1,721,457 research outputs found
EEG-Based BCI System Using Adaptive Features Extraction and Classification Procedures
Full text linkMotor imagery is a common control strategy in EEG-based brain-computer interfaces (BCIs). However, voluntary control of sensorimotor (SMR) rhythms by imagining a movement can be skilful and unintuitive and usually requires a varying amount of user training. To boost the training process, a whole class of BCI systems have been proposed, providing feedback as early as possible while continuously adapting the underlying classifier model. The present work describes a cue-paced, EEG-based BCI system using motor imagery that falls within the category of the previously mentioned ones. Specifically, our adaptive strategy includes a simple scheme based on a common spatial pattern (CSP) method and support vector machine (SVM) classification. The system's efficacy was proved by online testing on 10 healthy participants. In addition, we suggest some features we implemented to improve a system's "flexibility" and "customizability," namely, (i) a flexible training session, (ii) an unbalancing in the training conditions, and (iii) the use of adaptive thresholds when giving feedback
Design of a novel force platform for gait analysis: Fem analysis
No full textThe gait analysis of subjects with short and non-uniform gait is difficult using the common
commercial force platforms. The present work consists in the design, based on finite element
method (FEM) analysis, of a force platform of two different dimensions (0:40 0:40 m and
0:80 0:40 m) considering static and dynamic simulation of their behavior. The aim of this
project is to improve, with a simple, low cost and flexible structure, the instrumentation
available for the gait analysis of children, neurologic patients and in general the most common
clinical cases. The applicability of gait analysis to children, neurologic patients ECC can be
improved by the flexibility of force platforms without losing the performance provided by
traditional force platforms (e.g., for postural analysis)
Automatic generation of accurate subject-specific bone finite element models to be used in clinical studies
No full textMost of the finite element models of bones used in orthopaedic biomechanics research are based on generic anatomies. However, in many cases it would be useful to generate from CT data a separate finite element model for each subject of a study group. In a recent study a hexahedral mesh generator based on a grid projection algorithm was found very effective in terms of accuracy and automation. However, so far the use of this method has been documented only on data collected in vitro and only for long bones. The present study was aimed at verifying if this method represents a procedure for the generation of finite element models of human bones from data collected in vivo, robust, accurate, automatic and general enough to be used in clinical studies. Robustness, automation and numerical accuracy of the proposed method were assessed on five femoral CT data sets of patients affected by various pathologies. The generality of the method was verified by processing a femur, an ileum, a phalanx, a proximal femur reconstruction, and the micro-CT of a small sample of spongy bone. The method was found robust enough to cope with the variability of the five femurs, producing meshes with a numerical accuracy and a computational weight comparable to those found in vitro. Even when the method was used to process the other bones the levels of mesh conditioning remained within acceptable limits. Thus, it may be concluded that the method presents a generality sufficient to cope with almost any orthopaedic application
Anatomical calibration for wearable motion capture systems: Video calibrated anatomical system technique
No full textInertial sensors are becoming widely used for the assessment of human movement in both clinical and research applications, thanks to their usability out of the laboratory. This work aims to propose a method for calibrating anatomical landmark position in the wearable sensor reference frame with an ease to use, portable and low cost device. An off-the-shelf camera, a stick and a pattern, attached to the inertial sensor, compose the device. The proposed technique is referred to as video Calibrated Anatomical System Technique (vCAST). The absolute orientation of a synthetic femur was tracked both using the vCAST together with an inertial sensor and using stereo-photogrammetry as reference. Anatomical landmark calibration showed mean absolute error of 0.6±0.5 mm: these errors are smaller than those affecting the in-vivo identification of anatomical landmarks. The roll, pitch and yaw anatomical frame orientations showed root mean square errors close to the accuracy limit of the wearable sensor used (1°), highlighting the reliability of the proposed technique. In conclusion, the present paper proposes and preliminarily verifies the performance of a method (vCAST) for calibrating anatomical landmark position in the wearable sensor reference frame: the technique is low time consuming, highly portable, easy to implement and usable outside laboratory
