Ieee Transactions on Evolutionary Computation, 2014
ABSTRACT Reliable knowledge of in vivo joint kinematics is fundamental in clinical medicine. Fluo... more ABSTRACT Reliable knowledge of in vivo joint kinematics is fundamental in clinical medicine. Fluoroscopic motion tracking theoretically permits a millimeter/degree level of accuracy in 3D joint motion analysis, but the reliability of the local optimization algorithm (Levenberg-Marquardt, LMA), typically used for the pose estimation, is highly operator dependent. A new Memetic Algorithm (MA), hybridizing global evolution and a local search metaphor for learning, is proposed to automate the analysis and improve its reliability and robustness. The performance of MA was assessed for in silico and in vivo elbow kinematics, with and without user supervision. The best learning strategy between Lamarckian and Baldwinian evolution was identified. MA’s accuracy and repeatability was quantified and compared with LMA’s. The algorithm performed best using a partial Lamarckian learning strategy. The geometric symmetry of analysed bony segments influenced the accuracy, whereas the absolute bone pose with respect to the projection geometry affected the repeatability. In contrast to LMA, MA provided robust, repeatable, and operator independent pose estimations, even for in vivo analyses. The pose can be automatically estimated with errors lower than 1 mm and 1 deg for all the pose parameters except the depth position, if the investigated motion task avoids symmetric bony projection silhouettes.
La presente opera può essere liberamente consultata ed utilizzata, può essere riprodotta in via p... more La presente opera può essere liberamente consultata ed utilizzata, può essere riprodotta in via permanente in formato digitale (cd salvataggio) e può esserne effettuata la stampa su carta con apparecchiature private (senza ricorso a terzi operatori professionali), per fini ...
Inertial sensors are becoming widely used for the assessment of human movement in both clinical a... more Inertial 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.
Journal of Mechanics in Medicine and Biology, 2015
ABSTRACT The gait analysis of subjects with short and non-uniform gait is difficult using the com... more ABSTRACT The 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).
Twenty infants (age 10-16 month) were analyzed using inertial sensors over a 6-month period after... more Twenty infants (age 10-16 month) were analyzed using inertial sensors over a 6-month period after the onset of independent walking. Changes in gait temporal parameters, coordination and gait strategies were evaluated. Gait temporal parameters showed a developmental shift at 2 months of walking experience: after this period, a change in the developmental trend was present in most of the analyzed parameters. Cadence results showed that the increased velocity is more due to an increase in step length than to an increase in cadence, after the first two months of independent walking. Different gait strategies were identified during the first month of independent gait based on collected data; after one month, characteristics of the pendulum mechanism were present in each examined toddler.
Journal of neuroengineering and rehabilitation, 2014
Quantifying gait stability is a topic of high relevance and a number of possible measures have be... more Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The problem in validating these methods is the necessity to identify a-priori unstable individuals. Since proposed methods do not make any assumption on the characteristics of the subjects, the aim of the present study was to test the performance of gait stability measures on individuals whose gait is a-priori assumed unstable: toddlers at the onset of independent walking. Ten toddlers, ten adults and ten elderly subjects were included in the study. Data from toddlers were acquired longitudinally over a 6-month period to test if the methods detected the increase in gait stability with experience, and if they could differentiate between toddlers and young adults. Data from elderly subjects were expected to indicate a stability value in between the other two groups. Accelerations and angular velocities of the trunk and of the leg were measured using two tri-axial inertial sens...
ABSTRACT Twenty infants (age 10-16 month) were analysed using inertial sensors over a 6-month per... more ABSTRACT Twenty infants (age 10-16 month) were analysed using inertial sensors over a 6-month period after the onset of independent walking. Changes in gait temporal parameters, coordination and gait strategies were evaluated. Gait temporal parameters showed a developmental shift at 2 months of walking experience: after this period, a change in the developmental trend was present in most of the analyzed parameters. Cadence results showed that the increased velocity is more due to an increase in step length than to an increase in cadence, after the first two months of independent walking. Different gait strategies were identified during the first month of independent gait based on collected data; after one month, characteristics of the pendulum mechanism were present in each examined toddler.
