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Los trastornos respiratorios del sueno, en particular el sindrome de apneas e hipopneas durante el sueno (SAHS), son frecuentes en la poblacion infantil (su prevalencia se ha estimado en un 1-3%) y su causa mas frecuente es la hipertrofia adenoamigdalar. Estan infradiagnosticados y se asocian a importantes complicaciones, tales como alteraciones del crecimiento, alteraciones cognitivas e incluso, en casos graves, cor pulmonale. La polisomnografia nocturna es la tecnica diagnostica de eleccion para el diagnostico del SAHS en los ninos, pero en la poblacion infantil es necesario tener en cuenta una serie de consideraciones, como la edad y el entorno adecuado. Ademas, los criterios diagnosticos del SAHS para adultos no son utiles. El tratamiento de eleccion en los ninos con SAHS es la adenoamigdalectomia, que es curativa en un 70% de los casos.

Virtual Reality (VR) Systems allow immersive inspection of very complex environments, with direct interaction with the objects in the virtual scene. Low cost and affordable VR systems are becoming essential in application areas like Industrial Design, Medical Applications and Cultural Heritage and require sophisticated techniques for model inspection and interaction. Discrete geometric models can be very useful for some involved geometry processing algorithms like model repair, occlusion culling and multi-resolution and level of detail. The interest of these techniques and their potential in present and future VR applications will be discussed. This paper addresses the interest of discrete geometric models in volume-based geometric simplification, the use of discrete tiles for impostorbased extreme simplification, topology preserving model repair techniques based on discrete membranes and specific algorithms for recovering polygonal shapes from discrete volume models. The use of out-of-core octree...

Background: The precise relation of intestinal gas to symptoms, particularly abdominal bloating and distension remains incompletely elucidated. Our aim was to define the normal values of intestinal gas volume and distribution and to identify abnormalities in relation to functional-type symptoms. Methods:Abdominal computed tomography scans were evaluated in healthy subjects (n = 37) and in patients in three conditions: basal (when they were feeling well; n = 88), during an episode of abdominal distension (n = 82) and after a challenge diet (n = 24). Intestinal gas content and distribution were measured by an original analysis program. Identification of patients outside the normal range was performed by machine learning techniques (one-class classifier). Results are expressed as median (IQR) or mean ± SE, as appropriate. Key Results: In healthy subjects the gut contained 95 (71, 141) mL gas distributed along the entire lumen. No differences were detected between patients studied under asymptomatic basal conditions and healthy subjects. However, either during a spontaneous bloating episode or once challenged with a flatulogenic diet, luminal gas was found to be increased and/or abnormally distributed in about one-fourth of the patients. These patients detected outside the normal range by the classifier exhibited a significantly greater number of abnormal features than those within the normal range (3.7 ± 0.4 vs 0.4 ± 0.1; p < 0.001). Conclusions & Inferences: The analysis of a large cohort of subjects using original techniques provides unique and heretofore unavailable information on the volume and distribution of intestinal gas in normal conditions and in relation to functional gastrointestinal symptoms.

OBJECTIVE: The objective of this study was to evaluate the diagnostic reliability of home respiratory polygraphy (HRP) in children with a clinical suspicion of OSA-hypopnea syndrome (OSAS). METHODS: A prospective blind evaluation was performed. Children between the ages of 2 to 14 years with clinical suspicion of OSAS who were referred to the Sleep Unit were included. An initial HRP followed by a later date, same night, in-laboratory overnight respiratory polygraphy and polysomnography (PSG) in the sleep laboratory were performed. The apnea-hypopnea index (AHI)-HRP was compared with AHI-PSG, and therapeutic decisions based on AHI-HRP and AHI-PSG were analyzed using intraclass correlation coefficients, Bland-Altman plots, and receiver operator curves (ROCs). RESULTS: Twenty-seven boys and 23 girls, with a mean age of 5.3 ± 2.5 years, were studied, and 66% were diagnosed with OSAS based on a PSG-defined obstructive respiratory disturbance index ≥ 3/h total sleep time. Based on the availability of concurrent HRP-PSG recordings, the optimal AHI-HRP corresponding to the PSG-defined OSAS criterion was established as ≥ 5.6/h The latter exhibited a sensitivity of 90.9% (95% CI, 79.6%-100%) and a specificity of 94.1% (95% CI, 80%-100%). CONCLUSIONS: HRP recordings emerge as a potentially useful and reliable approach for the diagnosis of OSAS in children. However, more research is required for the diagnosis of mild OSAS using HRP in children.