Micromotions measurement to assess hip stem mechanical stability: an intra-operative device
No full textNumerical model to predict the long-term mechanical stability of cementless orthopaedic implants
No full textThe objective of this research was to develop a purely biomechanical model, intended to predict the long-term secondary stability of the implant starting from the biomechanical stability immediately after the operation. A continuous rule-based adaptation scheme was formulated as a dynamic system, and the work verified if such a model produced unique and clinically meaningful solutions. It also investigated whether this continuous model provided results comparable with those of a simpler, discrete-states model used in a previous study. The proposed model showed stable convergence behaviour with all investigated initial conditions, with oscillatory behaviour limited to the first steps of the simulation. The results obtained with the wide range of initial conditions support the hypothesis of the existence and uniqueness of the solution for all initial conditions. The differences between the continuous model and the simpler and more efficient finite-states model were found to be extremely modest (less than 4% over the predicted bonded area). Because of these minimal differences, the use of the much faster finite-states model is recommended to investigate asymptotic conditions, and the continuous model described should be used to investigate the evolution over time of the adaptive process
Force Sensor for Instrumented Patellar Prostheses: Development and Characterization
Full text linkThe development of an instrumented patellar prosthesis, able to measure the contact forces at the patellofemoral joint, can significantly aid in investigating the causes of total knee arthroplasty failures due to patellar complications. This study focuses on developing and validating an instrumented patellar prosthesis to measure contact forces in the patellofemoral joint. A piezoresistive force sensor was characterized and integrated into a conditioning circuit, with the aim of its implementation in the prosthesis. To measure medial and lateral forces independently, the sensors were trimmed in half. Compression tests (up to 2000 N) assessed sensor performance in terms of linearity (R2 = 0.998 intact vs. 0.989 trimmed), repeatability (0.9% intact vs. 0.8% trimmed), and accuracy (1.7% intact vs. 2.3% trimmed) for forces up to 250 N. Higher force levels resulted in increased errors, but at a rate still comparable to that of existing sensors in the literature. Key considerations for the design of the instrumented prosthesis, such as minimizing point and shear loads, were identified. A prototype prosthesis capable of housing the sensor was proposed. The integrated system shows potential for improving the understanding of Total knee arthroplasty (TKA) failures through in vitro studies and could serve as an intraoperative tool for the evaluation of bone resections
Tecnologie indossabili per il monitoraggio e la prevenzione delle cadute nell'anziano
No full textSe si prende in considerazione uno dei cosiddetti giganti geriatrici, appare evidente come le cadute costituiscano un pesante onere economico e sociale, determinando una significativa riduzione della qualità di vita nella popolazione anziana e/o patologica. Nel solo 2009, le cadute hanno determinato costi che variano tra lo 0,85 e lo 1,5 per cento delle spese sanitarie totali negli Stati Uniti, Australia, UE e Regno Unito (Heinrich et al., 2009). Le cadute hanno anche un impatto notevole sulle condizioni di salute generali di uno stato, dato che lo 81-98% delle fratture sono causate da cadute (Tinetti, 2003), e queste sono la principale causa di accessi al pronto soccorso in USA (Fuller, 2000).
Il rischio di una caduta aumenta con l'età (Mathers e Weiss, 1998); le cadute rappresentano l'eziologia primaria di morte accidentale in soggetti con più di 65 anni, e anche il tasso di mortalità associato aumenta notevolmente con l'età, con picchi pari al 70% delle morti accidentali nelle persone di 75 anni di età (Fuller, 2000). I principali costi associati tendono quindi a verificarsi in gruppi di età più avanzata e a seguito di fratture (si veda il capitolo di Luca Cristofolini in questo volume), un problema che si aggrava ulteriormente con l’invecchiamento della popolazione (Hamacher et al., 2011).
Risulta quindi chiaro l’interesse nell’individuazione di metodi efficaci, che consentano di identificare i soggetti a rischio e di mettere a punto interventi clinici/riabilitativi capaci di ridurre tale rischio. Purtroppo, però, questo risulta tutt’altro che semplice dato che, in base alle valutazioni epidemiologiche, il rischio di caduta ha una natura multifattoriale e può essere il risultato di quadri clinici e condizioni ambientali molto diversi da un soggetto all’altro. Sia la stabilità posturale che quella motoria sono il risultato dell’azione concorrente di diverse risorse funzionali
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