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(English) The study of the colonic volume has strong relevance in gastroenterology and contributes to the diagnosis and research of lowseverity diseases such as constipation, diarrhea, or Irritable Bowel Syndrome. In the context of these affections, the use of invasive techniques or ionizing imaging is not advisable, and the medical experts opted for Magnetic Resonance Imaging (MRI) acquired without contrast administration nor any form of patient preparation to avoid exogenous colon alteration. Specifically, two MRI modalities are of special interest: T2-weighted half-Fourier acquisition single-shot turbo spin echo sequence (T2-HASTE), which allows the segmentation of the colon lumen, and T1-weighted Fat-Sat (T1-FS), where fecal and gas contents can be distinguished. The colon analysis requires the segmentation of the colon both in T1-FS and T2-HASTE images, which is a cumbersome and timeconsuming process when performed manually. Moreover, manual segmentation involves a high degree of uncertainty in the colon boundaries delimitation, which leads to arbitrariness and poor measurement repeatability. This Ph.D. Thesis proposes an end-to-end quasi-automatic framework that comprises all the steps required to accurately segment the colon in T2-HASTE and T1-FS images, allowing the study of its morphology and the colonic content distribution. In order to ease the validation of the automated segmentation results, a tool for the synchronized T1-FS/T2-HASTE visualization has also been designed. T2-HASTE segmentation is organized as a three-stage pipeline. In the first stage, a custom tubularity filter is run to detect colon candidate areas. The specialists provide a list of points along the colon trajectory, which are combined with tubularity information to calculate an estimation of the colon medial path. In the second stage, the colon region of interest is delimited by applying custom segmentation algorithms to detect colon neighboring regions and the fat capsule containing, (Català) L'estudi del volum colònic és especialment rellevant per a la gastroenterologia i contribueix al diagnòstic i la recerca de malalties de caràcter lleu com poden ser el restrenyiment, la diarrea o la síndrome del còlon irritable. En el context d'aquestes afectacions, l'ús de tècniques invasives o ionitzants no està prou justificat i els equips mèdics han optat per l'ús d'imatges per ressonància magnètica (MRI) adquirides sense contrast ni cap altra forma de preparació, evitant així l'alteració de l'estat natural del còlon. Existeixen dues modalitats de MRI d'especial interès per a aquest propòsit: T2-weighted half-Fourier acquisition single-shot turbo spin echo sequence (T2-HASTE), que permet la segmentació del lumen del còlon, i la seqüència T1-weighted Fat-Sat (T1-FS), en la que es pot distingir el contingut fecal i el gas intestinal. L'anàlisi del còlon requereix la segmentació completa a les dues modalitats, T1-FS i T2-HASTE, el que comporta un procés manual summament lent i laboriós. Addicionalment, la segmentació manual duu associada un alt grau d'incertesa al voltant dels contorns del còlon, que es tradueix en arbitrarietat i una baixa repetitividad dels mesuraments. Aquesta tesi proposa un sistema automatitzat extrem a extrem, que inclou tots els passos necessaris per a aconseguir una segmentació de còlon precisa en imatges T2-HASTE i T1-FS, permetent l'estudi de la morfologia i la distribució dels continguts colònics. Per a facilitar la validació dels resultats de la segmentació automàtica, s'ha desenvolupat una eina per a la visualització sincronitzada de totes dues modalitats T1-FS/T2-HASTE. La segmentació d'imatges T2-HASTE és un procés constituït per tres fases. En la primera, s'utilitza un filtre de tubularidad especialitzat per a detectar àrees candidates. Els metges marquen uns punts de referència al llarg del còlon, que en combinació amb la informació de tubularidad permeten calcular una estimació de la línia medial del còlon. En una segona, (Español) El estudio del volumen colónico es especialmente relevante para la gastroenterología y contribuye al diagnóstico y a la investigación de enfermedades de carácter leve como pueden ser el estreñimiento, la diarrea o el síndrome del colon irritable. En el contexto de dichas afectaciones, el uso de técnicas invasivas o ionizantes no está suficientemente justificado y los equipos médicos han optado por el uso de imágenes por resonancia magnética (MRI) adquiridas sin contraste ni ninguna otra forma de preparación, evitando así la alteración del estado natural del colon. Existen dos modalidades de MRI de especial interés para este propósito: T2-weighted half-Fourier acquisition single-shot turbo spin echo sequence (T2-HASTE), que permite la segmentación del lumen del colon, y la secuencia T1-weighted Fat- Sat (T1-FS), en la que se pueden distinguir el contenido fecal y el gas intestinal. El análisis del colon requiere la segmentación completa en ambas modalidades, T1-FS y T2-HASTE, lo que conlleva un proceso manual sumamente lento y laborioso. Adicionalmente, la segmentación manual lleva sujeta un alto grado de incertidumbre alrededor de los contornos del colon, que se traduce en arbitrariedad y un bajo nivel de repetitividad de las mediciones. Esta tesis propone un sistema automatizado extremo a extremo, que incluye todos los pasos necesarios para conseguir una segmentación de colon precisa en imágenes T2-HASTE y T1-FS, permitiendo el estudio de la morfología y la distribución de los contenidos colónicos. Para facilitar la validación de los resultados de la segmentación automática, se ha desarrollado una herramienta para la visualización sincronizada de ambas modalidades T1-FS/T2-HASTE. La segmentación de imágenes T2-HASTE es un proceso constituido por tres fases. En la primera, se utiliza un filtro de tubularidad especializado para detectar áreas candidatas. Los médicos marcan unos puntos de referencia a lo largo del colon, que en combinación con la información, Postprint (published version)

El trasplante de órganos se ha convertido en una de las herramientas más importantes para el tratamiento de ciertas patologías en las que la disfunción de un órgano imposibilita su cura. España es líder en trasplante de órganos y su protocolo de donación se estudia y exporta a otros países. La formación de especialistas en este campo es crucial para los sistemas de salud estatales y la necesidad de encontrar formas más eficaces de realizar esta instrucción se ha incrementado en los últimos años. Una visualización de datos eficiente permite a los usuarios utilizar poderosos sistemas visuales para poder reconocer patrones de todo tipo. La evaluación inmersiva consiste en aplicar este tipo de técnicas a entornos inmersivos en realidad virtual. El objetivo principal de este TFM es crear un módulo de evaluación en RV que sirva para valorar el desempeño de los usuarios que se entrenen para el protocolo médico uDCD (Uncontrolled Donation after Circulatory determination of Death), utilizando la evaluación inmersiva para lograr exponer los resultados del entrenamiento de la manera más eficiente posible.

