Biomedical subjects

M Alcañiz

Publications and source records attributed to M Alcañiz.

16 recordsLinked to original sources

PubMed2005

Real-time deformable models for surgery simulation: a survey.

Simulating the behaviour of elastic objects in real time is one of the current objectives of computer graphics. One of its fields of application lies in virtual reality, mainly in surgery simulation systems. In computer graphics, the models used for the construction of objects with deformable behaviour are known as deformable models. These have two conflicting characteristics: interactivity and motion realism. The different deformable models developed to date have promoted only one of these (usually interactivity) to the detriment of the other (biomechanical realism). In this paper, we present a classification of the different deformable models that have been developed. We present the advantages and disadvantages of each one. Finally, we make a comparison of deformable models and perform an evaluation of the state of the art and the future of deformable models.

Biomechanical Phenomena↗

PubMed2005

Mixing realities? An application of augmented reality for the treatment of cockroach phobia.

Augmented reality (AR) refers to the introduction of virtual elements in the real world. That is, the person is seeing an image composed of a visualization of the real world, and a series of virtual elements that, at that same moment, are super-imposed on the real world. The most important aspect of AR is that the virtual elements supply to the person relevant and useful information that is not contained in the real world. AR has notable potential, and has already been used in diverse fields, such as medicine, the army, coaching, engineering, design, and robotics. Until now, AR has never been used in the scope of psychological treatment. Nevertheless, AR presents various advantages. Just like in the classical systems of virtual reality, it is possible to have total control over the virtual elements that are super-imposed on the real world, and how one interacts with those elements. AR could involve additional advantages; on one side it could be less expensive since it also uses the real world (this does not need to be modeled), and it could facilitate the feeling of presence (the sensation of being there), and reality judgment (the fact of judging the experience as real) of the person since the environment he or she is in, and what he or she is seeing is, in fact the "reality." In this paper, we present the data of the first case study in which AR has been used for the treatment of a specific phobia, cockroaches phobia. It addresses a system of AR that permits exposure to virtual cockroaches super-imposed on the real world. In order to carry out the exposure, the guidelines of Ost with respect to "one-session treatment" were followed. The results are promising. The participant demonstrated notable fear and avoidance in the behavioral avoidance test before the treatment, and not only was an important decrease in the scores of fear and avoidance observed after the treatment, but also the participant was capable of approaching, interacting, and killing live cockroaches immediately following the treatment. The results are maintained in a follow-up conducted 1 month after the termination of the treatment.

Adult↗

PubMed2004

Immersion and emotion: their impact on the sense of presence.

The present study is designed to test the role of immersion and media content in the sense of presence. Specifically, we are interested in the affective valence of the virtual environments. This paper describes an experiment that compares three immersive systems (a PC monitor, a rear projected video wall, and a head-mounted display) and two virtual environments, one involving emotional content and the other not. The purpose of the experiment was to test the interactive role of these two media characteristics (form and content). Scores on two self-report presence measurements were compared among six groups of 10 people each. The results suggest that both immersion and affective content have an impact on presence. However, immersion was more relevant for non-emotional environments than for emotional ones.

Adolescent↗

PubMed2004

Improved watershed transform for medical image segmentation using prior information.

The watershed transform has interesting properties that make it useful for many different image segmentation applications: it is simple and intuitive, can be parallelized, and always produces a complete division of the image. However, when applied to medical image analysis, it has important drawbacks (oversegmentation, sensitivity to noise, poor detection of thin or low signal to noise ratio structures). We present an improvement to the watershed transform that enables the introduction of prior information in its calculation. We propose to introduce this information via the use of a previous probability calculation. Furthermore, we introduce a method to combine the watershed transform and atlas registration, through the use of markers. We have applied our new algorithm to two challenging applications: knee cartilage and gray matter/white matter segmentation in MR images. Numerical validation of the results is provided, demonstrating the strength of the algorithm for medical image segmentation.

Algorithms↗

PubMed2003

GeRTiSS: Generic Real Time Surgery Simulation.

Minimally invasive surgery is a technique that permits interventions through very small incisions. This minimises the patients' trauma and permits a faster recovery in comparison with classical surgery. The disadvantage of this surgery technique, though, is its complexity, requiring a high training effort of the surgeon. In this paper, we present a general surgery simulator for training surgeons in minimally invasive surgery. The application allows to create environments and interaction modes very similar to those encountered in real surgical interventions. The virtual environments are optionally composed of an actual patient's organs the intervention on which one desires to practice in a beforehand manner, or of synthetically generated organs with arbitrary pathologies. The intervention is carried out by means of haptic interfaces with force feedback, providing the surgeon with a sense of touch, a fundamental element of all types of surgery.

Computer Simulation↗

PubMed2002

The VEPSY UPDATED project: technical and clinical rationale.

