Currently, exoskeletons can be categorized according to the part of the human body they are focus... more Currently, exoskeletons can be categorized according to the part of the human body they are focused on, their purpose and the type of mechanisms used for their operation. This paper presents the development of an exoskeleton to assist lower-limb motion during human gait and uses the electromyographic (EMG) signals as data acquisition and control system. In addition, the system has an anthropomorphic and adjustable design to serve a larger number of patients and thus make it affordable for a larger sector of the population. In order to verify the suitable operation of the exoskeletal system, experimental tests were carried out with a volunteer and some of the obtained results are presented.
This paper presents the control of a lower-limb exoskeleton in real time, to assist a pathologica... more This paper presents the control of a lower-limb exoskeleton in real time, to assist a pathological gait, taking into account only electromyography (EMG) events and a characteristic angular pattern of a normal gait. The algorithm consists of an impedance control scheme that uses EMG signals to modify the characteristic angular pattern of a normal gait. EMG signals were characterized using the simple square integral (SSI) index and this information was used to identify a characteristic EMG pattern in the semitendinosus and gastrocnemius muscles. Finally, a series of experimental tests were conducted with a volunteer to validate the adequate performance of the system.
The use and analysis of ultrasound images (US) is one of the safest and most accessible ways to m... more The use and analysis of ultrasound images (US) is one of the safest and most accessible ways to monitor and diagnose illness; however, expert knowledge is required for the interpretation of these images. The aim of this project is to propose a practical and low cost alternative for the visualization of anatomical structures in 3D from 2D B mode US images acquired as a video. In particular, this project focused on the 3D reconstruction of the kidney, which is an organ of great importance in keeping the blood clean and maintaining the body’s chemical balance. Our strategy consisted of acquiring the images with portable US equipment and applying digital image processing techniques such as filtering and segmentation in order, to then perform the 3D reconstruction of the anatomical structure of interest.
Abstract Background: Parkinson’s disease (PD) is a chronic and progressive neurodegenerative diso... more Abstract Background: Parkinson’s disease (PD) is a chronic and progressive neurodegenerative disorder characterized by deterioration of the substantia nigra, resulting in a deficiency of dopamine. PD is considered a movement disorder associated with numerous non-motor symptoms related to Autonomic Nervous System failures which can precede the motor ones. Therefore, their awareness could be helpful in the diagnosis of PD at an early stage. Methods: Heart Rate Variability (HRV) is assessed by time and frequency domain indices, and by nonlinear indices based on symbolic dynamics and multiscale symbolic entropy. The features obtained were used to classify between PD patients and control volunteers using a support vector machine. Volunteers performed cardiovascular autonomic reflex tests: active standing, post- hyperventilation and controlled breathing. Results: Temporal and frequency indices showed significantly lower values in PD patients compared to control volunteers. Symbolic dynamics and multiscale symbolic entropy results suggest a decrease in the complexity of the HRV signal in PD patients, in contrast with a more variable pattern of words for control volunteers. During controlled breathing differences between groups were found with most of the indices computed. Additionally, classification process achieves good separability during cardiorespiratory maneuvers (>95% of accuracy) and features based on symbolic dynamics showed high discrimination between groups. Conclusions: The results found in this work suggest that the proposed methodological approach can classify PD patients in an early disease stage from healthy controls and give additional information about the cardiorespiratory system, which could be useful for diagnosis and follow up of PD patients.
This paper presents an application of the Chan-Vese algorithm for a semi-automatic segmentation o... more This paper presents an application of the Chan-Vese algorithm for a semi-automatic segmentation of anatomical structures of interest (lungs and lung tumor) in thorax 4DCT images, as well as its threedimensional reconstruction. Segmentations and reconstructions were performed in 10 CT images, which conform an inspiration-expiration cycle. The maximum displacement of the lung tumor was calculated using the reconstructions of the beginning of inspiration, beginning of expiration, and the voxel size information. The proposed method was able to succesfully segment the studied structures regardless of their size and shape. The threedimensional reconstruction allow us to visualize the dynamics of the structures of interest throughout the respiratory cycle. In the near future, we are expecting to be able to have more evidence of the good performance of the proposed segmentation approach, and to have feedback from a clinical expert, giving the fact that the knowledge of anatomical structures...
Currently, exoskeletons can be categorized according to the part of the human body they are focus... more Currently, exoskeletons can be categorized according to the part of the human body they are focused on, their purpose and the type of mechanisms used for their operation. This paper presents the development of an exoskeleton to assist lower-limb motion during human gait and uses the electromyographic (EMG) signals as data acquisition and control system. In addition, the system has an anthropomorphic and adjustable design to serve a larger number of patients and thus make it affordable for a larger sector of the population. In order to verify the suitable operation of the exoskeletal system, experimental tests were carried out with a volunteer and some of the obtained results are presented.
This paper presents the control of a lower-limb exoskeleton in real time, to assist a pathologica... more This paper presents the control of a lower-limb exoskeleton in real time, to assist a pathological gait, taking into account only electromyography (EMG) events and a characteristic angular pattern of a normal gait. The algorithm consists of an impedance control scheme that uses EMG signals to modify the characteristic angular pattern of a normal gait. EMG signals were characterized using the simple square integral (SSI) index and this information was used to identify a characteristic EMG pattern in the semitendinosus and gastrocnemius muscles. Finally, a series of experimental tests were conducted with a volunteer to validate the adequate performance of the system.