El trasplantament d'òrgans és una procés molt important al nostre dia a dia. Molts són els casos de salvament de vides després d'una donació d'un òrgan. Els metges que actuen durant aquests processos han d'estar altament qualificats, i avui en dia hi ha pocs països que tinguin una bona educació mèdica en aquest àmbit. Per això, una aplicació en realitat virtual, altament realista, pot ajudar a l'aprenentatge dels professionals sanitaris. Com a part d'un projecte existent, on s'hi va desenvolupar una aplicació en realitat virtual simulant el procés, aquest treball de fi de grau presenta unes millores de realisme sobre l'aplicació de simulació. S'han desenvolupat millores durant el procés d'inserció d'un catèter a l'artèria femoral i s'ha millorat i canviat l'interacció amb els objectes de l'aplicació. Es presenten els resultats d'un estudi exploratori i s'analitzen les futures branques de millora del treball., Organ transplantation is a very important process in our daily lives. There are many cases where lives are saved after organ donation. The doctors who act during these processes have to be highly qualified, and nowadays there are few countries that have a good medical education in this field. Therefore, a highly realistic virtual reality application can help healthcare professionals learn. As part of an existing project, where a virtual reality application simulating the process was developed, this thesis presents improvements in realism over the simulation application. Improvements have been developed during the process of inserting a catheter into the femoral artery and the interaction with the objects in the application has been improved and changed. The results of an exploratory study are presented and future branches of improvement of the work are discussed.

The segmentation of medical models is a complex and time-intensive process required for both diagnosis and surgical preparation. Despite the advancements in deep learning, neural networks can only automatically segment a limited number of structures, often requiring further validation by a domain expert. In numerous instances, manual segmentation is still necessary. Virtual Reality (VR) technology can enhance the segmentation process by providing improved perception of segmentation outcomes and enabling interactive supervision by experts. But inspecting how the progress of the segmentation algorithm is evolving, and defining new seeds requires seeing the inner layers of the volume, which can be costly and difficult to achieve with typical metaphors such as clipping planes. In this paper, we introduce a wedge-shaped 3D interaction metaphor designed to facilitate VR-based segmentation through detailed inspection and guidance. User evaluations demonstrated increased satisfaction with usability and faster task completion times using the tool., Research funded by PID2021-122136OB-C21 from the Ministerio de Ciencia e Innovación, Spain, by 839 FEDER (EU) funds., Peer Reviewed, Postprint (published version)

Organ transplantation has become very important for treating organ diseases and new technologies have been developed to increase the donor pool. Virtual Reality (VR) has been proven to be a valuable tool for training in medical education. This paper presents a VR application designed to simulate the medical protocol needed for the management of a deceased organ donation process called Uncontrolled Donation after Circulatory determination of Death (uDCD). Results from an explorative study on five medical experts in the area are presented, and future opportunities for improvement are discussed in the paper., Peer Reviewed, Postprint (published version)

La trasplantació d'òrgans s'ha convertit en la millor opció, i en alguns casos l'única, per al tractament de malalties d'òrgans en fase terminal. Només es cobreixen el 10% de les necessitats de trasplantament d'òrgans a tot el món cada any, la qual cosa fa de l'escassetat d'òrgans per a trasplantament un problema de salut pública. S'han desenvolupat noves tècniques a tot el món per augmentar el nombre de donants, incloent-hi la donació controlada i no controlada després de la determinació de la mort circulatòria. Gràcies a la implementació d'aquestes tècniques, Espanya i els Estats Units s'han convertit en líders mundials en donació d'òrgans de donants morts. Aquest treball de fi de grau presenta una aplicació de realitat virtual dissenyada per simular el protocol mèdic necessari per a la gestió d'un procés de donació d'òrgans de donant mort anomenat donació després d'una mort cardíaca incontrolada (uDCD). Es presenten els resultats d'un estudi exploratori realitzat amb experts mèdics en aquest àmbit i s'analitzen les futures oportunitats de millora en el treball., Organ transplantation has become the best, and in some cases the only, option for treating end stage organ diseases. Only 10% of organ transplantation requirements are covered worldwide every year, making the scarcity of organs for transplantation a public healthcare issue. New techniques have been developed worldwide to increase the donor pool, including the controlled and uncontrolled Donation after Circulatory determination of Death. By implementing these techniques, Spain and USA have become the world leaders in deceased organ donation. This final degree project presents a VR application designed to simulate the medical protocol needed for the management of a deceased organ donation process called Uncontrolled Donation after Circulatory determination of Death (uDCD). Results from an explorative study on medical experts in the area are presented, and future opportunities for improvement are discussed in the project.

In the era of the metaverse, self-avatars are gaining popularity, as they can enhance presence and provide embodiment when a user is immersed in Virtual Reality. They are also very important in collaborative Virtual Reality to improve communication through gestures. Whether we are using a complex motion capture solution or a few trackers with inverse kinematics (IK), it is essential to have a good match in size between the avatar and the user, as otherwise mismatches in self-avatar posture could be noticeable for the user. To achieve such a correct match in dimensions, a manual process is often required, with the need for a second person to take measurements of body limbs and introduce them into the system. This process can be time-consuming, and prone to errors. In this paper, we propose an automatic measuring method that simply requires the user to do a small set of exercises while wearing a Head-Mounted Display (HMD), two hand controllers, and three trackers. Our work provides an affordable and quick method to automatically extract user measurements and adjust the virtual humanoid skeleton to the exact dimensions. Our results show that our method can reduce the misalignment produced by the IK system when compared to other solutions that simply apply a uniform scaling to an avatar based on the height of the HMD, and make assumptions about the locations of joints with respect to the trackers., This work was funded by the Spanish Ministry of Science and Innovation (PID2021-122136OB-C21). Jose Luis Ponton was also funded by the Spanish Ministry of Universities (FPU21/01927)., Peer Reviewed, Postprint (published version)

