1,159 research outputs found

    Fast and adaptive fractal tree-based path planning for programmable bevel tip steerable needles

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    漏 2016 IEEE. Steerable needles are a promising technology for minimally invasive surgery, as they can provide access to difficult to reach locations while avoiding delicate anatomical regions. However, due to the unpredictable tissue deformation associated with needle insertion and the complexity of many surgical scenarios, a real-time path planning algorithm with high update frequency would be advantageous. Real-time path planning for nonholonomic systems is commonly used in a broad variety of fields, ranging from aerospace to submarine navigation. In this letter, we propose to take advantage of the architecture of graphics processing units (GPUs) to apply fractal theory and thus parallelize real-time path planning computation. This novel approach, termed adaptive fractal trees (AFT), allows for the creation of a database of paths covering the entire domain, which are dense, invariant, procedurally produced, adaptable in size, and present a recursive structure. The generated cache of paths can in turn be analyzed in parallel to determine the most suitable path in a fraction of a second. The ability to cope with nonholonomic constraints, as well as constraints in the space of states of any complexity or number, is intrinsic to the AFT approach, rendering it highly versatile. Three-dimensional (3-D) simulations applied to needle steering in neurosurgery show that our approach can successfully compute paths in real-time, enabling complex brain navigation

    La Transformaci贸 d'una economia insular. El cas de Menorca : 1600-1920

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    Energy shaping control of soft continuum manipulators with in-plane disturbances

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    Soft continuum manipulators offer levels of compliance and inherent safety that can render thema superior alternative to conventional rigid robotsfor a variety of tasks, such as medical interventions or human-robot interaction. However, the ability of soft continuum manipulators to compensate external disturbances need to be further enhanced to meet the stringent requirements of many practical applications.In this paper, we investigate the control problem forsoft continuum manipulators that consist of one inextensible segmentof constant section, which bends under the effect of the internal pressure and is subject to unknown disturbances acting in the plane of bending. A rigid-link model of the manipulatorwith a single input pressureis employed for control purposes and an energy-shaping approach isproposedto derive thecontrol law. A method for the adaptive estimation of disturbances is detailed and a disturbance compensation strategy is proposed.Finally, the effectiveness of the controlleris demonstrated with simulations and with experiments on an inextensible soft continuum manipulator that employs pneumatic actuation

    Langerhans麓cell histiocytosis

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    La histiocitosis de c茅lulas de Langerhans (HCL), anteriormente conocida como histiocitosis X, es una enfermedad poco frecuente caracterizada por la acumulaci贸n y proliferaci贸n de histiocitos, eosin贸filos y c茅lulas de Langerhans, con inclusi贸n de gr谩nulos de Birbeck detectables por microscopia electr贸nica, afectando 贸rganos y sistemas de forma aislada o m煤ltiple. El diagn贸stico se realiza mediante biopsia de la lesi贸n y la confirmaci贸n de la presencia de CD1a y/o CD207 en la misma. Las distintas formas de presentaci贸n producen distinto enfoque terap茅utico y pron贸stico, desde formas benignas, autolimitadas, con resoluci贸n espont谩nea hasta otras de curso t贸rpido o maligno.Langerhans鈥 cell histiocytosis (LCH), previously known as histiocytosis X, is a rare disease. It is characterized by the accumulation and proliferation of histiocytes, eosinophils and Langerhans鈥 cells with Birbeck granules detected by electron microscopy. It involves single organs or systems or can present as a multisystem disease. The diagnosis is made by biopsy of the lesion and confirming the presence of CD1a and / or CD207 on it. The clinical presentation may vary widely, ranging from benign self-limiting types with spontaneous regression to slowly progressive malignant disease.Fil: Casanovas, A.. Gobierno de la Ciudad de Buenos Aires. Hospital General de Ni帽os Pedro Elizalde (ex Casa Cuna); ArgentinaFil: Elena, G.. Gobierno de la Ciudad de Buenos Aires. Hospital General de Ni帽os Pedro Elizalde (ex Casa Cuna); ArgentinaFil: Rosso, Diego. Gobierno de la Ciudad de Buenos Aires. Hospital General de Ni帽os Pedro Elizalde (ex Casa Cuna); Argentina. Consejo Nacional de Investigaciones Cient铆ficas y T茅cnicas; Argentin

    Kinematics of continuum robots with constant curvature bending and extension capabilities

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    Continuum robots are becoming increasingly popular due to the capabilities they offer, especially when operating in cluttered environments, where their dexterity, maneuverability, and compliance represent a significant advantage. The subset of continuum robots that also belong to the soft robots category has seen rapid development in recent years, showing great promise. However, despite the significant attention received by these devices, various aspects of their kinematics remain unresolved, limiting their adoption and obscuring their potential. In this paper, the kinematics of continuum robots with the ability to bend and extend are studied, and analytical, closed-form solutions to both the direct and inverse kinematics are presented. The results obtained expose the redundancies of these devices, which are subsequently explored. The solution to the inverse kinematics derived here is shown to provide an analytical, closed-form expression describing the curve associated with these redundancies, which is also presented and analyzed. A condition on the reachable end-effector poses for robots with six actuation degrees-of-freedom (DOFs) is then distilled. The kinematics of robot layouts with over six actuation DOFs are subsequently considered. Finally, simulated results of the inverse kinematics are provided, verifying the study

    Development of a new, wireless acquisition system for EMATs compatible with the robotics operating system

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    The deployment of transducers to perform in situ inspections of industrial components can be complicated, and in many cases is still performed manually by a team of operators, which involves significant costs and can be dangerous. Robots capable of deploying probes in difficult to access locations are becoming available. Electromagnetic acoustic transducers (EMAT) are well suited to be used with robots since they are noncontact transducers that do not require a coupling medium, and can easily perform scans. However, existing acquisition systems for EMATs are generally not suitable to be directly mounted on robots. In this paper, a new wireless acquisition system for EMATs is presented. The system is standalone, it transmits the inspection data over WiFi, and is compatible with the robotics operating system (ROS). In addition, it is designed to be modular, small and lightweight so that it can be easily mounted on robots. The system design in terms of hardware and software is described in this paper. The resulting performance of the system is also reported

    La cinerradiograf铆a en Oftalmolog铆a

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