribution of the smallest determined surface features are reminiscent of those found in chondritic porous interplanetary dust particles. They represent the smallest directly detected subunits of comet 67P.
Study objective Out-of-hospital hypotension has been associated with increased mortality in traumatic brain injury. The association of traumatic brain injury mortality with the depth or duration of ...out-of-hospital hypotension is unknown. We evaluated the relationship between the depth and duration of out-of-hospital hypotension and mortality in major traumatic brain injury. Methods We evaluated adults and older children with moderate or severe traumatic brain injury in the preimplementation cohort of Arizona’s statewide Excellence in Prehospital Injury Care study. We used logistic regression to determine the association between the depth-duration dose of hypotension (depth of systolic blood pressure <90 mm Hg integrated over duration minutes of hypotension) and odds of inhospital death, controlling for significant confounders. Results There were 7,521 traumatic brain injury cases included (70.6% male patients; median age 40 years interquartile range 24 to 58). Mortality was 7.8% (95% confidence interval CI 7.2% to 8.5%) among the 6,982 patients without hypotension (systolic blood pressure ≥90 mm Hg) and 33.4% (95% CI 29.4% to 37.6%) among the 539 hypotensive patients (systolic blood pressure <90 mm Hg). Mortality was higher with increased hypotension dose: 0.01 to 14.99 mm Hg-minutes 16.3%; 15 to 49.99 mm Hg-minutes 28.1%; 50 to 141.99 mm Hg-minutes 38.8%; and greater than or equal to 142 mm Hg-minutes 50.4%. Log2 (the logarithm in base 2) of hypotension dose was associated with traumatic brain injury mortality (adjusted odds ratio 1.19 95% CI 1.14 to 1.25 per 2-fold increase of dose). Conclusion In this study, the depth and duration of out-of-hospital hypotension were associated with increased traumatic brain injury mortality. Assessments linking out-of-hospital blood pressure with traumatic brain injury outcomes should consider both depth and duration of hypotension.
ABSTRACT
Explanation of the observed gas activity based on the parameters of the comet’s nucleus is not an obvious matter. Solutions based on certain thermal models can be obtained, but the use of ...arbitrary values for poorly known model parameters is always required. In this work, we carry out a study of the dependence of gas activity on these parameters and assess the importance of each of them. We consider model porous dust layers of diverse structures. Solid state and gas thermal conductivities are examined to estimate the possible range of effective thermal conductivity. The simulation results are embedded in a thermal model, explicitly including a radiative thermal conductivity and a resistance of the dust layer against the gas flow. Sublimation of water ice and supervolatiles (CO2 and CO) is tested at different heliocentric distances. It is shown that when sublimation is the main energy sink, the role of uncertainties in the structure of the layer is small. As the relative contribution of sublimation decreases, the scatter of solutions reaches tens of per cent. The expected large uncertainties in the effective thermal conductivity can also significantly change the gas production. The analysis performed shows that, in spite of the parameter range having been narrowed down by results from the Rosetta mission, the unavoidable uncertainty in the values of some model parameters (e.g. thermal conductivity) blurs the theoretical simulation estimates. Instead of presenting a narrow set of specific solutions, it is desirable to analyse the entire range of possible solutions.
Context. Cometary dust particles are remnants of the primordial accretion of refractory material that occurred during the initial formation stages of the solar system. Understanding their physical ...structure can help constrain their accretion process. Aims. The in situ study of dust particles that were collected at slow speeds by instruments on board the Rosetta space mission, including GIADA, MIDAS, and COSIMA, can be used to infer the physical properties, size distribution, and typologies of the dust. Methods. We have developed a simple numerical simulation of aggregate impact flattening to interpret the properties of particles collected by COSIMA. The aspect ratios of flattened particles from simulations and observations are compared to distinguish between initial families of aggregates that are characterized by different fractal dimensions Df. This dimension can differentiate between certain growth modes: the diffusion limited cluster–cluster aggregates (DLCA, Df ≈ 1.8), diffusion limited particle–cluster aggregates (DLPA, Df ≈ 2.5), reaction limited cluster–cluster aggregates (RLCA, Df ≈ 2.1), and reaction limited particle–cluster aggregates (RLPA, Df ≈ 3.0). Results. The diversity of aspect ratios measured by COSIMA is consistent with either two families of aggregates with different initial Df (a family of compact aggregates with Df close to 2.5–3 and some fluffier aggregates with Df ≈ 2) or aggregates formed by a single type of aggregation process, such as DLPA. In that case, the cohesive strength of the dust particles must span a wide range to explain the range of aspect ratios observed by COSIMA. Furthermore, variations in cohesive strength and velocity may play a role in the detected higher aspect ratio range (>0.3). Conclusions. Our work allows us to explain the particle morphologies observed by COSIMA and those generated by laboratory experiments in a consistent framework. Taking into account all observations from the three dust instruments on board Rosetta, we favor an interpretation of our simulations based on two different families of dust particles with significantly distinct fractal dimensions that are ejected from the cometary nucleus.