The analysis of colonic contents is a valuable tool for the gastroenterologist and has multiple applications in clinical routine. When considering magnetic resonance imaging (MRI) modalities, T2 weighted images are capable of segmenting the colonic lumen, whereas fecal and gas contents can only be distinguished in T1 weighted images. In this paper, we present an end-to-end quasi-automatic framework that comprises all the steps needed to accurately segment the colon in T2 and T1 images and to extract colonic content and morphology data to provide the quantification of colonic content and morphology data. As a consequence, physicians have gained new insights into the effects of diets and the mechanisms of abdominal distension, Peer Reviewed, Postprint (published version)

Actualmente la actividad informática dentro del ámbito de la medicina está creciendo cada vez más, ya que permite ofrecer apoyo a los profesionales. En este proyecto trabajamos con datos obtenidos a partir de imágenes médicas que luego se recrean digitalmente para obtener una representación 3D. Además disponemos de una herramienta que permite recortar un objeto 3D y poder ver las partes que interesan al usuario. El objetivo de este proyecto es facilitar al usuario la identificación de la estructura anatómica de interés mediante el diseño e implementación de nuevas interacciones., Currently, computing activity within the field of medicine is growing more and more, since it allows offering support to professionals. In this project we work with data obtained from medical images that are then digitally recreated to obtain a 3D representation. We also have a tool that allows you to cut out a 3D object and see the parts that interest the user. The objective of this project is to make it easier for the user to identify the anatomical structure of interest through the design and implementation of new interactions.

The use of self-avatars in a VR application can enhance presence and embodiment which leads to a better user experience. In collaborative VR it also facilitates non-verbal communication. Currently it is possible to track a few body parts with cheap trackers and then apply IK methods to animate a character. However, the correspondence between trackers and avatar joints is typically fixed ad-hoc, which is enough to animate the avatar, but causes noticeable mismatches between the user’s body pose and the avatar. In this paper we present a fast and easy to set up system to compute exact offset values, unique for each user, which leads to improvements in avatar movement. Our user study shows that the Sense of Embodiment increased significantly when using exact offsets as opposed to fixed ones. We also allowed the users to see a semitransparent avatar overlaid with their real body to objectively evaluate the quality of the avatar movement with our technique., This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (TIN2017-88515-C2-1-R)., Peer Reviewed, Postprint (published version)

La visualización médica hace referencia al análisis y exploración sobre datos proporcionados por imágenes médicas. Los modelos volumétricos recrean digitalmente una representación volumétrica en 3D de estas imágenes. La segmentación es una técnica que permite identificar regiones diferentes entre ellas dentro de un mismo modelo. El clipping es un proceso que permite recortar parte del volumen para, de esta forma, poder visualizar partes interiores que quedan ocultas. El objetivo final de este proyecto es el diseño e implementación de nuevas herramientas que ayuden a la segmentación interactiva de un modelo volumétrico permitiendo acceder a las partes interiores del modelo volumétrico mediante una nueva herramienta de recorte., Medical visualization refers to the analysis and exploration of data provided by medical images. Volumetric models digitally recreate a 3D volumetric representation of these images. Segmentation is a technique that allows different regions to be identified within the same model. Clipping is a process that allows you to cut out part of the volume to be able to visualize parts inside the volume that are hidden. The final objective of this project is the design and implementation of new tools that help the interactive segmentation of a volumetric model allowing access to the interior parts of the volumetric model through a new clipping tool.

La Realidad Virtual es una tecnología que no para de crecer y que se ha mostrado de gran utilidad en ramas de conocimiento muy diversas. Esto se debe a su capacidad de ofrecer aproximaciones realistas del mundo que nos rodea, permitiéndonos interactuar con el entorno virtual de una forma más natural que desde un monitor. Es principalmente por esta razón que en las recientes décadas ha habido un aumento del uso de herramientas de Realidad Virtual para la educación y concretamente para la educación en ámbitos médicos. Este proyecto tiene como principal objetivo participar en ese crecimiento, añadiendo nuevas metáforas de interacción a una aplicación colaborativa e inmersiva de Realidad Virtual, desarrollada en el Centro de Realidad Virtual del grupo de investigación ViRVIG, que simula una clase de anatomía donde varios estudiantes y un profesor inspeccionan un modelo anatómico virtual. Sin embargo, pese a que la aplicación está principalmente orientada para un uso académico en anatomía, su uso es extensible para todas aquellas áreas en las que un grupo de personas deban inspeccionar e interactuar de forma conjunta con un modelo tridimensional., Virtual reality is a technology that does not stop growing and that has been shown to be very useful in very diverse branches of knowledge. This is due to its ability to offer realistic approximations of the world around us, allowing us to interact with the virtual environment in a more natural way than from a computer. It is for this reason that in recent decades there has been an increase in the use of Virtual Reality tools for education and specifically for education in medical fields. The main objective of this project is to participate in this growth, adding new interaction metaphors to a collaborative and immersive Virtual Reality application, developed at the Virtual Reality Center of the ViRVIG research group, which simulates an anatomy class where several students and a teacher inspect a virtual anatomical model. However, despite the fact that the application is mainly oriented for academic use in anatomy, its use is extensible for all those areas in which a group of people must inspect and interact with a three-dimensional model.

La motilitat del còlon és un factor que complica l'anàlisi d'aquest òrgan. Degut a les dificultats derivades dels sistemes d'extracció de dades, fins ara s'ha conegut poc sobre les relacions entre les dietes i el comportament del còlon. Tot i que és possible obtenir dades morfològiques representatives a través de la tomografia computeritzada (TC), la radiació que comporten aquestes tècniques fa que només siguin adequades per a pacients amb trastorns importants. No obstant, darrerament s'ha avançat suficientment en tècniques d'imatges extretes per ressonància magnètica (RM) com per poder obtenir dades morfològiques del còlon prou fiables a través d'aquest mètode en pacients sans, i sense exposar-los a radiacions ni medicaments. Això fa que els investigadors amb els que treballen els directors d'aquest projecte disposin d'una base de dades àmplia amb dades tant de pacients sans com amb malalties. Aquest Treball de Fi de Grau desenvolupa una aplicació web que permet als digestòlegs tenir una visualització general de les dades extretes per RM i analitzar-les i comparar-les amb dades de motilitat. Es proporcionen eines interactives i de manipulació de les dades per tal de mostrar-ne una representació personalitzada general i detallada de la base de dades, permetent l'anàlisi estadístic de les mateixes i la comparació de pacients, així com l'avaluació de possibles patrons que puguin descriure l'efecte de les dietes en el còlon., The colon motility is a factor that complicates the analysis of this organ. Due to the difficulties arising from data extraction systems, little is known so far about the relationship between diet and colon behaviour. Although it is possible to obtain representative morphological data through computerised tomography (CT), the radiation involved in these techniques makes them suitable only for patients with significant disorders. However, sufficient progress has recently been made in magnetic resonance imaging (MRI) techniques to be able to obtain sufficiently reliable morphological data of the colon through this method in healthy patients, and without exposing them to radiation or medication. This means that the researchers with whom the directors of this project are working have an extensive database with data on both healthy and sick patients. This Degree Final Project develops a web application that allows digestologists to have a general visualization of the data extracted by MRI and to analyze and compare it with motility data. It provides interactive and data manipulation tools to show a general and detailed customized representation of the database, allowing statistical analysis of the data and comparison of patients, as well as the evaluation of possible patterns that may describe the effect of diets on the colon.

