M.C. Juan

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.

Using augmented reality to treat phobias

Virtual reality (VR) is useful for treating several psychological problems, including phobias such as fear of flying, agoraphobia, claustrophobia, and phobia to insects and small animals. We believe that augmented reality (AR) could also be used to treat some psychological disorders. AR and VR share some advantages over traditional treatments. However, AR gives a greater feeling of presence (the sensation of being there) and reality judgment (judging an experience as real) than VR because the environment and the elements the patient uses to interact with the application are real. Moreover, in AR users see their own hands, feet, and so on, whereas VR only simulates this experience. With these differences in mind, the question arises as to the kinds of psychological treatments AR and VR are most suited for. In our system, patients see their own hands, feet, and so on. They can touch the table that animals are crossing or seeing their feet while the animals are running on the floor. They can also hold a marker with a dead spider or cockroach or pick up a flyswatter, a can of insecticide, or a dustpan.

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 pigs liver.

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.

An augmented reality system for treating psychological disorders: application to phobia to cockroaches

Augmented reality has been used in many fields, but it has not been used to treat psychological disorders. Augmented reality presents several advantages respect to: the traditional treatment of psychological disorders and virtual reality treatments. In this paper we present the first augmented reality system for the treatment of phobia to cockroaches. Our system has been developed using ARToolkit software. It has been tested with one patient and the results have been very satisfactory. At first of the exposure session the patient was not able to approach to a real cockroach and after the exposure session using our augmented reality system, the patient was able to approach to a real cockroach, to interact with it and to kill it by herself. This first result is very encouraging and it demonstrates that augmented reality exposure is effective for the treatment of this kind of phobias.

Contact model, fit process and, foot animation for the virtual simulator of the footwear comfort

This paper describes the new advances carried out for Simucal. Simucal was introduced in [13] and it is a footwear virtual simulator designed to perform studies of comfort and functionality in CAD footwear design. In this paper, a new finite element model for the deformation of shoe upper materials in gait is presented. This model provides a physical interpretation from the point of view of the contact mechanics to the previous model used in Simucal, as well as the new form of the problem allows that new materials and models can be easily computed. This paper also presents a wider description of the simulator, specifying the main tasks of the two main programs included in Simucal such as the initial fit performed by the Aligner. Finally, the process carried out to obtain the feet animation database is described.

VR-mirror: a virtual reality system for mental practice in post-stroke rehabilitation

Developments in basic neurological research and techniques used to train professional athletes suggest that one way of facilitating this learning process of motor schemas is through the use of motor imagery, a training technique in which the procedure required to perform a task is mentally rehearsed in absence of actual physical movement. Clinical studies have shown that rehabilitation of hemiplegic and hemiparetic patients can be improved by integrating physical and mental practice. In this paper, we describe an advanced virtual reality workbench, the VR- Mirror, that it has been designed to support stroke patients with upper-limb hemiplegia in generating motor images. The development of this prototype has been supported by the Commission of the European Communities (CEC) – IST programme (Project I-Learning, IST 2001-38861).

The memory book

In this paper we present an Augmented Reality book for remembering past events and to plan future ones. We have developed this system using Brainstorm eStudio. We have incorporated Augmented Reality options into Brainstorm eStudio using a plugin of ARToolKit. The user can create his own book selecting images, objects and videos from a database. The selection of elements and their inclusion into the book is achieved using a tangible interface.

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.

Deformable brain atlas: Validation of the location of subthalamic nucleus using T1-weighted MR images of patients operated on for Parkinson’s

Parkinsons disease is a degenerative disease of the central nervous system. One of the most effective treatments is deep brain stimulation. This technique requires the localization of an objective structure: the subthalamic nucleus. Unfortunately this structure is difficult to locate. In this work the creation of a deformable brain atlas that enables the identification of the subthalamic nucleus in T1-weighted magnetic resonance imaging (MRI) in an automatic, precise and fast way is presented. The system has been validated using data from 10 patients (20 nucleus) operated on for Parkinsons. Our system offers better results using a Wendland function with an error of 1.8853+/-0.9959mm.