BACKGROUND & AIMS: In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients. METHODS: We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment. RESULTS: Episodes of abdominal distension were associated with diaphragm contraction (19% +/- 3% increase in EMG score and 12 +/- 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% +/- 3% increase in EMG scores and 6 +/- 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 +/- 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 +/- 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% +/- 2%) and the diaphragm (by 18% +/- 4%), activated the internal oblique muscles (by 52% +/- 13%), and reduced girth (by 25 +/- 3 mm) (P

Resumen Los liposarcomas raramente se asientan en la cabeza y cuello. Presentamos un caso de un liposarcoma mixoide retrofaringeo remitido por presentar un sindrome de apneas-hipopneas obstructivas durante el sueno.

Remote exploration of medical volume models is nowadays a challenging problem. Interactive visualization algorithms must be able to send and render in real-time the volume model at the maximum possible visual quality, while adapting to network bandwidth limitations and to hardware constraints in the client device. In this paper we present a transfer function-aware scheme for the remote interactive inspection of volume models in client-server architectures with the objectives of supporting multi-resolution, avoiding gradient computations in the client device and sending a very limited amount of information through the network. Gradient Octrees can be progressively transmitted to the clients in a strongly compact way while achieving a minimum loss of visual quality as compared to state of the art ray-casting renderings. Visual volume understanding can be complemented by showing 2D sections of the original volume data on demand.

This paper describes VolDmi, an open system for volume modeling and visualization defined as an interactive platform which will integrate current and future research developments, as well as specific applications. The article begins with the analysis of the main functional modules of the system. Then, the design criteria which have been followed are explained and the system's global operation is described, with special emphasis on user interaction. Subsequently, the central kernel of the system is presented. This kernel is mainly composed of input/output modules along with creation and operation modules for a generalized voxel-model. Finally, the default visualization of the voxel-model that has been implemented in the system and which is based on the slice stacking algorithm, is presented.

Medical illustrations have been used for a long time for teaching and communicating information for diagnosis or surgery planning. Illustrative visualization systems create methods and tools that adapt traditional illustration techniques to enhance the result of renderings. Clipping the volume is a popular operation in volume rendering for inspecting the inner parts, though it may remove some information of the context that is worth preserving. In this paper we present a new editing technique based on the use of clipping planes, direct structure extrusion, and illustrative methods, which preserves the context by adapting the extruded region to the structures of interest of the volumetric model. We will show that users may interactively modify the clipping plane and edit the structures to highlight, in order to easily create the desired result. Our approach works with segmented volume models and non-segmented ones. In the last case, a local segmentation is performed on-the-fly. We will demonstrate the efficiency and utility of our method. © 2012 Wiley Periodicals, Inc.

The visualization of volumetric datasets, quite common in medical image processing, has started to receive attention fromother communities such as scientific and engineering. The main reason is that it allows the scientists to gain important insights into the data. While the datasets are becoming larger and larger, the computational power does not always go hand to hand, because the requirements of using low-end PCs or mobile phones increase. As a consequence, the selection of an optimal viewpoint that improves user comprehension of the datasets is challenged with time consuming trial and error tasks. In order to facilitate the exploration process, informative viewpoints together with camera paths showing representative information on the model can be determined. In this paper we present amethod for representative viewselection and path construction, togetherwith some accelerations that make this process extremely fast on a modern GPU.

The present paper addresses the problem of detecting closed compartments produced by a set of planar faces in the space. The topology of the set is general, and edges in the final piecewise planar surface can belong to one, two or more faces; boundary representations for non-manifold solids are an example. An octree structure (dubbed eightit compartment Octree) that defines a 3D graph through the volume defined by the set of faces is proposed, and it is shown that a seed propagation algorithm on the graph can be used to detect the existing closed compartments. The algorithm can either compute the total number of compartments or detect if the set of faces define a closed solid volume, the outside part being considered as a separate compartment.

