B-Spline Snakes: A Flexible Tool for Parametric Contour Detection

We present a novel formulation for B-spline snakes that can be used as a tool for fast and intuitive contour outlining. We start with a theoretical argument in favor of splines in the traditional formulation by showing that the optimal, curvature-constrained snake is a cubic spline, irrespective of the form of the external energy field. Unfortunately, such regularized snakes suffer from slow convergence speed because of a large number of control points, as well as from difficulties in determining the weight factors associated to the internal energies of the curve. We therefore propose an alternative formulation in which the intrinsic scale of the spline model is adjusted a priori; this leads to a reduction of the number of parameters to be optimized and eliminates the need for internal energies (i.e., the regularization term). In other words, we are now controlling the elasticity of the spline implicitly and rather intuitively by varying the spacing between the spline knots. The theory is embedded into a multi-resolution formulation demonstrating improved stability in noisy image environments. Validation results are presented, comparing the traditional snake using internal energies and the proposed approach without internal energies, showing the similar performance of the latter. Several biomedical examples of applications are included to illustrate the versatility of the method

Centered Pyramids

Quadtree-like pyramids have the advantage of resulting in a multiresolution representation where each pyramid node has four unambiguous parents. Such a centered topology guarantees a clearly defined up-projection of labels. This concept has been successfully and extensively used in applications of contour detection, object recognition and segmentation. Unfortunately, the quadtree-like type of pyramid has poor approximation powers because of the employed piecewise-constant image model. This paper deals with the construction of improved centered image pyramids in terms of general approximation functions. The advantages of the centered topology such a symmetry, consistent boundary conditions and accurate up-projection of labels are combined with a more faithful image representation at coarser pyramid levels. We start by introducing a general framework for the design of least squares pyramids using the standard filtering and decimation tools. We give the most general explicit formulas for the computation of the filter coefficients by any (well behaving) approximation function in both the continuous $(L _{ \infty } )$ and the discrete $(l _{ \infty } )$ norm. We then define centered pyramids and provide the filter coefficients for odd spline approximation functions. Finally, we compare the centered pyramid to the ordinary one and highlight some applications

Multiresolution Approximation Using Shifted Splines

We consider the construction of least squares pyramids using shifted polynomial spline basis functions. We derive the pre- and post-filters as a function of the degree n and the shift parameter Δ. We show that the underlying projection operator is entirely specified by two transfer functions acting on the even and odd signal samples, respectively. We introduce a measure of shift-invariance and show that the most favorable configuration is obtained when the knots of the splines are centered with respect to the grid points (i.e., Δ=1/2 when n is odd, and Δ=0 when n is even). The worst case corresponds to the standard multiresolution setting where the spline spaces are nested

Variational guidewire tracking using phase congruency

We present a novel method to track a guidewire in cardiac x-ray video. Using variational calculus, we derive differential equations that deform a spline, subject to intrinsic and extrinsic forces, so that it matches the image data, remains smooth, and preserves an a priori length. We analytically derive these equations from first principles, and show how they include tangential terms, which we include in our model. To address the poor contrast often observed in x-ray video, we propose using phase congruency as an image-based feature. Experimental results demonstrate the success of the method in tracking guidewires in low contrast x-ray video

Code of conduct for scientific integrity

The scientific landscape has changed considerably since the Swiss Academies of Arts and Sciences published Integrity in scientific research: Principles and procedures in 2008. Consequently, an expert group was set up with members from the Swiss Academies of Arts and Sciences, the Swiss National Science Foundation, swissuniversities, and Innosuisse to review the changes that have taken place in recent years and to draw up this Code of conduct for scientific integrity. This Code is aimed at everyone involved in the generation, dissemination, and advancement of knowledge within the Swiss higher education system. This includes scientists, institutions, and funding organisations. Institutions and funding organisations have a special role to play in creating and maintaining the conditions in which scientific integrity can thrive. Scientific integrity is based on the observance of fundamental principles and their many different contextual concretisations. These principles guide scien- tists in their research and teaching and help them to deal with the practical, ethical, and intellectual challenges they can expect to encounter. The aim of this code of conduct is to promote appropriate attitudes and to help build a robust culture of scientific integrity that will stand the test of time. Ethical scientific behaviour rests on the basic principles of reliability, honesty, respect, and accountability and supports the concretisations of these basic principles within a specific frame of reference. This Code is intended to be a dynamic document. Its aim is to strengthen scientific integrity in all avenues of research and education, with a particular emphasis on the training and development of young people. Another of its aims is to establish a culture of research integrity in the scientific community, with the Code providing a welcome framework rather than imposing its own set of rules. It promotes common understanding and parity of treatment in dealing with violations of scientific integrity within and between institutions. The Code also considers current developments in the fields of Open Science and social media, and it examines the issue of time limitation from several points of view. In addition, it offers practical recommendations on how to set up an organisation for the protection of scientific integrity and describes the processes involved

