Reconocimiento de patrones en señales biomédicas para la detección temprana de eventos no fisiológicos
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ItemBayesian inversion approach for ECG denoising(Asociación Argentina de Matemática Aplicada, Computacional e Industrial (ASAMACI), 2019) Bergamini, Maria Lorena ; Liberczuk, Sergio JavierStochastic or Bayesian filtering is an inverse problem in the sense that from given noisy observations we want to estimate hidden state variables knowing models for states evolution and measurement noises. In the present work we propose a Particle Filter method for denoising ECG signals based on Monte Carlo filter techniques estimating the state (filtered signal value) from noisy observations simulated with different SNRs. We use Mc Sharry dynamical model whose solution trajectories reproduce realistic ECG waves. The improvement in the denoised signal is higher when the SNR in the input signal is lower. Particle Filter method allows any noise distribution to be considered. This property is very interesting for physiological signal processing, where the noise is often complex and non Gaussian.
ItemHeart beat parametric modeling based on Monte Carlo fitting techniques(Sociedad Argentina de Bioingeniería, 2019-3-28) Liberczuk, Sergio Javier ; Bergamini, María Lorena ; Arini, PedroSynthesis of electrocardiogram (ECG) signals is closely linked to the modeling process since precise knowledge of the parameters of the heartbeat to be modeled is required. The knowledge of these parameters is achieved through methods of adjusting curves between simulated beats and real beats. These traditional optimization methods, such as nonlinear least squares or similar, suffer from the drawback of falling at local minima especially when the initial conditions are not given in an accurate fashion. In the present work, we have designed a novel method robust to deviations in the initial conditions based on Monte Carlo techniques derived from the ideas of the Particle Filtering. Our method allows to adjust the heart beat and to determine the parameters of a model already known in the literature that consists of the sum of five Gaussian curves. The method fits with errors very similar to the traditional method when the initial conditions are good, but better results are obtained in terms of squared error when the initial conditions are sufficiently degraded. Validation was carried out with real physiological and pathological ECG records from international databases.