Regular triangulations of dynamic sets of points

The Delaunay triangulations of a set of points are a class of triangulations which play an important role in a variety of different disciplines of science. Regular triangulations are a generalization of Delaunay triangulations that maintain both their relationship with convex hulls and with Voronoi diagrams. In regular triangulations, a real value, its weight, is assigned to each point. In this paper a simple data structure is presented that allows regular triangulations of sets of points to be dynamically updated, that is, new points can be incrementally inserted in the set and old points can be deleted from it. The algorithms we propose for insertion and deletion are based on a geometrical interpretation of the history data structure in one more dimension and use lifted flips as the unique topological operation. This results in rather simple and efficient algorithms. The algorithms have been implemented and experimental results are given.Postprint (published version

Two triangulations methods based on edge refinement

In this paper two curvature adaptive methods of surface triangulation are presented. Both methods are based on edge refinement to obtain a triangulation compatible with the curvature requirements. The first method applies an incremental and constrained Delaunay triangulation and uses curvature bounds to determine if an edge of the triangulation is admissible. The second method uses this function also in the edge refinement process, i.e. in the computation of the location of a refining point, and in the re-triangulation needed after the insertion of this refining point. Results are presented, comparing both approachesPostprint (published version

Skeletal representations of orthogonal shapes

In this paper we present two skeletal representations applied to orthogonal shapes of R^n : the cube axis and a family of skeletal representations provided by the scale cube axis. Orthogonal shapes are a subset of polytopes, where the hyperplanes of the bounding facets are restricted to be axis aligned. Both skeletal representations rely on the L∞ metric and are proven to be homotopically equivalent to its shape. The resulting skeleton is composed of n − 1 dimensional facets. We also provide an efficient and robust algorithm to compute the scale cube axis in the plane and compare the resulting skeleton with other skeletal representations.Postprint (published version

A practical and robust method to compute the boundary of three-dimensional axis-aligned boxes

The union of axis-aligned boxes results in a constrained structure that is advantageous for solving certain geometrical problems. A widely used scheme for solid modelling systems is the boundary representation (Brep). We present a method to obtain the B-rep of a union of axis-aligned boxes. Our method computes all boundary vertices, and additional information for each vertex that allows us to apply already existing methods to extract the B-rep. It is based on dividing the three-dimensional problem into two-dimensional boundary computations and combining their results. The method can deal with all geometrical degeneracies that may arise. Experimental results prove that our approach outperforms existing general methods, both in efficiency and robustness.)Peer ReviewedPostprint (author’s final draft

From Degenerate Patches to Triangular and Trimmed Patches

Postprint (published version

Splat representation of parametric surfaces

Point-based geometry representations and their splat-based generalizations have become a suitable technique both for modeling and rendering complex 3D shapes. So, it seems interesting to convert other kind of models to a point or splat-based representations. In this work, we present an approach to convert a parametric surface to an elliptical splat-based representation. Although this conversion supposes a loss of information going from an analytical to an approximate model, it will allow to locally modify zones with complex features, to mix surface and splat-based models and to take advantage of the existing point-based rendering methods. The presented approach works in the parametric space and performs an adaptive sampling based on the surface curvature and a given error tolerance. The goal is to obtain an optimized set of elliptical splats that completely covers the surface. Two strategies are presented, one based on a quadrangular subdivision of the parametric space and the other on power Voronoi diagrams. Finally, some open problems are enumerated.Postprint (published version

Skin lesions in neurofibromatosis type 2 : diagnostic and prognostic significance of cutaneous (plexiform) schwannomas