Objective Overnight polysomnography (PSG) is thegold standard diagnostic tool for sleep apnea-hypopneasyndrome (SAHS) in children. The aim of the present studywas to evaluate the usefulness of diagnostic respiratorypolygraphy in children with clinically suspected SAHSreferred to our sleep-disordered breathing clinic. Patients and Methods We studied 53 children referredwith clinical suspicion of SAHS; 29 (54.7%) were boys andthe mean (SD) age was 6.4 (2.9) years. After a medicalhistory was taken and a physical examination performed, patients underwent respiratory polygraphy (Edentec)simultaneously with overnight PSG in the sleep laboratory. The 2 diagnostic tools were compared using statisticalanalysis. Results SAHS was defined by an obstructive apnea-hypopnea index (OAHI) of 3 or more in overnight PSG anda respiratory disturbance index (RDI) of 3 or more inrespiratory polygraphy. The rate of diagnostic agreementwas 84.9%. The difference between the mean OAHI andRDI values was not significant (0.7 [5.4]; P =.34). Theintraclass correlation coefficient between the OAHI andRDI was 89.4 (95% confidence interval, 82.4-93.7; P When receiver operating characteristic curves werecalculated for the OAHI cutoff points used for the diagnosisof SAHS (1, 3, and 5), the best RDI cutoff for all 3 OAHI valuesconsidered was found to be 4.6. When age strata wereconsidered, in children 6 years or older the best RDI cutofffor the 3 OAHI values was 2.1. In children younger than 6 years the best RDI cutoff was 3.35 for OAHI 1 and 5.85 forOAHI 3 and 5. Conclusions Respiratory polygraphy in the sleeplaboratory is a valid method for the diagnosis of SAHS inchildren.

Solid modelers must be based on reliable and fast algorithms for Boolean operations. The octree model, as well as several generalizations (polytrees, integrated polytrees, extended octrees), is specially well suited for these algorithms and can be used either as a primary or as a secondary model in solid modeling systems. This paper is concerned with a precise definition of the extended octree model that allows the representation of nonmanifold objects with planar faces and, consequently, is closed under Boolean operations on polyhedrons. Boolean nodes and nearly vertex nodes are introduced, and the model is discussed in comparison with related representations. A fast algorithm for the direct generation of the extended octree from the geometry of the base polygon in extrusion solids is presented, and its complexity is studied. Boolean operation algorithms are introduced.

Liposarcomas rarely occur in the head and neck. We report a case of myxoid liposarcoma occurring in the retropharyngeal space in a middle-aged male with clinical symptoms of obstructive sleep apnoea.

When using data-capture methods designed to retrieve functional information, we may have incomplete morphological information in the presence of desease. This is specially so for SPECT data of an infarcted heart.

Level-of-detail occlusion culling is a novel approach to the management of occluders that can be easily integrated into most current visibility culling algorithms. The main contribution of this paper is an algorithm that automatically generates sets of densely overlapping boxes with enhanced occlusion properties from non-convex subsets. We call this method occluder synthesis because it is not sensitive to the way the objects are tesselated but to the space enclosed by them. The extension of this technique by allowing a bounded amount of image error is also discussed. We show that visibility computations can be based on a multiresolution model which provides several representations of these occluders with varying visibility accuracy. Our tests show that occlusion performance in tesselated scenes is improved severely even if no image-error is allowed.

This work is focused on the interactive navigation through highly polygon-populated ship environments. A conservative visibility algorithm is presented that hierarchically computes visibility for different observer positions and stores it in a new octree based structure, the Visibility Octree (VO) The VO is used during the navigation. Its main contribution is the ability to provide an effective control over the coarseness of the visibility approximation. Some results are presented for indoor ship scenes that show that the VO is efficient on densely occluded scenes.

Multiresolution models with different levels of detail are a basic tool for handling very large and complex systems in computer aided design applications such as ship design. In this work, we discuss several automatic simplification algorithms that generate a multiresolution family of solid models that approximate with different levels of detail the boundary representation of a given polyhedral solid. Methods based on the simplification of triangular meshes are discussed together with octree based algorithms. Comparison criteria include the possibility of geometry and topology simplification, the availability of approximation bounds and feature preservation.

When scenes with a large number of elements have to be used, it is difficult to do a real time walk-through. An algorithm to compute a weak visibility graph of a large data set based on its discretization by means of a regular uniform grid is introduced. The algorithm computes the visibility graph using a new approach for the cell to cell visibility test and an auxiliary quad-tree to speed up.

