Miguel A. Padilla Castañeda

Local Autonomous Robot Navigation Using Potential Fields

The potential fields method for autonomous robot navigation consists essentially in the assignment of an attractive potential to the goal point and a repulsive potential to each of the obstacles in the environment. Several implementations of potential fields for autonomous robot navigation have been reported. The most simple implementation considers a known environment where fixed potentials can be assigned to the goal and the obstacles. When the obstacles are unknown the potential fields have to be adapted as the robot advances, and detects new obstacles. The implementation of the potential fields method with one attraction potential assigned to the goal point and fixed repulsion points assigned to the obstacles, has the important limitation that for some obstacle configurations it may not be possible to produce appropriate resultant forces to avoid the obstacles. Recently the use of several adjustable attraction points, and the progressive insertion of repulsion points as obstacles are detected online, have proved to be a viable method to avoid large obstacles using potential fields in environments with unknown obstacles. In this chapter we present the main characteristics of the different approaches to implement local robot navigation algorithms using potential fields for known and partially known environments. Different strategies to escape from local minima, that occur when the attraction and repulsion forces cancel each other, are also considered.

Deformable model of the prostate for TURP surgery simulation

Abstract During a prostatectomy, a surgeon removes the inner prostate tissue that obstructs the urinary flow. The standard procedure, called transurethral resection of the prostate (TURP), is a minimally invasive surgery in which a resectoscope is introduced through the urethra of the patient to remove the obstructing tissue. In this paper, we present a three-dimensional (3D) computer model of the prostate for TURP simulation. The prostate model is designed to be the basis of a computer simulator for TURP training. The model was built from a set of ultrasound images with a technique that constructs a 3D volumetric mesh of the prostate shape, which is able to closely reproduce tissue resections as they are performed during real TURP procedures. A mass-spring method is used to model tissue deformation due to surgical tool interaction. The model simulates, in real-time: resections; tissue deformations; the cavity produced by the user as the surgical procedure progresses; and the corresponding reduction of the prostate volume.

Autonomous robot navigation based on the evolutionary multi-objective optimization of potential fields

This article presents the application of a new multi-objective evolutionary algorithm called RankMOEA to determine the optimal parameters of an artificial potential field for autonomous navigation of a mobile robot. Autonomous robot navigation is posed as a multi-objective optimization problem with three objectives: minimization of the distance to the goal, maximization of the distance between the robot and the nearest obstacle, and maximization of the distance travelled on each field configuration. Two decision makers were implemented using objective reduction and discrimination in performance trade-off. The performance of RankMOEA is compared with NSGA-II and SPEA2, including both decision makers. Simulation experiments using three different obstacle configurations and 10 different routes were performed using the proposed methodology. RankMOEA clearly outperformed NSGA-II and SPEA2. The robustness of this approach was evaluated with the simulation of different sensor masks and sensor noise. The scheme reported was also combined with the wavefront-propagation algorithm for global path planning.

Resection Simulation with Local Tissue Deformations for Computer Assisted Surgery of the Prostate

We present a three-dimensional anatomical and deformable model of the prostate for prostatectomy simulation. The model was build from a set of ultrasound images with the prostate contour, automatically annotated, with a technique based on a genetic algorithm and principal components analysis. The model simulates resection operations and local tissue deformations during virtual resectoscope interaction. A mass-spring method is used to model tissue deformation due to surgical tool interaction. Through 3D mesh modification and updating of the nodes of the mesh, the model is able to show in real time, resections and local tissue deformations produced by the user. The anatomical model is designed to assist the surgeon (in conjunction with an optical tracker) to perform Transurethral Resections of the Prostate (TURP) by showing in real time the position of the resectoscope inside the body of the patient and the deformation of the prostate shape during resection.

Improved collision detection algorithm for soft tissue deformable models

The virtual 3D models of human organs in surgery simulation must reproduce the complex viscoelastic deformable behavior of living soft tissue during interaction with virtual surgical tools. Collision detection is a crucial task for modelling and real-time simulation of surgical interactions. Few techniques for collision detection between moving bodies that involve tissue cutting and deformations have been reported. In this paper, we present an improved Quinlan algorithm for collision detection suitable for real-time tissue cutting and deformation simulation. We also present an example of the use of the algorithm in a prostate surgery simulation system.