Acord transformatiu CRUE-CSICBackground: Neurofibromatosis type 2 (NF2) is a genetic disease characterized by the appearance of multiple tumours in the nervous system. Cutaneous lesions are common and may provide useful diagnostic and prognostic information, but they have not been widely studied. Objectives: To characterize cutaneous lesions in a Spanish cohort of patients with NF2 and investigate associations with clinical and genetic severity. Methods: We studied the clinical and histologic characteristics of cutaneous lesions in 49 patients with NF2 and analysed correlations with phenotype- and genotype-based severity scores. We collected information on the presence/absence of cutaneous lesions, location, age at onset, type of lesion, and histologic features. We also studied level of systemic involvement and genetic mutations involved. Results: Forty-nine patients (31 women [63.3%] and 18 men [36.7%]) were analysed, and 33 (67.3%) had cutaneous lesions presumed to be schwannomas. According to their clinical form, they were distributed as follows: 24 patients (48%) had deep tumours, 21 (42%) had plaque-like lesions, and 3 (6%) had superficial tumours. Histologic examination from 27 lesions analysed out 23 patients showed classic schwannoma or hybrid schwannoma-neurofibroma features in the 8 deep tumours biopsied and plexiform schwannoma features in the 17 plaque-like lesions and the 2 superficial tumours analysed. Early onset (first 2 decades of life) was reported by all patients with plaques and superficial tumours. In our cohort, 100% of the patients with plaque-like lesions and superficial tumours with microscopic features of plexiform schwannoma were in the 2 groups with the most severe clinical phenotypes, and 82.6% of them were in the 3 most severe genotype-based classes. Conclusions and Relevance: Cutaneous lesions, specially plexiform schwannomas, are common in NF2, and they usually appear at an early age providing useful diagnostic and prognostic information. These tumours are part of the spectrum of cutaneous manifestations in this disease. Although its diagnostic and prognostic value has been pointed out, there are few studies focussed on their analysis

Skeleton computation of an image using a geometric approach

In this work we develop two algorithms to compute the skeleton of a binary 2D images. Both algorithms follow a geometric approach and work directly with the boundary of the image wich is an orthogonal polygon (OP). One of these algorithms processes the edges of the polygon while the other uses its vertices. Compared to a thinning method, the presented algorithms show a good performance.Postprint (published version

Evaluation of a New Digital Automated Glycemic Pattern Detection Tool

Background: Blood glucose meters are reliable devices for data collection, providing electronic logs of historical data easier to interpret than handwritten logbooks. Automated tools to analyze these data are necessary to facilitate glucose pattern detection and support treatment adjustment. These tools emerge in a broad variety in a more or less nonevaluated manner. The aim of this study was to compare eDetecta, a new automated pattern detection tool, to nonautomated pattern analysis in terms of time investment, data interpretation, and clinical utility, with the overarching goal to identify early in development and implementation of tool areas of improvement and potential safety risks. Methods: Multicenter web-based evaluation in which 37 endocrinologists were asked to assess glycemic patterns of 4 real reports (2 continuous subcutaneous insulin infusion [CSII] and 2 multiple daily injection [MDI]). Endocrinologist and eDetecta analyses were compared on time spent to analyze each report and agreement on the presence or absence of defined patterns. Results: eDetecta module markedly reduced the time taken to analyze each case on the basis of the emminens eConecta reports (CSII: 18 min; MDI: 12.5), compared to the automatic eDetecta analysis. Agreement between endocrinologists and eDetecta varied depending on the patterns, with high level of agreement in patterns of glycemic variability. Further analysis of low level of agreement led to identifying areas where algorithms used could be improved to optimize trend pattern identification. Conclusion: eDetecta was a useful tool for glycemic pattern detection, helping clinicians to reduce time required to review emminens eConecta glycemic reports. No safety risks were identified during the study

Guia d'antídots per als centres d’urgències d’atenció primària de Catalunya

Intoxicació aguda; Emergències toxicològiques; Serveis d'urgènciesIntoxicación aguda; Emergencias toxicológicas; Servicios de urgenciasAcute intoxication; Toxicological emergencies; Emergency servicesEl document que presentem a continuació correspon a la primera edició de la Guia d’antídots per als centres d’urgències d’atenció primària de Catalunya, elaborada per un grup de treball multidisciplinari integrat per metges i farmacèutics del Grup d’Antídots de la Societat Catalana de Farmàcia Clínica (SCFC) i de la Direcció General d’Ordenació i Regulació Sanitària (DGORS) del Departament de Salut. En aquesta primera edició s’han inclòs els antídots actualment comercialitzats, així com els productes de descontaminació i les recomanacions de disponibilitat qualitativa i quantitativa en els CUAP. Així mateix, s’ha incorporat informació sobre les principals indicacions toxicològiques, la posologia i les vies d’administració, juntament amb informació relativa a les reaccions adverses i advertències sobre l’embaràs i la lactància