Ieee Transactions on Evolutionary Computation, 2014
ABSTRACT Reliable knowledge of in vivo joint kinematics is fundamental in clinical medicine. Fluo... more ABSTRACT Reliable knowledge of in vivo joint kinematics is fundamental in clinical medicine. Fluoroscopic motion tracking theoretically permits a millimeter/degree level of accuracy in 3D joint motion analysis, but the reliability of the local optimization algorithm (Levenberg-Marquardt, LMA), typically used for the pose estimation, is highly operator dependent. A new Memetic Algorithm (MA), hybridizing global evolution and a local search metaphor for learning, is proposed to automate the analysis and improve its reliability and robustness. The performance of MA was assessed for in silico and in vivo elbow kinematics, with and without user supervision. The best learning strategy between Lamarckian and Baldwinian evolution was identified. MA’s accuracy and repeatability was quantified and compared with LMA’s. The algorithm performed best using a partial Lamarckian learning strategy. The geometric symmetry of analysed bony segments influenced the accuracy, whereas the absolute bone pose with respect to the projection geometry affected the repeatability. In contrast to LMA, MA provided robust, repeatable, and operator independent pose estimations, even for in vivo analyses. The pose can be automatically estimated with errors lower than 1 mm and 1 deg for all the pose parameters except the depth position, if the investigated motion task avoids symmetric bony projection silhouettes.
La presente opera può essere liberamente consultata ed utilizzata, può essere riprodotta in via p... more La presente opera può essere liberamente consultata ed utilizzata, può essere riprodotta in via permanente in formato digitale (cd salvataggio) e può esserne effettuata la stampa su carta con apparecchiature private (senza ricorso a terzi operatori professionali), per fini ...
Inertial sensors are becoming widely used for the assessment of human movement in both clinical a... more Inertial 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.
Journal of Mechanics in Medicine and Biology, 2015
ABSTRACT The gait analysis of subjects with short and non-uniform gait is difficult using the com... more ABSTRACT The 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).
Twenty infants (age 10-16 month) were analyzed using inertial sensors over a 6-month period after... more Twenty infants (age 10-16 month) were analyzed using inertial sensors over a 6-month period after the onset of independent walking. Changes in gait temporal parameters, coordination and gait strategies were evaluated. Gait temporal parameters showed a developmental shift at 2 months of walking experience: after this period, a change in the developmental trend was present in most of the analyzed parameters. Cadence results showed that the increased velocity is more due to an increase in step length than to an increase in cadence, after the first two months of independent walking. Different gait strategies were identified during the first month of independent gait based on collected data; after one month, characteristics of the pendulum mechanism were present in each examined toddler.
Journal of neuroengineering and rehabilitation, 2014
Quantifying gait stability is a topic of high relevance and a number of possible measures have be... more Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The problem in validating these methods is the necessity to identify a-priori unstable individuals. Since proposed methods do not make any assumption on the characteristics of the subjects, the aim of the present study was to test the performance of gait stability measures on individuals whose gait is a-priori assumed unstable: toddlers at the onset of independent walking. Ten toddlers, ten adults and ten elderly subjects were included in the study. Data from toddlers were acquired longitudinally over a 6-month period to test if the methods detected the increase in gait stability with experience, and if they could differentiate between toddlers and young adults. Data from elderly subjects were expected to indicate a stability value in between the other two groups. Accelerations and angular velocities of the trunk and of the leg were measured using two tri-axial inertial sens...
ABSTRACT Twenty infants (age 10-16 month) were analysed using inertial sensors over a 6-month per... more ABSTRACT Twenty infants (age 10-16 month) were analysed using inertial sensors over a 6-month period after the onset of independent walking. Changes in gait temporal parameters, coordination and gait strategies were evaluated. Gait temporal parameters showed a developmental shift at 2 months of walking experience: after this period, a change in the developmental trend was present in most of the analyzed parameters. Cadence results showed that the increased velocity is more due to an increase in step length than to an increase in cadence, after the first two months of independent walking. Different gait strategies were identified during the first month of independent gait based on collected data; after one month, characteristics of the pendulum mechanism were present in each examined toddler.
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Papers by Rita Stagni