The emergence of new shared media, such as the Internet and virtual reality are changing the ways in which people relate, communicate, and live. Health care, and in particular clinical psychology, is one of the areas that could be most dramatically reshaped by these new technologies. To exploit and understand this potential is the overall goal of the "Telemedicine and Portable Virtual Environment in Clinical Psychology"--VEPSY UPDATED--an European Community funded research project (IST-2000-25323, http://www.vepsy.com) whose specific goal is the development of different PC based virtual reality modules to be used in clinical assessment and treatment. In particular the developed modules have been using to address the following pathologies: anxiety disorders; male impotence and premature ejaculation; obesity, bulimia and binge-eating disorders. The chapter details the general technical and clinical characteristics of the developed modules.

Diagnosis, Computer-Assisted↗

PubMed2001

Automatic localization of cephalometric Landmarks.

A system for automatic detection of cephalometric landmarks is presented. Landmark detection is carried out in two steps: a line detection module searches for significant, well-contrasted lines of the image, such as the jaw line or the nasal spine. The landmark detection module uses the lines located in the first module to determine the search areas and then applies a pattern detection algorithm, based on mathematical morphology techniques. Relations between landmarks and lines are determined by means of a training process. The system has been tested for the detection of 17 landmarks on 20 images: more than 90% of the landmarks are accurately identified.

Algorithms↗

PubMed2001

A new approach for the real-time simulation of tissue deformations in surgery simulation.

Simulation of the behaviour of elastic objects in real time is one of the present objectives of computer graphics. One of its fields of application lies in virtual reality, mainly in surgery simulation systems. Models used for the construction of objects with deformable behaviour in computer graphics are known as deformable models. These have two conflicting characteristics: interactivity and movement realism. The deformable models developed up till now have promoted one characteristic to the detriment of the other. In this paper, a new approach is proposed based on boundary element methods (BEM). This is characterised by a positive equilibrium between speed and realism and great robustness. These properties along with the experimental results described in this paper permit one to assert that establishing deformable models with BEM is a reliable method to model objects in virtual reality environments for surgery simulation. In addition to that, the required elasticity parameters could be obtained experimentally through the use of a pig's liver.

Algorithms↗

PubMed2001

The VEPSY updated project: virtual reality in clinical psychology.

Many of us grew up with the naive assumption that couches are the best used therapeutic tools in psychotherapy. But tools for psychotherapy are evolving in a much more complex environment than a designer's chaise lounge. In particular, virtual reality (VR) devices have the potential for appearing soon in many consulting rooms. The use of VR in medicine is not a novelty. Applications of virtual environments for health care have been developed in the following areas: surgical procedures (remote surgery or telepresence, augmented or enhanced surgery, and planning and simulation of procedures before surgery); preventive medicine and patient education; medical education and training; visualization of massive medical databases; and architectural design for health care facilities. However, there is a growing recognition that VR can play an important role in clinical psychology, too. To exploit and understand this potential is the main goal of the Telemedicine and Portable Virtual Environment in Clinical Psychology--VEPSY Updated--a European Community-funded research project (IST-2000-25323, http://www.vepsy.com). The project will provide innovative tools-telemedicine and portable-for the treatment of patients, clinical trials to verify their viability, and action plans for dissemination of its results to an extended audience-potential users and influential groups. The project will also develop different personal computer (PC)-based virtual reality modules to be used in clinical assessment and treatment. In particular, the developed modules will address the following pathologies: anxiety disorders; male impotence and premature ejaculation; and obesity, bulimia, and binge-eating disorders.

Adult↗

PubMed2000

Multiresolution segmentation of three-dimensional medical images using mathematical morphology techniques.

A semi-automatic method for three-dimensional segmentation of medical images is proposed. A multiresolution representation is achieved through the application of morphological filters, which assures causality for image extrema. This allows for a compact scale space representation, in which each extremum is assigned a scale value. Interactive selection of the interesting extrema of the image is carried out, aided by this scale information and other relevant features. Extrema selected are then used as markers in three-dimensional watersheds calculation. The system has been developed and tested under low cost platforms, and can be the base for totally automatic, knowledge based segmentation systems.

Artificial Intelligence↗

PubMed2000

A new efficient method for 3D registration using human brain atlases.

In this article a new efficient method in deformable brain atlases is proposed. To achieve this goal we use the composition of two applications, an affine transformation and other one. In this second application we have used three different approaches. One approach that has been used and two new approaches. We use a set of points to be identified both in brain atlas and in patient's brain for registration. The three approach present an advantage: the mathematical solution obtained makes it to be very fast, almost immediate. Several results have been obtained and they have been classified as very satisfactory by the neurosurgeons that have tested our system.