The use and analysis of ultrasound images (US) is one of the safest and most accessible ways to m... more The use and analysis of ultrasound images (US) is one of the safest and most accessible ways to monitor and diagnose illness; however, expert knowledge is required for the interpretation of these images. The aim of this project is to propose a practical and low cost alternative for the visualization of anatomical structures in 3D from 2D B mode US images acquired as a video. In particular, this project focused on the 3D reconstruction of the kidney, which is an organ of great importance in keeping the blood clean and maintaining the body’s chemical balance. Our strategy consisted of acquiring the images with portable US equipment and applying digital image processing techniques such as filtering and segmentation in order, to then perform the 3D reconstruction of the anatomical structure of interest.
Abstract Background: Parkinson’s disease (PD) is a chronic and progressive neurodegenerative diso... more Abstract Background: Parkinson’s disease (PD) is a chronic and progressive neurodegenerative disorder characterized by deterioration of the substantia nigra, resulting in a deficiency of dopamine. PD is considered a movement disorder associated with numerous non-motor symptoms related to Autonomic Nervous System failures which can precede the motor ones. Therefore, their awareness could be helpful in the diagnosis of PD at an early stage. Methods: Heart Rate Variability (HRV) is assessed by time and frequency domain indices, and by nonlinear indices based on symbolic dynamics and multiscale symbolic entropy. The features obtained were used to classify between PD patients and control volunteers using a support vector machine. Volunteers performed cardiovascular autonomic reflex tests: active standing, post- hyperventilation and controlled breathing. Results: Temporal and frequency indices showed significantly lower values in PD patients compared to control volunteers. Symbolic dynamics and multiscale symbolic entropy results suggest a decrease in the complexity of the HRV signal in PD patients, in contrast with a more variable pattern of words for control volunteers. During controlled breathing differences between groups were found with most of the indices computed. Additionally, classification process achieves good separability during cardiorespiratory maneuvers (>95% of accuracy) and features based on symbolic dynamics showed high discrimination between groups. Conclusions: The results found in this work suggest that the proposed methodological approach can classify PD patients in an early disease stage from healthy controls and give additional information about the cardiorespiratory system, which could be useful for diagnosis and follow up of PD patients.
This paper presents an application of the Chan-Vese algorithm for a semi-automatic segmentation o... more This paper presents an application of the Chan-Vese algorithm for a semi-automatic segmentation of anatomical structures of interest (lungs and lung tumor) in thorax 4DCT images, as well as its threedimensional reconstruction. Segmentations and reconstructions were performed in 10 CT images, which conform an inspiration-expiration cycle. The maximum displacement of the lung tumor was calculated using the reconstructions of the beginning of inspiration, beginning of expiration, and the voxel size information. The proposed method was able to succesfully segment the studied structures regardless of their size and shape. The threedimensional reconstruction allow us to visualize the dynamics of the structures of interest throughout the respiratory cycle. In the near future, we are expecting to be able to have more evidence of the good performance of the proposed segmentation approach, and to have feedback from a clinical expert, giving the fact that the knowledge of anatomical structures...
Resumen-La aplicación de una mala técnica durante la práctica de la natación puede incrementar la... more Resumen-La aplicación de una mala técnica durante la práctica de la natación puede incrementar la incidencia de una de las lesiones con mayor concurrencia entre los nadadores, el síndrome del hombro de nadador. En este trabajo se presenta una herramienta de análisis comparativo del movimiento realizado por sujetos de prueba contra una trayectoria patrón, de la brazada del estilo de crol, con el propósito de evaluar cuantitativamente la aplicación correcta de la técnica, para mejorarla o perfeccionarla y disminuir la incidencia de lesiones. Las trayectorias de marcadores, colocados en las articulaciones del brazo, fueron adquiridas mediante un sistema de visión y procesadas utilizando el algoritmo CamShift de la librería OpenCV. Además, se calcularon los valores de distancia simétrica media y distancia máxima para cuantificar la similitud entre las trayectorias a comparar. La herramienta de análisis comparativo fue validada experimentalmente con sujetos nadadores y no nadadores. Palabras clave-Análisis de trayectoria, CamShift, Seguimiento de trayectoria, Síndrome del hombro de nadador.
Resumen— En este trabajo se presenta el desarrollo de un Equipo de ultrasonido (US) portátil en m... more Resumen— En este trabajo se presenta el desarrollo de un Equipo de ultrasonido (US) portátil en modo A para aplicaciones en estudios sobre pequeños animales con fines académicos. Se describe la metodología empleada para el diseño de la instrumentación del equipo, tanto analógica como digital, desde la identificación de los circuitos que componen un equipo de US, hasta el acoplamiento de los mismos. El equipo tiene la capacidad de desplegar la información en una pantalla de cristal líquido de 128x64 pixeles, y de transmitir los datos de los ecos ultrasónicos a una computadora personal a través de un puerto serie. Palabras clave— Ultrasonido portátil, Modo A, Pantalla de cristal líquido. Transmisión serial
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Papers by Aldo Mejia Rodriguez