Conception d'un robot positionneur d'aiguille pour les interventions percutanées au niveau du foie, guidées par IRM

Dans la dernière décennie, la robotique souple a connu un gain de popularité considérable. Elle est, de façon inhérente, sécuritaire pour les humains et l’environnement qui l’entourent. Grâce à sa faible rigidité, la robotique souple est idéale pour manipuler des objets fragiles et elle est en mesure de s’adapter à son environnement. Les caractéristiques uniques de la robotique souple font de cette technologie un tremplin vers la conception d’appareils médicaux novateurs, plus particulièrement pour des outils permettant le positionnement d’aiguilles dans le but de faire des interventions percutanées, notamment au niveau du foie. Toutefois, la souplesse de cette technologie induit, du même coup, quelques désagréments. Elle procure un comportement sécuritaire, mais entraîne aussi un manque de rigidité limitant les applications de la robotique souple. Sans une rigidité minimale, il est impossible d’accomplir des opérations repérables et précises. La robotique souple a en fait un compromis majeur entre la capacité de chargement et la plage d’utilisation. Pour utiliser cette technologie dans le domaine médical, il est primordial d’ajouter un système permettant de moduler la rigidité du système pour inhiber ce compromis. Couplée avec un système de freinage granulaire, la robotique souple semble comporter l’ensemble des caractéristiques permettant d’accomplir des interventions au foie. Cette étude tend à démontrer que couplée à un système modulant la rigidité, la robotique souple peut être utilisée pour accomplir des opérations d’une façon précise et repérable, tout en demeurant sécuritaire. Le positionneur d’aiguilles développé est 100 % compatible avec l’Imagerie à Résonance Magnétique (IRM). La plage d’insertion du système permet de rejoindre l’entièreté du foie (1500 cm³), tout en maintenant une rigidité suffisante (3 N/mm) et en étant aussi précis que l’outil d’imagerie utilisée (1 mm). L’approche hybride consistant à développer un système activé de façon souple couplée à un module régulant sa rigidité permet d’obtenir à la fois les avantages d’une robotique compliante (souple) et conventionnelle (dure)

Development of a Compact Piezoworm Actuator For Mr Guided Medical Procedures

In this research, a novel piezoelectric actuator was developed to operate safely inside the magnetic resonance imaging (MRI) machine. The actuator based on novel design that generates linear and rotary motion simultaneously for higher needle insertion accuracy. One of the research main objectives is to aid in the selection of suitable materials for actuators used in this challenging environment. Usually only nonmagnetic materials are used in this extremely high magnetic environment. These materials are classified as MRI compatible materials and are selected to avoid hazardous conditions and image quality degradation. But unfortunately many inert materials to the magnetic field do not possess desirable mechanical properties in terms of hardness, stiffness and strength and much of the available data for MRI compatible materials are scattered throughout the literature and often too device specific . Furthermore, the fact that significant heating is experienced by some of these devices due to the scanner’s variable magnetic fields makes it difficult to draw general conclusions to support the choice of suitable material and typically these choices are based on a trial-and-error with extensive time required for prototype development and MRI testing of such devices. This research provides a quantitative comparison of several engineering materials in the MRI environment and comparison to theoretical behavior which should aid designers/engineers to estimate the MRI compatible material performance before the expensive step of construction and testing. This work focuses specifically on the effects in the MRI due to the material susceptibility, namely forces, torques, image artifacts and induced heating

Level Set Methods for MRE Image Processing and Analysis

Ph.DDOCTOR OF PHILOSOPH

Principles of Small-Scale Hydraulic Systems for Human Assistive Machines

University of Minnesota Ph.D. dissertation. March 2017. Major: Mechanical Engineering. Advisor: William Durfee. 1 computer file (PDF); xiii, 288 pages.The high power and force density of hydraulic actuators, along with the ability to distribute system weight through the separation of the power supply and actuators makes hydraulic technology ideal for use in human assistive machines. However, hydraulic systems often operate inefficiently due to throttling losses in the control valves and have increased viscous losses in small-scale applications as bore size is decreased. The objective of this research is to address the limitations of small-scale hydraulics using validated modeling techniques to optimize performance and minimize system weight. This research compares and contrasts the use of different hydraulic technology as well as develops detailed models of small-scale hydraulic components. These models are used to construct a software tool that optimizes the design of a hydraulic system using specified input requirements of actuation, conduit lengths, operating pressure, and runtime. A system-level energetics analysis provides estimates of efficiencies and weights, while a heat transfer analysis estimates the working fluid and component surface temperatures. In addition, the dynamic performance of different small-scale pump and valve controlled hydraulic systems are simulated to compare the cycle efficiencies, rise times, and flow rate capabilities as a function of duty cycles. The use of an accumulator, unloading valves, variable displacement pumps, and proportional pressure control are explored to improve the efficiency of the system during intermittent operation. In addition a small-scale, digital, high frequency switching valve is designed and simulated to reduce the throttling losses of a traditional proportional control valve. This body of knowledge is used to design, prototype, and performance test two hydraulic powered ankle-foot orthoses. The first orthosis is an untethered system that provides active gait assistance. Hydraulics allows the system to be separated into two parts as the actuator is secured to the ankle, and the portable electrohydraulic power supply is positioned on the lower back. The second orthosis emulates the dynamics of a passive ankle-foot orthosis providing torque assistance to bring the ankle to a neutral position. This device is specifically designed to reduce the time and resources in the clinical prescription of passive ankle-foot orthoses while providing more quantitative metrics

MRI compatible mechatronic devices to aid medical diagnosis and intervention

Imperial Users onl