Introduction Attended overnight polysomnography (PSG) performed in a sleep laboratory is the currently accepted technique used for the diagnosis of sleep apnea/hipopnea syndrome (SAHS) in children. Respiratory Polygraphy (RP) in children has been validated in the sleep laboratory. AIM: To evaluate the reliability diagnostic of home respiratory Polygraph (HRP) in children with a clinical suspicion of SAHS referred to one sleep unit. Materials and methods Cross-sectional study. We included children aged 2–14 years, of both sexes, with clinical suspicion of SAHS referred to the Sleep Unit on randomly selected days. The whole group underwent clinical history, physical examination, a first home respiratory polygraphy (HRP) and between 1 and 2 weeks later underwent a second PR and PSG in the same night in sleep laboratory. The criteria of the AASM 2007 were used for the assessment of sleep and respiratory events. We calculated the normal index of RP and PSG: Respiratory disturbance index (RDI), Obstructive respiratory disturbance index (oRDI) Obstructive Apnea-Hypopneas Obstructive index (oAHI). Intraclass correlation coefficients (ICC), Bland-Altman plots and receiver operator curves (ROC) were calculated for statistical analysis. We calculated confidence intervals at 95%. Results We studied 27 boys and 23 girls with a mean age of 5.3 (SD: 2.55). 39 (78%), 33 (66%), 26 (52%) were diagnosed with SAHS, when RDI ⩾ 3, oRDI ⩾ 3 and OAHI ⩾ 3 were taken as diagnosis of SAHS. The average of RDI was 13.92 (SD16, 57), 14.46 (SD: 13.23), 16.47 (SD: 15.32) in the PSG, Home RP, RP at laboratory respectively. The area under the ROC curve for RDI ⩾ 3, oRDI ⩾ 3 and OAHI ⩾ 3 in the laboratory RP were 93.5 (85.5 - 1), 96.8 (92.1 - 1), 95, 5 (90.6 - 1) and in the HRP were 93.5 (86.8 - 1), 93.9 (87.0 - 1), 92.9 (85.9 - 1), respectively. Conclusion Home respiratory polygraphy has a good agreement with the values of the PSG Respiratory Poligraphy performed at home is a useful technique for diagnosis of SAHS in children. Acknowledgements Funded by Ministry of Health Castilla – Leon and SEPAR.

Computer graphics education is becoming more and more relevant in technical studies in Spain. This positive evolution is partly due to the changes in the curricula structure in the undergraduate studies in Spain in recent years. New and updated curricula are being set up in most universities with a semester structure for their courses. As a consequence, a good number of computer graphics courses have been created, and the number of universities offering graphics courses has clearly increased.Due to the converging interests in computer graphics education, a Computer Graphics Education Group has existed within the Spanish chapter of the Eurographics Association since 1992. The main activities of the group include annual meetings to discuss curricula, covered topics, methodology and resources. Relevant information and support materials are accessible and shared through the Internet ( http://smagris.eleinf.uv.es/DOCEN-CIA_IG/docencia.html ).Undergraduate university studies in Spain are either technical (three years) or high (five years). Most of the computer graphics courses are offered in both curricula. Graduate courses are organized in Ph.D. programs. Ph.D. programs in computer graphics are emerging as the new universities settle their studies. In the next two sections we briefly summarize the organization and contents of the computer graphics courses in Spain.

This paper describes the authors experience in the organization and teaching of courses of Computer Graphics for both undergraduate and graduate students. Curriculum contents and teaching methodologies are discussed, taking into account practical constraints related to the facilities available at laboratories and curriculum structures.

An approximate octree representation for closed surfaces is presented, namely face octrees. Face Octrees are based on a hierarchical representation of the subdivision of the space, until either homogeneous or face nodes are reached. Face nodes contain a connected, sufficiently planar part of the surface, within a tolerance s. The face octree of a surface S defines a thick surface TS(S), union of all bands defined by face nodes, and TS(S) contains S; a band in a face node spans e to both sides of the plane n approximating S in the node. An algorithm for the generation of the octree, based on the clipping of the surface patches and a planarity test, is presented. On the other hand, algorithms are proposed for point-solid classification, line and plane intersection tests, and interference detection. Space complexity of the proposed representation is discussed, and some bounds are presented.