Brain Mapping↗

PubMed1999

Interactive image-guided surgery system with high-performance computing capabilities on low-cost workstations: a prototype.

We present a new frameless stereotatic system prototype that has been initially validated in functional neurosurgery operations and that makes use of an optical position tracker for image-guided neurosurgery. Several devices for tracking different surgical instruments have been designed and manufactured. These devices include an array of infrared light-emitting diodes that are tracked by three charge-coupled device cameras. The system presents several new approaches for surgery planning. For high-quality 3D images of the patient's anatomy, we have developed a parallel version of a volume-rendering algorithm, thus enabling real-time 3D anatomy manipulation on low-cost PC workstations. In order to test the accuracy of the system, the localization of the target by means of a stereotatic frame has been compared with frameless techniques, obtaining a difference of about 1 +/- 1 mm.

Algorithms↗

PubMed1999

A system for the simulation and planning of orthodontic treatment using a low cost 3D laser scanner for dental anatomy capturing.

The detection and correction of malocclusions and other dental abnormalities is a significant area of work in orthodontic diagnosis. To assess the quality of occlusion between the teeth the orthodontist has to estimate distances between specific points located on the teeth of both arches. Distance measuring is based on the observation, by the orthodontist, of a plaster model of the mouth. Gathering of information required to make the diagnosis is a time consuming and costly operation. On the other hand, obtaining and manipulation of plaster casts constitute a huge problem in clinics, due to both the large space needed and high costs associated with plaster casts manufacturing. For this problem we present a new system for three-dimensional orthodontic treatment planning and movement of teeth. We describe a computer vision technique for the acquisition and processing of three-dimensional images of the profile of hydrocolloids dental imprints taken by mean of a own developed 3D laser scanner. Profile measurement is based on the triangulation method which detects deformation of the projection of a laser line on the dental imprints. The system is computer-controlled and designed to achieve depth and lateral resolutions of 0.1 mm and 0.2 mm, respectively, within a depth range of 40 mm. The developed diagnosis software system (named MAGALLANES) and the 3D laser scanner (named 3DENT) are both commercially available and have been designed to replace manual measurement methods, which use costly plaster models, with computer measurements methods and teeth movement simulation using cheap hydrocolloid dental wafers. This procedure will reduce the cost and acquisition time of orthodontic data and facilitate the conduct of epidemiological studies.

Adult↗

PubMed1998

Virtual reality treatment of claustrophobia: a case report.

The efficacy of a treatment for claustrophobia using only Virtual Reality (VR) exposure was examined. The subject was a 43-year-old female who suffered from clinically significant distress and impairment and sought psychological therapy. Eight individual VR graded exposure sessions were conducted. All self-report measures were reduced following VR exposure and were maintained at one month follow-up. The necessity of a theoretical framework for this new medium for exposure therapy is discussed.

Adult↗

PubMed1998

An advanced system for the simulation and planning of orthodontic treatment.

This paper presents a new system for three-dimensional (3-D) orthodontic treatment planning and movement of teeth. We describe a computer vision technique for the acquisition and processing of 3-D images of the profile of hydrocolloid dental imprints. Profile measurement is based on the triangulation method which detects deformation of the projection of a laser line on the dental imprints. The system is computer-controlled and designed to achieve depth and lateral resolutions of 0.1 and 0.2 mm, respectively, within a depth range of 40 mm. The 3-D image of the imprint is segmented in order to identify different teeth. Two operators are presented: one for the detection of molars and premolars based on a directional gradient, and one for incisors and canines based on 3-D registration with dental models contained in a database. We apply these 3-D dental models to simulate the 3-D movement of teeth, including rotations, during orthodontic treatment. With this objective, we have developed an original simplified model of arch-wire behaviour and a viscoplastic behaviour law for the alveolar bone in order to simulate teeth displacements during orthodontic treatment. The contribution of the paper is part of a diagnosis system (called MAGALLANES) that is designed to replace manual measurement methods, which use costly plaster models, with computer measurement methods and teeth movement simulation using cheap hydrocolloid dental wafers. This procedure will reduce the cost and acquisition time of orthodontic data and facilitate the conduct of epidemiological studies.

Biomechanical Phenomena↗

PubMedDate not supplied

Computer-aided periodontal disease diagnosis using computer vision.

Periodontal diseases are the major cause of tooth loss. The study of the evolution of these diseases is crucial to achieve adequate planning and treatment. Depth probing is essential to know the periodontal disease stage. In this paper we present a new system for Computer-Aided Periodontal Disease Diagnosis using computer vision. The system automates the depth probing and incorporates a colour camera fitted together with a plastic probe that automatically and exactly obtains the depth probing measure. The system has been tested by several periodontists and with 125 teeth of different patients. The differences between the values taken by the system and two periodontists have not been significant.

Absorptiometry, Photon↗