ABSTRACT
A hierarchical model of microstructure of cometary dust seems to accurately capture the morphological complexity of these particles as observed by the Rosetta mission to the ...67P/Churyumov–Gerasimenko. The main aim of this work is to investigate how uncertainties in the knowledge of the microstructure of the surface layer affect our estimates of gas production. New models that incorporate scale of inhomogenieties in a sound theoretical framework are used for hierarchical dust layers. The studied layers are constructed in two steps: first we design ballistic aggregates as the building units and then, using these porous blocks, assemble the layers constrained by the known porosity range. The mean pore size and permeability are studied. Modelling is performed for various values of porosity, grain size, and layer thickness. The simulation results are embedded in the thermal model, explicitly including a radiation thermal conductivity and a resistance of the dust layer for the gas flow. It is shown that the average pore size is satisfactorily approximated by a linear function of the ratio of the effective porosity of the layer to the degree of filling. Simple fittings were obtained for the layer permeability. Our results indicate that in the expected range of nucleus porosity, the gas production rate is weakly dependent on the detailed layer microstructure, and appropriate effective values of homogeneous dust layers can be used to evaluate the gas activity. We also note that adding complex elements into the model yields unavoidable statistical uncertainties within several tens of per cent.
Background Early-life human rhinovirus infection has been linked to asthma development in high-risk infants and children. Nevertheless, the role of rhinovirus infection in the initiation of asthma ...remains unclear. Objective We hypothesized that, in contrast to infection of mature BALB/c mice, neonatal infection with rhinovirus promotes an IL-25–driven type 2 response, which causes persistent mucous metaplasia and airways hyperresponsiveness. Methods Six-day-old and 8-week-old BALB/c mice were inoculated with sham HeLa cell lysate or rhinovirus. Airway responses from 1 to 28 days after infection were assessed by using quantitative PCR, ELISA, histology, immunofluorescence microscopy, flow cytometry, and methacholine responsiveness. Selected mice were treated with a neutralizing antibody to IL-25. Results Compared with mature mice, rhinovirus infection in neonatal mice increased lung IL-13 and IL-25 production, whereas IFN-γ, IL-12p40, and TNF-α expression was suppressed. In addition, the population of IL-13–secreting type 2 innate lymphoid cells (ILC2s) was expanded with rhinovirus infection in neonatal but not mature mice. ILC2s were the major cell type secreting IL-13 in neonates. Finally, anti–IL-25 neutralizing antibody attenuated ILC2 expansion, mucous hypersecretion, and airways responsiveness. Conclusions These findings suggest that early-life viral infection could contribute to asthma development by provoking age-dependent, IL-25–driven type 2 immune responses.
Study objective Survival is significantly reduced by either hypotension or hypoxia during the out-of-hospital management of major traumatic brain injury. However, only a handful of small studies have ...investigated the influence of the combination of both hypotension and hypoxia occurring together. In patients with major traumatic brain injury, we evaluate the associations between mortality and out-of-hospital hypotension and hypoxia separately and in combination. Methods All moderate or severe traumatic brain injury cases in the preimplementation cohort of the Excellence in Prehospital Injury Care study (a statewide, before/after, controlled study of the effect of implementing the out-of-hospital traumatic brain injury treatment guidelines) from January 1, 2007, to March 31, 2014, were evaluated (exclusions: <10 years, out-of-hospital oxygen saturation ≤10%, and out-of-hospital systolic blood pressure <40 or >200 mm Hg). The relationship between mortality and hypotension (systolic blood pressure <90 mm Hg) or hypoxia (saturation <90%) was assessed with multivariable logistic regression, controlling for Injury Severity Score, head region severity, injury type (blunt versus penetrating), age, sex, race, ethnicity, payer, interhospital transfer, and trauma center. Results Among the 13,151 patients who met inclusion criteria (median age 45 years; 68.6% men), 11,545 (87.8%) had neither hypotension nor hypoxia, 604 (4.6%) had hypotension only, 790 (6.0%) had hypoxia only, and 212 (1.6%) had both hypotension and hypoxia. Mortality for the 4 study cohorts was 5.6%, 20.7%, 28.1%, and 43.9%, respectively. The crude and adjusted odds ratios for death within the cohorts, using the patients with neither hypotension nor hypoxia as the reference, were 4.4 and 2.5, 6.6 and 3.0, and 13.2 and 6.1, respectively. Evaluation for an interaction between hypotension and hypoxia revealed that the effects were additive on the log odds of death. Conclusion In this statewide analysis of major traumatic brain injury, combined out-of-hospital hypotension and hypoxia were associated with significantly increased mortality. This effect on survival persisted even after controlling for multiple potential confounders. In fact, the adjusted odds of death for patients with both hypotension and hypoxia were more than 2 times greater than for those with either hypotension or hypoxia alone. These findings seem supportive of the emphasis on aggressive prevention and treatment of hypotension and hypoxia reflected in the current emergency medical services traumatic brain injury treatment guidelines but clearly reveal the need for further study to determine their influence on outcome.
Wheat, one of the most important food crops, is threatened by a blast disease pandemic. Here, we show that a clonal lineage of the wheat blast fungus recently spread to Asia and Africa following two ...independent introductions from South America. Through a combination of genome analyses and laboratory experiments, we show that the decade-old blast pandemic lineage can be controlled by the Rmg8 disease resistance gene and is sensitive to strobilurin fungicides. However, we also highlight the potential of the pandemic clone to evolve fungicide-insensitive variants and sexually recombine with African lineages. This underscores the urgent need for genomic surveillance to track and mitigate the spread of wheat blast outside of South America and to guide preemptive wheat breeding for blast resistance.
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