Dispositivo háptico vibrotáctil inalámbrico para asistencia de actividades motoras

El presente articulo describe la investigacion que condujo al desarrollo de un dispositivo haptico inalambrico, capaz de generar estimulos mecanicos vibrotactiles en diferentes puntos de la piel—y a frecuencias deseadas—por medio de dieciseis actuadores contenidos en un brazalete portatil disenado para cualquier extremidad del cuerpo humano. Este prototipo permite tener control sobre cada actuador usado como punto de estimulacion, accionado de forma independiente por medio de comandos transmitidos inalambricamente hacia un sistema de control autonomo recargable dispuesto en el brazalete. Se realizaron pruebas de usabilidad, con respecto a la percepcion tactil, que comprobaron el correcto funcionamiento del dispositivo. En perspectiva, el desarrollo, luego de una variedad de pruebas de validacion con una amplia muestra de pacientes con y sin neuropatias, tiene como fin la creacion de una base de datos para ser usada como valores consigna frente a estos pacientes—esperando que el sistema se use tambien en pacientes con deficit de movimiento— y empleando la percepcion tactil como estimulante psicomotor en la ejecucion de actividades motoras.

Simulador de reparación de aneurismas cerebrales para entrenamiento médico

El desarrollo de sistemas de simulacion de procedimientos quirurgicos se ha convertido desde hace algunos anos en un tema de investigacion para diversas areas que incluyen a la computacion, la robotica y la medicina, pues suponen una alternativa novedosa para la adquisicion de habilidades medicas, planeacion, guia y control postoperatorio; al mismo tiempo que representan retos significativos en terminos de su diseno, implementacion y validacion. En este trabajo se presentan las experiencias y metodologias aplicadas al desarrollo de simuladores computarizados para entrenamiento virtual en la Unidad de Investigacion y Desarrollo Tecnologico (UIDT) en el Hospital General de Mexico (HGM) “Dr. Eduardo Liceaga”, de la Universidad Nacional Autonoma de Mexico (UNAM). Como caso de estudio, se ejemplifica el desarrollo de un simulador para la reparacion de aneurismas cerebrales, el cual ha involucrado la investigacion en metodos de simulacion computacional, visualizacion, sensaciones tactiles e interaccion humano-computadora.

Virtual Simulation of Brain Sylvian Fissure Exploration and Aneurysm Clipping with Haptic Feedback for Neurosurgical Training

The development of simulation systems from surgical procedures has been a research topic in several areas in medicine and engineer applications because it supposes a novel alternative for medical skills acquisition, surgical planning, guide during surgery and postoperative control. At the same time, simulation systems represent significant challenges, regarding conceptual design, mathematical, numeric and computational modelling, and finally the validation of the system. In this paper, we present the advances and methodologies applied for the development of a virtual reality system for medical training in neurosurgery. As the case of study, we present the simulation of an aneurysm clipping procedure in two of the main stages: brain Sylvian fissure exploration and aneurysm clipping.

Computer vision system for evaluating the Schober’s test

The study of diseases that affect the mobility of patients requires precise measurements that provide information that allows the specialist to classify the progress and severity of the disease. In the case of the evaluation of ankylosing spondylitis the Schober’s test or modified Schober’s test is commonly used to evaluate the subject. The test is based on a set of physical exercises providing an index of mobility; some of the tests are the lower back under flexion, neck mobility, Occiput-to-Wall measurement, and leg-split capacity. The obtained indexes are used to evaluate the current condition of the subject. Traditionally these measurements are obtained manually by the specialist and there are questions related to the correct execution of each activity, subject by subject. In order to provide a more accurate method that can be used to assess the full range of movements, a tridimensional tracking system based on the Kinect v2 sensor is proposed and evaluated in this work.

Mechatronics Interface for Computer Assisted Prostate Surgery Training

In this work is presented the development of a mechatronics device to simulate the interaction of the surgeon with the surgical instrument (resectoscope) used during a Transurethral Resection of the Prostate (TURP). Our mechatronics interface is part of a computer assisted system for training in TURP, which is based on a 3D graphics model of the prostate which can be deformed and resected interactively by the user. The mechatronics interface, is the device that the urology residents will manipulate to simulate the movements performed during surgery. Our current prototype has five degrees of freedom, which are enough to have a realistic simulation of the surgery movements. Two of these degrees of freedom are linear, to determinate the linear displacement of the resecting loop and the other three are rotational to determinate three directions and amounts of rotation.