Computerized Tomography (CT) and, more recently, Magnetic Resonance Imaging (MRI) have become the state-of-the art techniques for morpho-volumetric analysis of abdominal cavities. Due to its constant motility, the colon is an organ difficult to analyze. Unfortunately, CT’s radiative nature makes it only indicated for patients with important disorders. Lately, acquisition techniques that rely on the use of MRI have matured enough to enable the analysis of colon data. This allows gathering data of patients with- out preparation (i.e. administration of drugs or contrast agents), and incorporating data of patients with non life-threatening diseases and healthy subjects to databases. In this paper we present an end-to-end framework that comprises all the steps to extract colon content and morphology data coupled with a web-based visualization tool that facilitates the visual exploration of such data. We also introduce the set of tools for the extraction of morphological data, and a detailed description of a specifically-designed interactive tool that facilitates a visual comparison of numerical variables within a set of patients, as well as a detailed inspection of an individual. Our prototype was evaluated by domain experts, which showed that our visual approach may reduce the costly process of colon data analysis. As a result, physicians have been able to get new insights on the effects of diets, and also to obtain a better understanding on the motility of the colon., This project has been supported by the project TIN2017-88515-C2-1-R (GEN3DLIVE), from the Spanish Ministerio de Economía y Competitividad with FEDER (EU) funds., Peer Reviewed, Postprint (author's final draft)

L'increment de la capacitat computacional de les targetes gràfiques i l'aparició de cascs de realitat virtual a preus relativament assequibles els darrers anys, ha permès el desenvolupament i la expansió de la exploració interactiva de models volumètrics en un entorn de realitat virtual immersiva. Aquest recurs, que actualment s'usa en diversos àmbits com la medicina o el disseny industrial, presenta certs problemes. Un dels més importants és com passar dels valors d'entrada del model a la representació gràfica que veiem i com podem modificar aquesta representació interactivament. Per fer aquesta traducció s'utilitza el que es coneix com a funció de transferència, que en la seva forma més bàsica relaciona el valor d'entrada a una opacitat i color. Aquest tipus de funcions de transferència, funcionen prou bé si es defineixen abans d'explorar el model però la seva modificació interactiva durant l'exploració és bastant incòmoda. L'objectiu d'aquest projecte consisteix en comprovar si l'ús d'una metàfora d'interacció usant style transfer function, un tipus de funcions de transferència que permeten una major abstracció de les dades i presenta un acabat similar a les imatges il·lustratives dels llibres mèdics, resulta més còmode i entenedor per l'usuari que una metàfora d'interacció usant una funció de transferència unidimensional., The increase in the computing capacity of graphics cards and the emergence of virtual reality headsets at relatively affordable prices in recent years has allowed the development and expansion of interactive exploration of volumetric models in an immersive virtual reality environment. Volume models, which are currently used in various fields such as medicine or industrial design, has certain problems. One of the most important is how to move from the input values of the model to the graphical representation that we see and how we can modify this representation interactively. For establishing this correspondence, what is known as a transfer function is used, which in its most basic way relates the input value to an opacity and a color. These types of transfer functions work well if they are defined before the user explores the model in real-time, but their interactive modification during exploration is quite cumbersome. The purpose of this project is to test if the use of an interaction metaphor using style transfer function, a type of transfer function that allows for greater abstraction of data and has a similar finishing than the illustrative images of medical books, is more comfortable and user-friendly than an interaction metaphor using a one-dimensional transfer function.

The study of the colonic volume is a procedure with strong relevance to gastroenterologists. Depending on the clinical protocols, the volume analysis has to be performed on MRI of the unprepared colon without contrast administration. In such circumstances, existing measurement procedures are cumbersome and time-consuming for the specialists. The algorithm presented in this paper permits a quasi-automatic segmentation of the unprepared colon on T2-weighted MRI scans. The segmentation algorithm is organized as a three-stage pipeline. In the first stage, a custom tubularity filter is run to detect colon candidate areas. The specialists provide a list of points along the colon trajectory, which are combined with tubularity information to calculate an estimation of the colon medial path. In the second stage, we delimit the region of interest by applying custom segmentation algorithms to detect colon neighboring regions and the fat capsule containing abdominal organs. Finally, within the reduced search space, segmentation is performed via 3D graph-cuts in a three-stage multigrid approach. Our algorithm was tested on MRI abdominal scans, including different acquisition resolutions, and its results were compared to the colon ground truth segmentations provided by the specialists. The experiments proved the accuracy, efficiency, and usability of the algorithm, while the variability of the scan resolutions contributed to demonstrate the computational scalability of the multigrid architecture. The system is fully applicable to the colon measurement clinical routine, being a substantial step towards a fully automated segmentation., Postprint (author's final draft)

The colon is an organ whose constant motility poses difficulties to its analysis. Although morphological data can be successfully extracted from Computational Tomography, its radiative nature makes it only indicated for patients with disorders. Only recently, acquisition techniques that rely on the use of Magnetic Resonance Imaging have matured enough to enable the generation of morphological colon data of healthy patients without preparation (i. e. administration of drugs or contrast agents). As a result, a database of colon morphological data for patients under different diets, has been created. Currently, the digestologists we collaborate with analyze the measured data of the gut by inspecting a set of spreadsheets. In this paper, we propose a system for the exploratory visual analysis of the whole database of morphological data at once. It provides features for the visual comparison of data correlations, the inspection of the morphological measures, as well 3D rendering of the colon segmented models. The system solely relies on the use of web technologies, which makes it portable even to mobile devices., Peer Reviewed, Postprint (published version)

