2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006
The purpose of this work is to characterize the heart rate variability (HRV) of patients affected... more The purpose of this work is to characterize the heart rate variability (HRV) of patients affected by congestive heart failure (CHF) and to find out the main difference between this pathological condition and the physiological state. Parameters adopted in this work are: the detrended fluctuation analysis (DFA) and the Higuchi exponent to assess long correlations and self-similarity; the regularity estimators, approximate entropy (ApEn) and sample entropy (SampEn) and the multiscale entropy (MSE). Furthermore we proposed a new regularity index, the Gaussian entropy (GaussEn) which is a modification of the previous ApEn and SampEn. The results show the proposed parameters do an effective separation of physiological and pathological subject conditions. These results are part of a study evaluating the nonlinear index prognostic value toward cardiac death.
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286)
The paper presents a wavelet packets (WP) decomposition method for the post-processing of chemica... more The paper presents a wavelet packets (WP) decomposition method for the post-processing of chemical-shift 1H-MRS data and for an automatic computation of metabolic maps within anatomical brain regions. WP decomposition is used to analyze the recorded FID signals and to isolate the different metabolite contributions in different frequency bands. In each sub-band LPSDV method has been applied to compute the peak parameters. The main metabolic component are then automatically classified by using peak information such as center frequency and damping factor. The estimated peak amplitudes are then used to construct maps of metabolic concentrations in the analyzed region
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, 2011
The Amplitude of Dominant T-Wave Alternans (ADTWA) is a recently introduced index which quantifie... more The Amplitude of Dominant T-Wave Alternans (ADTWA) is a recently introduced index which quantifies the presence of microvolt T Wave Alternans (TWA) on surface ECG recordings. In this paper we investigate the reliability of ADTWA and its robustness against broadband noise. At this regard, we generated synthetic 12-leads ECG recordings through a forward electrophysiological model and we added TWA, at different extent, by modulating the variation of the repolarization times of transmembrane action potentials across even and odd beats. Using a stochastic model, we derived an analytical relationship between the repolarization variation injected into the model and TWA at the surface, thus offering a strategy to evaluate lead sensitivity. In terms of robustness, the results of the simulations show that ADTWA correctly measured the amplitude of synthetic TWA with an average error of 3.3% ± 5.8% in absence of noise. When a 100 μV peak-to-peak broadband noise is present, its effects on estimation errors were kept limited by singular value decomposition on which ADTWA builds.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2006
The long term goal of our research is to develop a tool for recognizing human emotions during e-l... more The long term goal of our research is to develop a tool for recognizing human emotions during e-learning processes. This could be accomplished by combining quantitative indexes extracted from non-invasive recordings of four physiological signals: namely skin conductance, blood volume pulse, electrocardiogram and electroencephalogram. Wearable, non-invasive sensors, communicating with a PC, were applied to 30 students and data were collected during exposure to three different computer-mediated content stimuli designed to evoke specific emotional states: stress, relaxation and engagement. In this paper we describe both the general emotion evaluation algorithm, and present a preliminary results suggesting that some of the quantitative indexes may be successful in characterizing and distinguishing between the three different emotional states.
A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the h... more A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the heart rate variability (HRV) signal. The power spectrum is calculated from the AR coefficients derived from each single RR interval considered. Time-variant AR coefficients are determined through adaptive parametric identification with a forgetting factor which obtains weighed values on a running temporal window of 50 preceding measurements. Power spectrum density (PSD) is hence obtained at each cardiac cycle, making it possible to follow the dynamics of the spectral parameters on a beat-by-beat basis. These parameters are mainly the LF (low frequency) and the HF (high frequency) powers, and their ratio LF/HF. These together account for the balanced sympatho-vagal control mechanism affecting the heart rate. This method is applied to subjects suffering from transient ischemic attacks. The time variant spectral parameters suggest an early activation of LF component in the HRV power spectrum. It precedes by approximately 1.5-2 min the tachycardia and the ST displacement, generally indicative of the onset of an ischemic episode. The results suggest an arousal of sympathetic system before the acute attack.
Blood pressure variability is the result of a complex interaction between external stimulation an... more Blood pressure variability is the result of a complex interaction between external stimulation and several cardiovascular control mechanisms and is enhanced in all those conditions characterized by an impaired autonomic regulation of circulation. In particular, blood pressure variability is enhanced in hypertension over 24 h and may independently contribute to the cardiovascular complications of this condition. The paper by Mussalo and co-workers in this issue of Clinical Science offers additional information in this field by suggesting that different forms of hypertension are characterized by different patterns of blood pressure variability, and that these differences may reflect variations in the underlying autonomic regulation of the heart and blood vessels.
