Browsing by Author "Bermeo Varón, Leonardo A."
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Item Acquisition Protocol and Comparison of Myoelectric Signals of the Muscles Innervated by the Ulnar, Radial and Medial Nerves for a Hand Orthoses(Springer, 2020-03-03) Bermeo Varón, Leonardo A.; Villarejo Mayor, John J.; Arcos, Edgar F.; Quiguanas, Diana M.; Bravo, Andrea A.; Perez Plaza, VanessaThis paper proposes a protocol for obtaining surface myoelectric signals in muscles of the upper limb for characterization of hand movement patterns. To characterize the movement patterns, the magnitude of the signal from each muscle is compared, for eight movements: (i) flexion, (ii) extension, (iii) ulnar and (iv) radial deviation of the hand, (v) metacarpophalangeal flexion, (vi) metacarpophalangeal extension, (vii) opposition and (viii) adduction thumb. Specific points were considered to acquire the signals from muscles innervated by the radial, medial and ulnar nerve, following the recommendations of the SENIAM project, in six intact people, using a myoelectric signal acquisition system. Seven protocols with recommendations for the location of sensors in the muscles were obtained, intended to establish combinations to reduce the number of sensors for future designs of assistive technologies, such as active orthoses. The suitable characteristic patterns for the hand movements studied allows the identification of a reduced set of sensors, considering the same eight movements. In this way, the functionality and rehabilitation processes of hand injuries are improved, facilitating the execution of activities of daily living.Item Comparison of Attenuation Coefficient Estimation in High Intensity Focused Ultrasound Therapy for Cancer Treatment by Levenberg Marquardt and Gauss-Newton Methods(Springer, 2020-03-03) de Los Ríos Cárdenas, Laura; Bermeo Varón, Leonardo A.; de Albuquerque-Pereira, Wagner CoelhoHyperthermia using High-Intensity Focused Ultrasound (HIFU) is an acoustic therapy used in clinical applications to destroy malignant tumors of bone, breast, brain, kidney, pancreas, prostate, rectum and testicle. This technique consists in increase the temperature in the tumor or the specific area, to achieve coagulative necrosis and immediate cell death. Although hyperthermia can cure cancer, it can also cause side effects and even damage healthy cells or tissues. Therefore, for having a successful treatment, it is important to monitor and observe what is the tissue behavior, as well as its changes, before, during and after the procedure. Mathematical models are tools that can be useful to simulate an adequate therapy by differentiating characteristics that will depend on each individual. An attenuation coefficient estimation for a forward model with a rectangular two-dimensional domain is presented, the estimation was made with simulated numerical data and simulated experimental data by Levenberg Marquardt and Gauss-Newton Methods. The results demonstrate that by identifying the attenuation coefficient of each patient. By estimating the attenuation coefficient parameter it is possible to predict the thermal responses of the tissue to be treated and, based on them, to plan an adequate cancer treatment by inducing heat by HIFU.Item Estimation of Electrical Conductivity from Radiofrequency Hyperthermia Therapy for Cancer Treatment by Levenberg Marquardt Method(Springer, 2020-03-03) López Perez, Jorge Iván; Serna Maldonado, Rafael Daniel; Bermeo Varón, Leonardo A.; Castillo García, Javier FerneyIntroduction: The radiofrequency hyperthermia is a technique that by induction of the electromagnetic waves produces the heating in the biological tissues. The increase in body temperature in a range of 40 °C to 46 °C causing heat-induced necrosis, protein inactivity, and inhibition of DNA recovery mechanisms in the cancer cell. The application of this therapy depends on parameters like the frequency and power and physical properties of the tissue, which vary from person to person. One of the important properties is the electrical conductivity of the tissue, which varies depending on the tissue and frequency. In this paper, the electrical conductivity estimation is performed in hyperthermia therapy with different frequencies. Methodology: The estimation process of electrical conductivity is carried out through the Levenberg Marquardt method. The process is performed on simulated experimental data and mathematical model of the system with different frequencies. The geometry used is a copper coil that induces radiofrequency to a domain located in the center of the coil. Results: The estimation of electrical conductivity is obtained to different frequencies from radiofrequency hyperthermia therapy for cancer treatment by the Levenberg Marquardt method. Also, these results allow that by identifying the electrical conductivity of each patient. Conclusions: The estimation of physical properties in the application of cancer treatment is important, in this case with radiofrequency hyperthermia therapy, because it is possible to plan appropriate treatment, due to a better knowledge of the system.Item Estimation of the temperature field in laser-induced hyperthermia experiments with a phantom(Taylor and Francis Ltd, 2018-12-31) Lamien, Bernard; Orlande, Hélcio Rangel Barreto; Bermeo Varón, Leonardo A.; Rodrigo, Leite Queiroga Basto; Enrique Eliçabe, Guillermo; Silva Dos Santos, Dilson; Machado Cotta, RenatoBackground: One of the challenges faced during the hyperthermia treatment of cancer is to monitor the temperature distribution in the region of interest. The main objective of this work was to accurately estimate the transient temperature distribution in the heated region, by using a stochastic heat transfer model and temperature measurements. Methods: Experiments involved the laser heating of a cylindrical phantom, partially loaded with iron oxide nanoparticles. The nanoparticles were manufactured and characterized in this work. The solution of the state estimation problem was obtained with an algorithm of the Particle Filter method, which allowed for simultaneous estimation of state variables and model parameters. Measurements of one single sensor were used for the estimation procedure, which is highly desirable for practical applications in order to avoid patient discomfort. Results: Despite the large uncertainties assumed for the model parameters and for the coupled radiation–conduction model, discrepancies between estimated