The analysis of the morphology and content of the gut is necessary in order to achieve a better understanding of its metabolic and functional activity. Magnetic resonance imaging (MRI) has become an important imaging technique since it is able to visualize soft tissues in an undisturbed bowel using no ionizing radiation. In the last few years, MRI of gastrointestinal function has advanced substantially. However, few studies have focused on the colon, because the analysis of colonic content is time consuming and cumbersome. This paper presents a semi-automatic segmentation tool for the quantitative assessment of the unprepared colon from MRI images. The techniques developed here have been crucial for a number of clinical experiments., Peer Reviewed, Postprint (published version)

Background: Some patients complain that eating lettuce, gives them gas and abdominal distention. Our aim was to determine to what extent the patients' assertion is sustained by evidence. Methods: An in vitro study measured the amount of gas produced during the process of fermentation by a preparation of human colonic microbiota (n = 3) of predigested lettuce, as compared to beans, a high gas-releasing substrate, to meat, a low gas-releasing substrate, and to a nutrient-free negative control. A clinical study in patients complaining of abdominal distention after eating lettuce (n = 12) measured the amount of intestinal gas and the morphometric configuration of the abdominal cavity in abdominal CT scans during an episode of lettuce-induced distension as compared to basal conditions. Key Results: Gas production by microbiota fermentation of lettuce in vitro was similar to that of meat (P = .44), lower than that of beans (by 78 ± 15%; P < .001) and higher than with the nutrient-free control (by 25 ± 19%; P = .05). Patients complaining of abdominal distension after eating lettuce exhibited an increase in girth (35 ± 3 mm larger than basal; P < .001) without significant increase in colonic gas content (39 ± 4 mL increase; P = .071); abdominal distension was related to a descent of the diaphragm (by 7 ± 3 mm; P = .027) with redistribution of normal abdominal contents. Conclusion and Inferences: Lettuce is a low gas-releasing substrate for microbiota fermentation and lettuce-induced abdominal distension is produced by an uncoordinated activity of the abdominal walls. Correction of the somatic response might be more effective than the current dietary restriction strategy., Peer Reviewed, Postprint (published version)

About 50% of the patients consulting a gastroenterology clinic report symptoms without detectable cause. Clinical researchers are interested in analyzing the volumetric evolution of colon segments under the effect of different diets and diseases. These studies require noninvasive abdominal MRI scans without using any contrast agent. In this work, we propose a colon segmentation framework designed to support T2-weighted abdominal MRI scans obtained from an unprepared colon. The segmentation process is based on an efficient and accurate quasiautomatic approach that drastically reduces the specialist interaction and effort with respect other state-of-the-art solutions, while decreasing the overall segmentation cost. The algorithm relies on a novel probabilistic tubularity filter, the detection of the colon medial line, probabilistic information extracted from a training set and a final unsupervised clustering. Experimental results presented show the benefits of our approach for clinical use., Peer Reviewed, Postprint (author's final draft)

The recent advances in VR headsets, such as the Oculus Rift or HTC Vive, at affordable prices offering a high resolution display, has empowered the development of immersive VR applications. Unfortunately, the rendering engine and the interaction devices, are not specifically designed to deal with volumetric data. In this paper we propose an immersive VR system that uses some well-known acceleration algorithms to achieve real-time rendering of volumetric datasets in an immersive VR system. Moreover, we have incorporated different basic interaction techniques to facilitate the inspection of the volume dataset. The interaction has been designed to be as natural as possible in order to achieve the most comfortable, user-friendly virtual experience. We have conducted an informal user study to evaluate the user preferences. Our evaluation shows that our application is perceived usable, easy of learn and very effective in terms of the high level of immersion achieved., Peer Reviewed, Postprint (author's final draft)

L'objectiu principal d'aquest treball de fi de grau ha sigut estudiar la viabilitat d'entorns de realitat virtual immersius per inspeccionar models anatòmics de forma col·lectiva en un entorn anàleg al d'una classe., The main objective of this bachelor's thesis has been studying the viability of immersive virtual reality environments to examine anatomic models collectively in an environment analogous to that of a classroom.

The analysis of the morphology and content of the gut is necessary in order to understand metabolic and functional gut activity and for diagnostic purposes. Magnetic resonance imaging (MRI) has become an important modality technique since it is able to visualize soft tissues using no ionizing radiation, and hence removes the need for any contrast agents. In the last few years, MRI of gastrointestinal function has advanced substantially, although scarcely any publication has been devoted to the analysis of the colon content. This paper presents a semi-automatic segmentation tool for the quantitative assessment of the unprepared colon from MRI images. This application has allowed for the analysis of the colon content in various clinical experiments. The results of the assessment have contributed to a better understanding of the functionality of the colon under different diet conditions. The last experiment carried out by medical doctors showed a marked influence of diet on colonic content, accounting for about 30% of the volume variations., Peer Reviewed, Postprint (published version)

L’objectiu global d’aquest projecte ha estat valorar la utilització d’un sistema immersiu de realitat virtual com l’HTC Vive per a la visualització i interacció de models volumètrics en aplicacions mèdiques. Per fer-ho, s’ha dissenyat i implementat un visualitzador basat en ray casting sobre la plataforma Unity 3D i s’ha optimitzat l’algorisme per obtenir-ne temps de renderitzat interactius. A més a més, s’han dissenyat i implementat tres metàfores d’interacció. Per últim, s’ha avaluat la usabilitat del sistema amb un test d’usuari que ha permès demostrar la viabilitat d’un sistema de visualització de models volumètrics en entorns de realitat virtual immersiva i identificar possibles millores per a l’aplicació desenvolupada., El objetivo global de este proyecto ha sido valorar la utilización de un sistema inmersivo de realidad virtual como el HTC Vive para la visualización e interacción de modelos volumétricos en aplicaciones médicas. Para ello, se ha diseñado e implementado un visualizador basado en ray casting sobre la plataforma Unity 3D y se ha optimizado el algoritmo para obtener tiempos de renderizado interactivos. Además, se han diseñado e implementado tres metáforas de interacción. Por último, se ha evaluado la usabilidad del sistema con un test de usuario que ha permitido demostrar la viabilidad de un sistema de visualización de modelos volumétricos en entornos de realidad virtual inmersiva e identificar posibles mejoras para la aplicación desarrollada., The overall objective of this project was to evaluate the use of an immersive virtual reality system like HTC Vive for the visualization and interaction of volumetric models in medical applications. To do this, we developed a rendering system based on ray casting and integrated into Unity3D. The algorithm has been optimized to obtain interactive rendering times. In addition, three interaction metaphors have been designed and implemented. Finally, we evaluated the usability of the system by doing a user test that proved the feasibility of a visualization system of volumetric models in immersive virtual reality environments and allowed us to identify possible improvements in the developed application.