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society Volume 13: 1991
The monitoring of the patients in the Intensive Care Units requires the identification of several... more The monitoring of the patients in the Intensive Care Units requires the identification of several pressure parameters. This work proposes a monitoring system which evaluates the right and left heart performance using the pressure signal in both the ventricles and in the pulmonary artery. With a Swan-Ganz catheter with supplementary ventricular way we have obtained the continuous right ventricular and
The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
We propose to study the heart rate variability (HRV) time series complexity by computing the Lemp... more We propose to study the heart rate variability (HRV) time series complexity by computing the Lempel Ziv complexity measure. LZ is sensitive to the rate of pattern recurrences in a time series. Analysis considers 24 h HRV time series of healthy subjects and patients with cardiovascular diseases. Analysis with simulated signals show the LZ measure can vary depending on the adopted coding process. The binary coding, proposed in this work, is sensitive to the different dynamical systems generating the time series, as the ternary coding is sensitive to the presence of stationary states, i.e. a consecutive repetition of the same RR interval value. LZ method reliably differentiates healthy vs. disease group. Further clinical investigations on the LZ complexity and on its relationship to the risk of sudden death, can supply new diagnostic indications.
Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. 'Magnificent Milestones and Emerging Opportunities in Medical Engineering' (Cat. No.97CH36136)
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology
Parabolic flight induces modifications on left ventricular (LV) dimensions. By 2-D echocardiograp... more Parabolic flight induces modifications on left ventricular (LV) dimensions. By 2-D echocardiography we studied these changes induced by gravitational stresses. A semi-automatic LV endocardial border detection procedure based on level set methods was applied and LV cavity area computed frame-by-frame for a whole cardiac cycle during each gravity phase (1 Gz, 1.8 Gz, and 0 Gz). 8 subjects were studied
During a visual-motor task the movement strategies and the learning processes are investigated. A... more During a visual-motor task the movement strategies and the learning processes are investigated. A group of 10 normal young volunteers underwent the experiment. The EEG signal was recorded through the 10-20 acquisition system during the execution of a task after a visual input. Each subject repeated the movement several times in three different conditions: i) without knowledge of the performance; ii) with visual feedback; iii) with knowledge of the result. The signal was transformed through Laplacian operator in order to eliminate the spurious coherence and then time-variant coherence was calculated. Different trends of the coherence function have been evidenced in subjects learning and not learning the better movement strategy. In particular, relations have been found between frontal, central and occipital electrodes in medium and high frequency ranges.
Summary Objective: We introduce an algorithm for the automatic decomposition of Wigner Distributi... more Summary Objective: We introduce an algorithm for the automatic decomposition of Wigner Distribution (WD) and we applied it for the quantitative extraction of Heart Rate Variability (HRV) spectral parameters during non-stationary events. Early response to tilt was investigated. Methods: Quantitative analysis of multi-components non-stationary signals is obtained through an automatic decomposition of WD based on least square (LS) fitting of the instantaneous autocorrelation function (ACF). Through this approach the different signal and interference terms which contributes to the ACF may be separated and their parameters (instantaneous frequency and amplitude) quantified. A beat-to-beat monitoring of HRV spectral components is obtained. Results: Analysis of simulated signals demonstrated the capability of the proposed approach to track and separate the signal components. Analysis of HRV data evidenced different dynamics in the early Autonomic Nervous System (ANS) response to tilt. Conc...
2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006
The purpose of this work is to characterize the heart rate variability (HRV) of patients affected... more The purpose of this work is to characterize the heart rate variability (HRV) of patients affected by congestive heart failure (CHF) and to find out the main difference between this pathological condition and the physiological state. Parameters adopted in this work are: the detrended fluctuation analysis (DFA) and the Higuchi exponent to assess long correlations and self-similarity; the regularity estimators, approximate entropy (ApEn) and sample entropy (SampEn) and the multiscale entropy (MSE). Furthermore we proposed a new regularity index, the Gaussian entropy (GaussEn) which is a modification of the previous ApEn and SampEn. The results show the proposed parameters do an effective separation of physiological and pathological subject conditions. These results are part of a study evaluating the nonlinear index prognostic value toward cardiac death.
