Browsing by Author "Serna Maldonado, Rafael Daniel"
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Item A novel and low-complexity peak detection algorithm for heart rate estimation from low-amplitude photoplethysmographic (PPG) signals(Taylor and Francis Ltd, 2019-03) Argüello Prada, Erick Javier; Serna Maldonado, Rafael DanielLow-amplitude PPG signals are more affected by noise contamination and other undesirable effects because the signal strength is comparable to noise power. Although several authors claim that decreases in the amplitude of the PPG wave should be addressed from signal acquisition and conditioning stages such decreases can also be associated with changes in the patient condition. In that instance, it is important to ensure continuous and reliable HR monitoring which, in turn, depends on how robust is the peak detection method. Numerous efforts have been made to develop algorithms for accurate PPG peak detection under high motion artefact conditions. However, little has been done regarding peak detection in low-amplitude PPG signals. In an attempt to address this issue, a novel and simple peak detection algorithm for PPG signals was proposed. Results show that our method could be a good contribution for robust strategies that can dynamically adapt their peak detection method to circumstances in which a decrease in the amplitude of the PPG signal is expected. Still, more extensive testing under a wide range of conditions (e.g. intensive physical exercise) is needed to perform a rigorous validation.Item Estimación de parámetros en la terapia de hipertermia por radiofrecuencia para el tratamiento del cáncer(Universidad Santiago de Cali, 2019) Serna Maldonado, Rafael Daniel; López Pérez, Jorge Iván; Bermeo Varón, Leonardo AntonioRadiofrequency (RF) hyperthermia is a therapy that takes advantage of the penetration qualities of electromagnetic waves to induce heating in tissues; this therapy is combined with radiotherapy for cancer treatment and chemotherapy that increases to effectiveness of treatment. The mechanism of action of this therapy is the increase of temperature in the tumor, in order to achieve apoptosis of the cell that has an excessive growth and thus generate immediate cell death. This treatment, despite demonstrating its effectiveness, has many limitations such as the low penetrability of the wave, which suggests that the treatments are usually for superficial or shallow tumor tissues. In addition, the concentration of heating at a specific point is another major problem, since when it is induced it is not limited only to tumor tissue, but it affects healthy tissues and to this is added the fact that not all patients present with same physical characteristics in the tissues, which makes the therapy different in the treatment implementation. This paper deals with the estimates of the parameters in radiofrequency hyperthermia therapy, with simulated experimental data and numerical solution of the system, by means of the Gauss-Newton and Levenberg-Marquardt (LM) algorithms, to specify the treatment depending of patient. The results indicate that it is possible to estimate a parameter, obtaining excellent results with the LM optimization algorithm that allow to make a planning for therapy in a specified patient and least possible damage to normal and healthy tissue.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.