This is the peer reviewed version of the following article: Bendezú, Á., Mego, M., Monclús, E., Merino, X., Accarino, A., Malagelada, J., Navazo, I., Azpiroz, F. Colonic content: effect of diet, meals, and defecation. "Neurogastroenterology and motility", Febrer 2017, vol. 29, núm. 2, which has been published in final form at [http://onlinelibrary.wiley.com.recursos.biblioteca.upc.edu/doi/10.1111/nmo.12930/full]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving., The metabolic activity of colonic microbiota is influenced by diet; however, the relationship between metabolism and colonic content is not known. Our aim was to determine the effect of meals, defecation, and diet on colonic content. Methods: In 10 healthy subjects, two abdominal MRI scans were acquired during fasting, 1 week apart, and after 3 days on low- and high-residue diets, respectively. With each diet, daily fecal output and the number of daytime anal gas evacuations were measured. On the first study day, a second scan was acquired 4 hours after a test meal (n=6) or after 4 hours with nil ingestion (n=4). On the second study day, a scan was also acquired after a spontaneous bowel movement. Results: On the low-residue diet, daily fecal volume averaged 145 ± 15 mL; subjects passed 10.6 ± 1.6 daytime anal gas evacuations and, by the third day, non-gaseous colonic content was 479 ± 36 mL. The high-residue diet increased the three parameters to 16.5 ± 2.9 anal gas evacuations, 223 ± 19 mL fecal output, and 616 ± 55 mL non-gaseous colonic content (P<.05 vs low-residue diet for all). On the low-residue diet, non-gaseous content in the right colon had increased by 41 ± 11 mL, 4 hours after the test meal, whereas no significant change was observed after 4-hour fast (-15 ± 8 mL; P=.006 vs fed). Defecation significantly reduced the non-gaseous content in distal colonic segments. Conclusion & inferences: Colonic content exhibits physiologic variations with an approximate 1/3 daily turnover produced by meals and defecation, superimposed over diet-related day-to-day variations., Peer Reviewed, Postprint (author's final draft)

Although Virtual Reality (VR) environments have seen slower adoption rates than expected among the medical community, throughout the last years, several new techniques and devices (e.g. Oculus Rift) have been developed that might boost the popularity of VR. However, the use of 3D environments is not exempt of some shortcomings, such as the difficulties of adaption to 3D, that sometimes produces motion sickness, or the increase in effort the user has to undergo when interacting with a 3D system, as compared to using a simple mouse on a desktop. Our proposal is tailored to focus on the second problem. More concretely, we propose a magnification technique that is able to reduce the movements required to explore a concrete part of a volumetric dataset as compared to other zooming techniques. Our technique, builds the zooming result in the same virtual position of the initial interaction while still maintaining a contextual view on the region of interest and its surroundings. This way, the user reduces the amount of movements required to explore a model and efficiency is increased. An informal user study was carried out that confirmed our hypotheses., Peer Reviewed, Postprint (published version)

This is the peer reviewed version of the following article: Bendezú, R. A., Barba, E., Burri, E., Cisternas, D., Accarino, A., Quiroga, S., Monclus, E., Navazo, I., Malagelada, J.-R. and Azpiroz, F. (2016), Colonic content in health and its relation to functional gut symptoms. Neurogastroenterol. Motil., 28: 849–854, which has been published in final form at [doi:10.1111/nmo.12782]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving, Gut content may be determinant in the generation of digestive symptoms, particularly in patients with impaired gut function and hypersensitivity. Since the relation of intraluminal gas to symptoms is only partial, we hypothesized that non-gaseous component may play a decisive role. Methods: Abdominal computed tomography scans were evaluated in healthy subjects during fasting and after a meal (n = 15) and in patients with functional gut disorders during basal conditions (when they were feeling well) and during an episode of abdominal distension (n = 15). Colonic content and distribution were measured by an original analysis program. Key results: In healthy subjects both gaseous (87 ± 24 mL) and non-gaseous colonic content (714 ± 34 mL) were uniformly distributed along the colon. In the early postprandial period gas volume increased (by 46 ± 23 mL), but non-gaseous content did not, although a partial caudad displacement from the descending to the pelvic colon was observed. No differences in colonic content were detected between patients and healthy subjects. Symptoms were associated with discrete increments in gas volume. However, no consistent differences in non-gaseous content were detected in patients between asymptomatic periods and during episodes of abdominal distension. Conclusions & inferences: In patients with functional gut disorders, abdominal distension is not related to changes in non-gaseous colonic content. Hence, other factors, such as intestinal hypersensitivity and poor tolerance of small increases in luminal gas may be involved., Peer Reviewed, Postprint (author's final draft)

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 <= .009 vs pretreatment for all). CONCLUSIONS: In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory, Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (author's final draft)

Medical doctors are often faced with the problem of selecting anchoring points in 3D space. These points are commonly used for measurement tasks, such as lengths of bones, or dimensions of pathological structures (e.g. tumours). Since previous research indicates that measurement tasks can be usually carried out more efficiently in VR environments than in desktop-based systems, we have concentrated on the development of selection tools for medical models. These models have a set of particularities such as the presence of semi-transparencies, and there is a lack of tools for measurement support for such models in VR environments. Our VR-based interaction technique uses the data to automatically generate candidate anchor points, and it is specially focused on the efficient selection of 3D points in datasets rendered using methods with semi-transparency such as Direct Volume Rendering. We will show that our method is effective, precise, and reduces the time and amount of movements required to set the anchor points as compared with other classical techniques based on clipping planes. We also provide a couple of improvements tailored to reduce the inherent imprecision of 3D devices due to hand vibration, and the flexibility in transfer function selection for anchor point definition., Peer Reviewed, Postprint (author’s final draft)

Peer Reviewed, Postprint (published version)

