Brain MRI lesion load quantification in multiple sclerosis: a comparison between automated multispectral and semi-automated thresholding computer-assisted techniques

Brain magnetic resonance imaging (MRI) lesion volume measurement is an advantageous tool for assessing disease burden in multiple sclerosis (MS). We have evaluated two computer-assisted techniques: MSA multispectral automatic technique that is based on bayesian classification of brain tissue and NIH image analysis technique that is based on local (lesion by lesion) thresholding, to establish reliability and repeatability values for each technique. Brain MRIs were obtained for 30 clinically definite relapsing-remitting MS patients using a 2.0 Tesla MR scanner with contiguous, 3 mm thick axial, T1, T2 and PD weighted modalities. Digital (Dicom 3) images were analyzed independently by three observers; each analyzed the images twice, using the two different techniques (Total 360 analyses). Accuracy of lesion load measurements using phantom images of known volumes showed significantly better results for the MSA multispectral technique (p < 0.001). The mean intra-and inter-observer variances were, respectively, 0.04 ± 0.4 (range 0.04–0.13), and 0.09 ± 0.6 (range 0.01–0.26) for the multispectral MSA analysis technique, 0.24 ± 2.27 (range 0.23–0.72) and 0.33 ± 3.8 (range 0.47–1.36) for the NIH threshold technique. These data show that the MSA multispectral technique is significantly more accurate in lesion volume measurements, with better results of within and between observers’ assessments, and the lesion load measurements are not influenced by increased disease burden. Measurements by the MSA multispectral technique were also faster and decreased analysis time by 43%. The MSA multispectral technique is a promising tool for evaluating MS patients. Non-biased recognition and delineation algorithms enable high accuracy, low intra-and inter-observer variances and fast assessment of MS related lesion load.     

Topologie Des (M - 2)-Courbes Reelles Symetriques

Let X be a non-singular real algebraic curve in CP² of evendegree. In this paper a refinement is proved of a theorem ofKharlamov about (M – 2)-curves that are invariants underthe projective involution. In particular, if the (M –2)-symmetric curve X satisfies the Arnold congruence, then eitherX or its twin is a separating curve. 2000 Mathematics SubjectClassification 14P25.     

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Oxidative dehydrogenation of propane under steady-state and transient regimes over alumina-supported catalysts prepared from mixed V_2W_4O_（19）~（4-） hexametalate precursors

An integrated approach combining the development of an innovative catalyst and the research of a set of adequate operating conditions for the propane oxidative dehydrogenation (ODH) is described. The experimental set-up, specially designed for steady-state and transient studies is presented. The preparation method, the characterization and the performances in steady-state and transient regimes of catalysts based on V_2W_4O_(19)~(4-) Lindqvist isopolyanion used as a precursor and supported on alumina are reported. The influence of the preparation method of the catalyst and the role of water in the feed gas are more particularly discussed.     

Dynamical screening and ionic conductivity in water from ab initio simulations

We present a method to calculate ionic conductivities of complex fluids from ab initio simulations. This is achieved by combining density functional theory molecular dynamics simulations with polarization theory. Conductivities are then obtained via a Green-Kubo formula using time-dependent effective charges of electronically screened ions. The method is applied to two different phases of warm dense water. We observe large fluctuations in the effective charges; protons can transport effective charges greater than +e for ultrashort time scales. Furthermore, we compare our results with a simpler model of ionic conductivity in water that is based on diffusion coefficients. Our approach can be directly applied to study ionic conductivities of electronically insulating materials of arbitrary composition, e.g., complex molecular mixtures under such extreme conditions that occur deep inside giant planets.     

3D ultrasound reconstruction algorithms from analog and digital data

Freehand 3D ultrasound is increasingly being introduced in the clinic for diagnostics and image-assisted interventions. Various algorithms exist for combining 2D images of regular ultrasound probes to 3D volumes, being either voxel-, pixel- or function-based. Previously, the most commonly used input to 3D ultrasound reconstruction has been digitized analog video. However, recent scanners that offer access to digital image frames exist, either as processed or unprocessed data. To our knowledge, no comparison has been performed to determine which data source gives the best reconstruction quality. In the present study we compared both reconstruction algorithms and data sources using novel comparison methods for detecting potential differences in image quality of the reconstructed volumes. The ultrasound scanner used in this study was the Sonix RP from Ultrasonix Medical Corp (Richmond, Canada), a scanner that allow third party access to unprocessed and processed digital data. The ultrasound probe used was the L14-5/38 linear probe. The assessment is based on a number of image criteria: detectability of wire targets, spatial resolution, detectability of small barely visible structures, subjective tissue image quality, and volume geometry. In addition we have also performed the more “traditional” comparison of reconstructed volumes by removing a percentage of the input data. By using these evaluation methods and data from the specific scanner, the results showed that the processed video performed better than the digital scan-line data, digital video being better than analog video. Furthermore, the results showed that the choice of video source was more important than the choice of tested reconstruction algorithms.     

Fast solvers for discretized Navier-Stokes problems using vector extrapolation

We discuss the design and implementation of a vector extrapolation method for computing numerical solutions of the steady-state Navier-Stokes equation system. We describe a “proof of concept” implementation of vector extrapolation, and we illustrate its effectiveness when integrated into the Incompressible Flow Iterative Solution Software (IFISS) package ( http://www.manchester.ac.uk/ifiss).     

Predictive modeling of positive mode IMS gas-phase ionization: is 2nd-order Møller-Plesset perturbation theory adequate?

Low level ab initio Quantum Chemistry (QC) is shown to be a promising technique for predicting the relative ordering of a wide variety of potential analyte, dopant, and interferent molecules, by their proton affinities (PA). Computed PAs, using a single level of chemical theory, are summarized for 53 compounds and when compared to literature reference data have a mean unsigned error of ∼9.5 kJ/mol. Where applicable, multiple conformations of the protonated species were explored. In these cases, the Boltzmann weighted PA is reported. Finally, examples are shown in which QC modeling is used to predict potential fragmentation products initiated by the positive mode ionization.     

Assembly of π‐Conjugated Phosphole Azahelicene Derivatives into Chiral Coordination Complexes: An Experimental and Theoretical Study

Aza[n]helicene phosphole derivatives have been prepared from aza[n]helicene diynes by the Fagan–Nugent route. Their photophysical properties (UV/Vis absorption and emission behavior) have been evaluated. Their behavior as P,N chelates towards coordination to Pd^II and Cu^I has been investigated: metal–bis(aza[n]helicene phosphole) assemblies are formed by a highly stereoselective coordination process, as demonstrated by X‐ray crystallography. An aza[6]helicene phosphole bearing an enantiopure helicene part has been obtained, which allows the preparation of enantiopure Pd^II and Cu^I complexes with original topologies and high molar rotation (MR) and circular dichroism (CD). The structure–property relationship established from the experimental data has been studied in detail by theoretical studies (TDDFT calculations of UV/Vis, CD, and MR). Aza[n]helicene phosphole derivatives show π conjugation extended over the entire molecule, and its influence on the MR of aza[6]helicene phosphole 5 c has been demonstrated. Finally, it has been shown that the nature of the metal (coordination geometry and electronic interaction) can have a great impact on the amplitude of the chiroptical properties in metal–bis(aza[n]helicene phosphole) assemblies.