In this paper, the visualization of hybrid scenes that contain volume data and a fitted extracted surface is addressed. The proposed algorithm is based on a integrated octree-based representation: the “hybrid octree.” The hybrid octree allows to obtain multiresolution representation of the volume data and it also maintains a decimated surface codification. The proposed visualization approach uses three-dimensional-textures for the visualization of the volume data and integrates the surface polygons using the information represented in the octree structure. The main characteristics of the method are: its capabilities to perform multiresolution hybrid visualizations and its efficient use of texture memory space.

Most visibility culling algorithms require convexity of occluders. Occluder synthesis algorithms attempt to construct large convex occluders inside bulky non-convex sets. Occluder fusion algorithms generate convex occluders that are contained in the umbra cast by a group of objects given an area light. In this paper we prove that convexity requirements can be shifted from the occluders to their umbra with no loss of efficiency, and use this property to show how some special non-planar, non-convex closed polylines that we call "hoops" can be used to compute occlusion efficiently for objects that have no large interior convex sets and were thus rejected by previous approaches.

Occlusion culling and level-of-detail rendering have become two powerful tools for accelerating the handling of very large models in real-time visualization applications. We present a framework to combine both techniques that improves rendering times. Classical occlusion culling algorithms compute potentially visible sets (PVS), overestimations of the sets of visible polygons. The novelty of our approach is to estimate the degree of visibility of each object of the PVS using different level-of-detail for the occluders. This allows to arrange the objects of each PVS into several Hardly-Visible Sets (HVS) by similar occlusion percentage. According to image accuracy and frame ratio requirements, HVS provide a way to avoid sending to the graphics pipeline those objects whose pixel contribution is low due to partial occlusion. The image loss can be bounded by the user at navigation time. On the other hand, as HVS offers a tighter estimation of the pixel contribution for each scene object it can be used for a more convenient selection of the level-of-detail at which objects are rendered. In this paper, we describe the new framework technique, provide details of its implementation using a visibility octree as the chosen occlusion culling data structure and show some experimental results on the image quality.

Given a tetrahedral mesh immersed in a voxel model, we present a method to refine the mesh to reduce the discrepancy between interpolated values based on either scheme at arbitrary locations. An advantage of the method presented is that it requires few subdivisions and all decisions are made locally at each tetrahedron. We discuss the algorithm’s performance and applications.

Since the publication of the original Marching Cubes algorithm, numerous variations have been proposed for guaranteeing water-tight constructions of triangulated approximations of iso-surfaces. Most approaches divide the 3D space into cubes that each occupies the space between eight neighboring samples of a regular lattice. The portion of the iso-surface inside a cube may be computed independently of what happens in the other cubes, provided that the constructions for each pair of neighboring cubes agree along their common face. The portion of the iso-surface associated with a cube may consist of one or more connected components, which we call sheets. We distinguish three types of decisions in the construction of the iso-surface connectivity: (1) how to split the X-faces, which have alternating in/out samples, (2) how many sheets to use in a cube, and (3) how to triangulate each sheet. Previously reported techniques make these decisions based on local criteria, often using pre-computed look-up tables or simple construction rules. Instead, we propose global strategies for optimizing several topological and combinatorial measures of the isosurfaces: triangle count, genus, and number of shells. We describe efficient implementations of these optimizations and the auxiliary data structures developed to support them.

Interactive visualization of volume models in standard mobile devices is a challenging present problem with increasing interest from new application fields like telemedicine. The complexity of present volume models in medical applications is continuously increasing, therefore increasing the gap between the available models and the rendering capabilities in low-end mobile clients. New and efficient rendering algorithms and interaction paradigms are required for these small platforms. In this paper, we propose a transfer function-aware compression and interaction scheme, for client-server architectures with visualization on standard mobile devices. The scheme is block-based, supporting adaptive ray-casting in the client. Our two-level ray-casting allows focusing on small details on targeted regions while keeping bounded memory requirements in the GPU of the client. Our approach includes a transfer function-aware compression scheme based on a local wavelet transformation, together with a bricking scheme that supports interactive inspection and levels of detail in the mobile device client. We also use a quantization technique that takes into account a perceptive metrics of the visual error. Our results show that we can have full interaction with high compression rates and with transmitted model sizes that can be of the order of a single photographic image.