Advances in Medical Visualization allows the analysis of anatomical structures with the use of 3D models reconstructed from a stack of intensity-based images acquired through different techniques, being Computerized Tomographic (CT) modality one of the most common. A general medical volume graphics application usually includes an exploration task which is sometimes preceded by an analysis process where the anatomical structures of interest are first identified. The main objective of this thesis is the improvement of the user experience in the analysis and exploration of medical datasets. This improvement involves the development of efficient algorithms designed both under a user-centered perspective and taking the new computing capabilities into account in order to obtain high quality results in real-time. On the analysis stage, we have focused on the identification of the bones at joints, which is particularly challenging because the bones are very close to each other and their boundaries become ambiguous in CT images. We have concentrated our efforts on reaching maximum automation of the overall process. The proposed algorithm uses an example mesh of the same bone that has to be segmented, usually from a different person, to drive the segmentation process. The algorithm is based on an energy minimization scheme to deform the initial example mesh while following the well-defined features of the volume data to be segmented in a local and adaptive way. We also present contributions on three different aspects of the exploration task: a best-view determination system and centering in virtual reality environments, a focus-and-context technique and a point selection method. In medical practice it would often be very useful to have access to a quick pre-visualization of the involved medical dataset. We have proposed a new system which allows users to obtain a set of representative views in a short time and permits the generation of inspection paths at almost no extra cost, Els avenços en la investigació en el camp de Medical Visualization permeten l’anàlisi de models volumètrics tridimensionals d’estructures anatòmiques obtinguts a partir d’imatgesmèdiques capturades mitjançant diferents tècniques, essent la Tomografia Computeritzada (TC) una de lesmés habituals. Generalment, les aplicacions informàtiques d’ajuda al diagnòstic, la simulació, etc., permeten l’exploració interactiva d’aquest tipus de models, una tasca que pot anar precedida d’un procés d’identificació (segmentació) de les estructures anatòmiques per tal de possibilitar la seva exploració. L’objectiu d’aquesta tesi és millorar l’eficiència i l’experiència de l’usuari, tant de la tasca de segmentació com de l’exploració. Per tal d’assolir-ho s’han desenvolupat diversos algorismes; dissenyats sota una perspectiva centrada en l’usuari i fent servir els darrers avenços tecnològics de las targes gràfiques, el que ens permet obtenir resultats visuals de màxima qualitat en temps real. Respecte de la tasca de segmentació, ens hem centrat en el problema de la identificació d’ossos ubicats en articulacions, en models capturats mitjançant TC. La identificació d’aquests ossos pot arribar a ser molt feixuga i costosa fent servir les tècniques clàssiques de segmentació. La recerca realitzada en elmarc de la tesi s’ha enfocat en assolir la màxima automatització possible del procés sencer. La tècnica proposada empra una malla triangular d’exemple de l’os que es vol segmentar, que es fará servir per guiar tot el procés de segmentació. L’algorisme deforma de forma local i adaptativa aquesta malla, adaptant-la a la informació present en el model volumètric en les parts en que la seva frontera està definida de forma no ambigua, i respectant la forma original en les zones en les que el model presenta algun tipus d’incertesa en la definició de la frontera, ja sigui be perque l’estructura òssia apareix totalment unida a altres estructures òssies de l’articulació o be degut a que la informació, Los avances en la investigación en el área de Medical Visualization permiten el análisis de modelos volumétricos tridimensionales de estructuras anatómicas, los cuales se obtienen a partir de imágenes médicas capturadas mediante diferentes técnicas de captación, siendo la Tomografía Computerizada (TC) una de las más frecuentes. Habitualmente, las aplicaciones informáticas orientadas al análisis de este tipo de modelos, bien sean para el soporte al diagnóstico, simuladores médicos o la planificación de procesos quirúrgicos, permiten la exploración interactiva de los modelos volumétricos. Dependiendo de las estructuras anatómicas que se precise analizar, puede ser necesario realizar un proceso de identificación (segmentación) de las estructuras anatómicas para posibilitar su posterior inspección. El objetivo principal de esta tesis ha consistido en el desarrollo de nuevas técnicas informáticas que mejoren la experiencia del usuario en los procesos tanto de segmentación como de exploración de un modelo volumétrico. Para alcanzar dicho objetivo, ha sido necesario el desarrollo de algoritmos eficientes diseñados teniendo particularmente en cuenta al usuario final y explotando los últimos avances en la tecnología de las tarjetas gráficas para poder obtener resultados visuales de la máxima calidad en tiempo real. En lo relativo al proceso de segmentación, nos hemos centrado en la identificación de las estructuras óseas ubicadas en articulaciones, en modelos capturadosmediante TC. La identificación de este tipo de estructuras usando los métodos tradicionales de segmentación puede llegar a ser muy tediosa, debido a que puede necesitarse mucha intervención por parte del usuario. La investigación llevada a cabo ha tenido como objetivo principal el maximizar el grado de automatización en el proceso de segmentación de este tipo de estructuras. La técnica propuesta parte de un ejemplo de la estructura ósea (malla triangular) que se quiere segmentar, generada a partir de los datos, Postprint (published version)

BACKGROUND: We previously showed that abdominal distension in patients with functional gut disorders is due to a paradoxical diaphragmatic contraction without major increment in intraabdominal volume. Our aim was to characterize the pattern of gas retention and the abdomino-thoracic mechanics associated with abdominal distension in patients with intestinal dysmotility. METHODS: In 15 patients with manometrically proven intestinal dysmotility, two abdominal CT scans were performed: one during basal conditions and other during an episode of severe abdominal distension. In 15 gender- and age-matched healthy controls, a basal scan was performed. KEY RESULTS: In basal conditions, patients exhibited more abdominal gas than healthy subjects, particularly in the small bowel, and the volume significantly increased during an episode of distension. During episodes of abdominal distension, the increase in abdominal content was associated with increased girth and antero-posterior abdominal diameter, as well as a cephalic displacement of the diaphragm, which reduced the height of the lung. The consequent reduction in the air volume of the lung was attenuated by an increase in the antero-posterior diameter of the chest. CONCLUSIONS & INFERENCES: Abdominal distension in patients with severe intestinal dysfunction is related to marked pooling of gut contents, particularly in the small bowel. This increase in content is accommodated within the abdominal cavity by a global and coordinated abdomino-phreno-thoracic response, involving an accommodative ascent of the diaphragm and a compensatory expansion of the chest wall., Peer Reviewed, Postprint (published version)