Synthesis of Fluorine-18 Functionalized Nanoparticles for use as in vivo Molecular Imaging Agents

Nanoparticles containing fluorine-18 were prepared from block copolymers made by ring opening metathesis polymerization (ROMP). Using the fast initiating ruthenium metathesis catalyst (H_2IMes)(pyr)_2(Cl)_2Ru=CHPh, low polydispersity amphiphilic block copolymers were prepared from a cinnamoyl-containing hydrophobic norbornene monomer and a mesyl-terminated PEG-containing hydrophilic norbornene monomer. Self-assembly into micelles and subsequent cross-linking of the micelle cores by light-activated dimerization of the cinnamoyl groups yielded stable nanoparticles. Incorporation of fluorine-18 was achieved by nucleophilic displacement of the mesylates by the radioactive fluoride ion with 31% incorporation of radioactivity. The resulting positron-emitting nanoparticles are to be used as in vivo molecular imaging agents for use in tumor imaging

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG2000cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems

International Pediatric ORL Group (IPOG) laryngomalacia consensus recommendations

Objective To provide recommendations for the comprehensive management of young infants who present with signs or symptoms concerning for laryngomalacia. Methods Expert opinion by the members of the International Pediatric Otolaryngology Group (IPOG). Results Consensus recommendations include initial care and triage recommendations for health care providers who commonly evaluate young infants with noisy breathing. The consensus statement also provides comprehensive care recommendations for otolaryngologists who manage young infants with laryngomalacia including: evaluation and treatment considerations for commonly debated issues in laryngomalacia, initial work-up of infants presenting with inspiratory stridor, treatment recommendations based on disease severity, management of the infant with feeding difficulties, post-surgical treatment management recommendations, and suggestions for acid suppression therapy. Conclusion Laryngomalacia care consensus recommendations are aimed at improving patient-centered care in infants with laryngomalacia

Chronic Cough and Eosinophilic Esophagitis: An Uncommon Association

An increasing number of children, usually with gastrointestinal symptoms, is diagnosed with eosinophilic esophagitis (EE), and a particular subset of these patients complains of airway manifestations. We present the case of a 2-year-old child with chronic dry cough in whom EE was found after a first diagnosis of gastroesophageal reflux disease (GERD) due to pathological 24-hour esophageal pH monitoring. Traditional allergologic tests were negative, while patch tests were diagnostic for cow's milk allergy. We discuss the intriguing relationship between GERD and EE and the use of patch test for the allergologic screening of patients

The High Radiosensitizing Efficiency of a Trace of Gadolinium-Based Nanoparticles in Tumors

International audienceWe recently developed the synthesis of ultrasmall gadolinium-based nanoparticles (GBN), (hydrodynamic diameter <5 nm) characterized by a safe behavior after intravenous injection (renal clearance, preferential accumulation in tumors). Owing to the presence of gadolinium ions, GBN can be used as contrast agents for magnetic resonance imaging (MRI) and as radiosensitizers. The attempt to determine the most opportune delay between the intravenous injection of GBN and the irradiation showed that a very low content of radiosensitizing nanoparticles in the tumor area is sufficient (0.1 μg/g of particles, i.e. 15 ppb of gadolinium) for an important increase of the therapeutic effect of irradiation. Such a promising and unexpected result is assigned to a suited distribution of GBN within the tumor, as revealed by the X-ray fluorescence (XRF) maps