Real-time Interobserver Agreement in Bowel Ultrasonography for Diagnostic Assessment in Patients With Crohn's Disease:An International Multicenter Study

Background The unavailability of standardized parameters in bowel ultrasonography (US) commonly used in Crohn's disease (CD) and the shortage of skilled ultrasonographers are 2 limiting factors in the use of this imaging modality around the world. The aim of this study is to evaluate interobserver agreement among experienced sonographers in the evaluation of bowel US parameters in order to improve standardization in imaging reporting and interpretation. Methods Fifteen patients with an established diagnosis of CD underwent blinded bowel US performed by 6 experienced sonographers. Prior to the evaluation, the sonographers and clinical and radiological IBD experts met to formally define the US parameters. Interobserver agreement was tested with the Quatto method (s). Results All operators agreed on the presence/absence of CD lesions and distinguished absence of/mild activity or moderate/severe lesions in all patients. S values were moderate for bowel wall thickness (s = 0.48, P = n.s.), bowel wall pattern (s = 0.41, P = n.s.), vascularization (s = 0.52, P = n.s.), and presence of lymphnodes (s = 0.61, P = n.s.). Agreement was substantial for lesion location (s = 0.68, P = n.s.), fistula (s = 0.74, P = n.s.), phlegmon (s = 0.78, P = 0.04), and was almost perfect for abscess (s = 0.95, P = 0.02). Poor agreement was observed for mesenteric adipose tissue alteration, lesion extent, stenosis, and prestenotic dilation. Conclusions In this study, the majority of the US parameters used in CD showed moderate/substantial agreement. The development of shared US imaging interpretation patterns among sonographers will lead to improved comparability of US results among centers and facilitate the development of multicenter studies and the spread of bowel US training, thereby allowing a wider adoption of this useful technique

Predictive regularity representations in deviance detection and auditory stream segregation: from conceptual to computational models

Predictive accounts of perception have received increasing attention in the past twenty years. Detecting violations of auditory regularities, as reflected by the Mismatch Negativity (MMN) auditory event-related potential, is amongst the phenomena seamlessly fitting this approach. Largely based on the MMN literature, we propose a psychological conceptual framework called the Auditory Event Representation System (AERS), which is based on the assumption that auditory regularity violation detection and the formation of auditory perceptual objects are based on the same predictive regularity representations. Based on this notion, a computational model of auditory stream segregation, called CHAINS, has been developed. In CHAINS, the auditory sensory event representation of each incoming sound is considered for being the continuation of likely combinations of the preceding sounds in the sequence, thus providing alternative interpretations of the auditory input. Detecting repeating patterns allows predicting upcoming sound events, thus providing a test and potential support for the corresponding interpretation. Alternative interpretations continuously compete for perceptual dominance. In this paper, we briefly describe AERS and deduce some general constraints from this conceptual model. We then go on to illustrate how these constraints are computationally specified in CHAINS

Structural and dynamical properties of aqueous suspensions of NaPSS (HPSS) at very low ionic strength

PACS. 51.20.+d Viscosity, diffusion, and thermal conductivity - 78.35.+c Brillouin and Rayleigh scattering; other light scattering - 82.70.Kj Emulsions and suspensions,

Electric field light scattering by flexible linear polyelectrolytes in aqueous solution

Electric field light scattering results on aqueous solutions of linear, flexible NaPSS at minimal ionic strength are reported. Samples of molecular weights between 356 kg/mol and 2870 kg/mol were investigated. With increasing field strength the intensity as a function of wavenumber develops a pronounced oscillating behaviour. Besides the well-known first peak a second maximum is observed at the position at which a weak maximum for some samples already occurs at zero field. The overall intensity strongly depends on the frequency of the electric field. The electro-optical effect shows a maximum at 300 kHz. Increasing the particle concentration gives a large increase of the peak maximum, normalized to concentration. If plotted versus scattering angle the relative intensity increase is maximum for samples of medium molecular weight. The results strongly indicate a stretching and alignment of the chains, thus leading to or enlarging the short range order of the chains

Characterization of Poly(styrenesulfonate) at Minimum Ionic Strength by Electric and Magnetic Birefringence Experiments

Results of birefringence experiments on aqueous solutions of charged poly (styrenesulfonate) (PSS) with different molecular weights between $10^5$ and $1.1\times 10^6$ g/mol in external electric and magnetic fields are presented. Most of our studies are carried out on solutions of minimum ionic strength (down to $\approx 10^{-6}$ M), under conditions where the particles are surrounded by extended counterion clouds. The PSS particles can be nearly completely oriented in high electric fields ($>10^5$ V/m) and the saturation value of the birefringence is obtained. In low electric fields a Kerr behavior is found and we are able to determine the electric anisotropy $\Delta\alpha_{\rm el}(=\alpha_{\rm el,||}-\alpha_{\rm el,\perp})$ of a single particle caused by the anisotropic polarization of the counterion cloud. At low particle concentrations $c$, this cloud (respectively the electric anisotropy) decreases like $c^{-1/2}$ with increasing concentration. Rising this concentration once more leads to a decrease of the Kerr constant $(k\propto \Delta\alpha_{\rm el}.l_{\rm p}$, where $l_{\rm p}$ is the persistence length characterizing flexible polymers) faster than $c^{-1/2}$ pointing out a starting coiling expressed by a lowering of the persistence length. In the electric birefringence experiment we are limited to particle concentrations between $5\times 10^{-4}$ and 5 mg/ml wherefore we complemented our studies by high magnetic field experiments ($0<B<16.8$ T) at higher concentrations ($10<c<75$ mg/ml). The mechanism orienting PSS particles in magnetic fields is much weaker than that in electric fields. Therefore no full alignment of our polyelectrolytes is possible, all measurements are done in the Cotton-Mouton regime. This is the first investigation of the persistence length of poly(styrenesulfonate) at minimum ionic strength over a wide concentration regime

Electric Field Light Scattering by Rod-Like Polyelectrolytes in Aqueous Suspensions

Static light scattering measurements are presented for rod-like fd-virus particles ($L=880$ nm, $D= 9$ nm) subjected to a pulsed alternating electric field in aqueous suspensions at very low ionic strength. In aqueous suspensions the dispersed fd-particles are negatively charged and surrounded by a diffuse Debye counterion cloud. In an external electric field an induced dipole originating from a deformation of the diffuse counterion cloud causes the alignment of the macromolecules. The anisotropic orientation distribution of the particles in the presence of the electric field results in a change of the angular distribution of the scattered light intensity with regard to the isotropic case. The steady-state electric field light scattering effect $\Delta I/I_0$ is measured as a function of the electric field strength and its frequency at a fixed scattering angle. The determination of the anisotropy of the electric polarizability $\Delta\alpha_{\rm el}$ of a fd-virus particle at higher electric field strengths, above the Kerr regime, shows a decrease of $\Delta\alpha_{\rm el}$ with increasing field. This is interpreted as a destruction of the diffuse Debye cloud in high electric fields. The orientational order parameter has been found to be as large as 0.93 indicating an almost complete particle orientation along the external field at the highest fields. It is also shown that in the frequency regime below 1 kHz electrostatically interacting rods can align perpendicular to the external electric field, whereas at higher frequencies this anomalous behaviour disappears. From the scattered intensity the form-factor and the static structure factor of interacting fd-virus particles have been determined. With increasing fields a substantial increase in the peak height of the static structure factor is found. The data is in good agreement with Monte Carlo simulations using a simple interaction model for the system. The orientation of the macromolecules in the presence of an electric field is affected by the intermolecular electrostatic repulsion