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., Peer Reviewed, Postprint (published version)

In Volume Rendering, it is difficult to simultaneously visualize interior and exterior structures. Several approaches have been developed to solve this problem, such as cut-away or exploded views. Nevertheless, in most cases, those algorithms usually require either a preprocess of the data, or an accurate determination of the region of interest, previous to data inspection. In this paper we present the Virtual Magic Lantern (VML), an interaction tool tailored to facilitate volumetric data inspection. It behaves like a lantern whose virtual illumination cone provides the focal region which is visualized using a secondary transfer function or rendering style. This may be used for simple visual inspection, surgery planning, or injure diagnosis. The VML is a particularly friendly and intuitive interaction tool suitable for an immersive Virtual Reality setup with a large screen, where the user moves a Wanda device, like a lantern pointing to the model. We show that this inspection metaphor can be efficiently and easily adapted to a GPU ray casting volume visualization algorithm. We also present the Virtual Magic Window (VMW) metaphor as an efficient collateral implementation of the VML, that can be seen as a restricted case where the lantern illuminates following the viewing direction, through a virtual window created as the intersection of the virtual lantern (guided by the Wanda device) and the bounding box of the volume. This approach allows better frame rates because the shader requires almost no modification with respect to the classical volume ray casting. On the other hand, the contextual information is not perceived as well as with the previous method, especially on the boundary of the inspected region. Apart from its main use, our metaphor can also be used to aid in the tedious process of transfer function selection., Postprint (published version)

In this paper we present the Virtual Magic Lantern (VML), an interaction tool tailored to facilitate volumetric data inspection. It behaves like a lantern whose virtual illumination cone provides the focal region which is visualized using a secondary transfer function or different rendering style. This may be used for simple visual inspection, surgery planning, or injure diagnosis. The VML is a particularly friendly and intuitive interaction tool suitable for an immersive Virtual Reality setup with a large screen, where the user moves a Wanda device, like a lantern pointing to the model. We show that this inspection metaphor can be efficiently and easily adapted to a GPU ray casting volume visualization algorithm. We also present the Virtual Magic Window (VMW) metaphor as an efficient collateral implementation of the VML, that can be seen as a restricted case where the lantern illuminates following the viewing direction, through a virtual window created as the intersection of the virtual lantern (guided by the Wanda device) and the bounding box of the volume., Peer Reviewed, Postprint (author’s final draft)

Although the visualization techniques are becoming faster and faster, the datasets also increase, and the time the radiologists are able to devote to a single analysis is limited. In this sense, we propose some techniques to help the specialists to find adequate views of the datasets in an efficient way., Peer Reviewed, Postprint (author’s final draft)

Volume data models are becoming larger and larger as the capture technology improves. Thus, their visualization requires high computational power. The automatic presentation of volume models through representative images and/or exploration paths becomes more and more useful. Representative views are also useful for document illustration, fast data quality evaluation, or model libraries documentation. Exploration paths are also useful for video demonstrations and previsualization of captured data. In this paper we present a fast, adaptive method for the selection of representative views and the automatic generation of exploration paths for volume models. Our algorithm is based on multi-scale entropy and algorithmic complexity. These views and paths reveal informative parts of a model given a certain transfer function. We show that our method is simple and easy to incorporate in medical visualization tools., Postprint (author’s final draft)

Conventional treatment of the subcondylar fractures of the mandible is challenging because of the medial and anterior displacement of the condylar fragment and the limited surgical field. Proximity of facial nerve, carotid artery branches, parotid gland, and ear canal are risk factors to open surgical procedures. In these fractures a proper reduction and osteosynthesis are always difficult, even if using open procedures. The recent endoscopic approach allows a perfect control and vision of the fragments, and it also permits an anatomic reduction and plating of the fracture avoiding risks associated to the open surgery. Surgical training for these endoscopic procedures is difficult, especially in those cases in which surgeons are not familiar with endoscopic interventions and they still don’t have skills to work while looking at the screen. Simulators are friendly and risk free systems to train surgeons to operate with endoscopes., Peer Reviewed, Postprint (published version)

Poster Session: 12th Annual Conference of Iscas. Conventional treatment of the subcondylar fractures of the mandible is challenging because of the medial and anterior displacement of the condylar fragment and the limited surgical eld. Proximity of facial nerve, carotid artery branches, parotid gland, and ear canal are risk factors to open surgical procedures. In these fractures a proper reduction and osteosynthesis are always difficult, even if using open procedures. The recent endoscopic approach allows a perfect control and vision of the fragments, and it also permits an anatomic reduction and plating of the fracture avoiding risks associated to the open surgery. Surgical training for these endoscopic procedures is difficult,especially in those cases in which surgeons are not familiar with endoscopic interventions and they still don’t have skills to work while looking at the screen. Simulators are friendly and risk free systems to train surgeons to operate with endoscopes. Methods We have studied and determined the main features that a system for training of endoscopically assisted intraoral treatment of subcondylar fractures should have. We have developed a prototype system that focuses on training the surgeon in precise endoscopic examination and tools manipulation. In order to do this, we have created a virtual 3D model of a fractured mandible from the CT data of a real patient. Images were segmented semi-automatically and the noise generated by the capture process has been eliminated. We have opted by a hybrid model of surface and volume that eases the movement of structures and realistic volume renderings. The system allows simulating an interactive inspection of the fracture with a straight or a 30 degrees telescope, by rendering onto screen a similar image to the generated by a real telescope. Jointly with the model we may also visualize some surgical tools. The system incorporates additional functionalities that help the medical doctor understanding the re, Peer Reviewed

Volume data models are becoming larger and larger as the capture technology improves. Thus, their visualization requires high computational power. The automatic presentation of volume models through representative images and/or exploration paths becomes more and more useful. Representative views are also useful for document illustration, fast data quality evaluation, or model libraries documentation. Exploration paths are also useful for video demonstrations and previsualization of captured data. In this paper we present a fast, adaptive method for the selection of representative views and the automatic generation of exploration paths for volume models. Our algorithm is based on multi-scale entropy and algorithmic complexity. These views and paths reveal informative parts of a model given a certain transfer function. We show that our method is simple and easy to incorporate in medical visualization tools., Peer Reviewed