temperatures and internal measurements were smaller than 0.7 °C. In addition, the estimated fluence rate distribution was physically meaningful. Maximum discrepancies between the prior means and the estimated means were of 2% for thermal conductivity and heat transfer coefficient, 4% for the volumetric heat capacity and 3% for the irradiance. Conclusions: This article demonstrated that the Particle Filter method can be used to accurately predict the temperatures in regions where measurements are not available. The present technique has potential applications in hyperthermia treatments as an observer for active control strategies, as well as to plan personalized heating protocols. © 2018, © 2018 The Author(s). Published with license by Taylor & Francis Group, LLC.Item Mechanical Pain Assessment Through Parameters Derived from Photoplethysmographic (PPG) Signals: A Pilot Study(Springer, 2020-03-03) Ramírez Mena, Andrés David; Bermeo Varón, Leonardo A.; Molano Valencia, Rodolfo; Argüello Prada, Erick JavierBased on the fact that pain modulates the contour of the photoplethysmographic (PPG) signal, several authors have used PPG-derived parameters, like the amplitude of the PPG signal (PPGA) and the variations of the inter-pulse intervals (i.e., the pulse rate variability – PRV), for pain measurement. However, all those studies were limited to use PPG-derived parameters to assess only thermally evoked pain and no recent studies seem to be available to examine whether it is possible to measure the intensity of the pain evoked by mechanical stimulation. The present study aims to analyze whether it is possible to assess the intensity of mechanically induced pain by using PPG-derived parameters. PPG signals were recorded from fifteen healthy subjects during 6 min, and three force stimuli (3, 6 and 9 N) were applied in ascendant order at 90 s intervals to induce three different levels of pain: low, medium and high. The PPGA, the heart rate (HR), and the high-frequency band (0.15 to 0.4 Hz) power of the pulse rate variability (PRV-HF) were computed before and after the initiation of mechanical stimulation and the percentage of change was calculated for each stimulus intensity. Results show that, even though all of the parameters varied considerably in response to painful stimuli, none of them were able to differentiate between three aforementioned levels of mechanical pain. Only HR was capable of differentiating between low and medium pain, as well as between low and high pain.Item Real-time temperature estimation with enhanced spatial resolution during MR-guided hyperthermia therapy(Taylor and Francis Ltd., 2020-04-17) Pacheco, César C.; Barreto Orlande, Hélcio Rangel; Colaço, Marcelo José; Dulikravich, George S.; Bermeo Varón, Leonardo A.; Lamien, BernardIn this article, the temperature of biological tissues is estimated during hyperthermia therapy, while accounting for uncertainties in the bioheat transfer problem and in the available measurements. A state estimation problem is solved with the Steady-State Kalman Filter. The Pennes bioheat transfer model and the PRF-Shift Magnetic Resonance Thermometry are used as evolution and observation models, respectively. Instead of using the direct inversion of the measured data as with the PRF-Shift Magnetic Resonance Thermometry, the state-estimation framework allows for enhancing the spatial resolution of the estimated temperature variation and reducing the related uncertainties. Since the time consuming steps of the Steady-State Kalman Filter can be performed offline, the recursive solution of the state estimation problem is performed with computational times smaller than the simulated physical times. Synthetic measurements are used for the state estimation problem in a region of the human forearm, for radiofrequency and laser-diode heat sources of the hyperthermia therapy.Item Red de telemedicina con tecnologÍa UMTS/GPRS HSPA+ 3G para zonas de difÍcil acceso(International Institute of Informatics and Systemics, IIIS, 2018-03-01) Bermeo Varón, Leonardo A.; Abonia Peña, Oscar E.Una red de telemedicina es un sistema que permite realizar procedimientos médicos y clínicos como exámenes, diagnósticos y supervisión de tratamientos, que utiliza recursos informáticos como servidores, computadores, equipos de procesamiento de imágenes, internet y equipos de transmisión y recepción de información, con la finalidad de mejorar la calidad de los servicios de salud en áreas remotas o rurales. En este artículo se presenta una conexión por medio de la integración de redes de tecnología inalámbrica UMTS/GPRS HSPA+, usando estándares T.120 y H.233, y servicio de internet de tercera generación (3G) de la red de las Empresas Municipales de Cali (EMCALI); el sistema fue implementado en la Red de Salud de Ladera Empresa Social del Estado (E.S.E) en Dagua, zona rural de la ciudad de Cali, Colombia. Se realizó una evaluación para obtener información sobre la evolución de las acciones del sistema y su impacto. Los resultados nos indican que con la combinación de tecnologías obtenemos un buen desempeño del sistema de comunicaciones en cuanto a confiabilidad del servicio de telemedicina y con poca latencia (185 ms) dentro de la cobertura inalámbrica 3G.Item Sensitivity Study in High Intensity Focused Ultrasound Therapy for Cancer(Springer, 2019-09-25) Cárdenas, Laura de Los Ríos; Bermeo Varón, Leonardo A.; Pereira, Wagner Coelho de AlbuquerqueHyperthermia using High Intensity Focused Ultrasound (HIFU) is an acoustic therapy used in clinical applications to destroy malignant tumors of bone, breast, brain, kidney, pancreas, prostate, rectum and testis. This technique consists in raising the temperature in the tumor or specific zone, to achieve coagulative necrosis and immediate cell death. For having a successful treatment, it is important to monitor and observe what is the tissue behavior, as well as its changes, before, during and after the procedure. In this paper, a sensitivity study is presented to determine the suitable parameters that may be estimated using mathematical modeling, thereby simulating an optimal treatment of cancer by heating induced by High Intensity Focused Ultrasound. The sensitivity analysis indicates the conditions under which temperature profiles are sensitive to changes in thermal conductivity and attenuation coefficient. This information provides the basis for estimation of the parameters in different tissues and for prediction of the thermal responses of these tissues.