Proceedings of the 20th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. Vol.20 Biomedical Engineering Towards the Year 2000 and Beyond (Cat. No.98CH36286)
The paper presents a wavelet packets (WP) decomposition method for the post-processing of chemica... more The paper presents a wavelet packets (WP) decomposition method for the post-processing of chemical-shift 1H-MRS data and for an automatic computation of metabolic maps within anatomical brain regions. WP decomposition is used to analyze the recorded FID signals and to isolate the different metabolite contributions in different frequency bands. In each sub-band LPSDV method has been applied to compute the peak parameters. The main metabolic component are then automatically classified by using peak information such as center frequency and damping factor. The estimated peak amplitudes are then used to construct maps of metabolic concentrations in the analyzed region
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, 2011
The Amplitude of Dominant T-Wave Alternans (ADTWA) is a recently introduced index which quantifie... more The Amplitude of Dominant T-Wave Alternans (ADTWA) is a recently introduced index which quantifies the presence of microvolt T Wave Alternans (TWA) on surface ECG recordings. In this paper we investigate the reliability of ADTWA and its robustness against broadband noise. At this regard, we generated synthetic 12-leads ECG recordings through a forward electrophysiological model and we added TWA, at different extent, by modulating the variation of the repolarization times of transmembrane action potentials across even and odd beats. Using a stochastic model, we derived an analytical relationship between the repolarization variation injected into the model and TWA at the surface, thus offering a strategy to evaluate lead sensitivity. In terms of robustness, the results of the simulations show that ADTWA correctly measured the amplitude of synthetic TWA with an average error of 3.3% ± 5.8% in absence of noise. When a 100 μV peak-to-peak broadband noise is present, its effects on estimation errors were kept limited by singular value decomposition on which ADTWA builds.
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2006
The long term goal of our research is to develop a tool for recognizing human emotions during e-l... more The long term goal of our research is to develop a tool for recognizing human emotions during e-learning processes. This could be accomplished by combining quantitative indexes extracted from non-invasive recordings of four physiological signals: namely skin conductance, blood volume pulse, electrocardiogram and electroencephalogram. Wearable, non-invasive sensors, communicating with a PC, were applied to 30 students and data were collected during exposure to three different computer-mediated content stimuli designed to evoke specific emotional states: stress, relaxation and engagement. In this paper we describe both the general emotion evaluation algorithm, and present a preliminary results suggesting that some of the quantitative indexes may be successful in characterizing and distinguishing between the three different emotional states.
A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the h... more A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the heart rate variability (HRV) signal. The power spectrum is calculated from the AR coefficients derived from each single RR interval considered. Time-variant AR coefficients are determined through adaptive parametric identification with a forgetting factor which obtains weighed values on a running temporal window of 50 preceding measurements. Power spectrum density (PSD) is hence obtained at each cardiac cycle, making it possible to follow the dynamics of the spectral parameters on a beat-by-beat basis. These parameters are mainly the LF (low frequency) and the HF (high frequency) powers, and their ratio LF/HF. These together account for the balanced sympatho-vagal control mechanism affecting the heart rate. This method is applied to subjects suffering from transient ischemic attacks. The time variant spectral parameters suggest an early activation of LF component in the HRV power spectrum. It precedes by approximately 1.5-2 min the tachycardia and the ST displacement, generally indicative of the onset of an ischemic episode. The results suggest an arousal of sympathetic system before the acute attack.
Blood pressure variability is the result of a complex interaction between external stimulation an... more Blood pressure variability is the result of a complex interaction between external stimulation and several cardiovascular control mechanisms and is enhanced in all those conditions characterized by an impaired autonomic regulation of circulation. In particular, blood pressure variability is enhanced in hypertension over 24 h and may independently contribute to the cardiovascular complications of this condition. The paper by Mussalo and co-workers in this issue of Clinical Science offers additional information in this field by suggesting that different forms of hypertension are characterized by different patterns of blood pressure variability, and that these differences may reflect variations in the underlying autonomic regulation of the heart and blood vessels.
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society Volume 13: 1991
The monitoring of the patients in the Intensive Care Units requires the identification of several... more The monitoring of the patients in the Intensive Care Units requires the identification of several pressure parameters. This work proposes a monitoring system which evaluates the right and left heart performance using the pressure signal in both the ventricles and in the pulmonary artery. With a Swan-Ganz catheter with supplementary ventricular way we have obtained the continuous right ventricular and
The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society
We propose to study the heart rate variability (HRV) time series complexity by computing the Lemp... more We propose to study the heart rate variability (HRV) time series complexity by computing the Lempel Ziv complexity measure. LZ is sensitive to the rate of pattern recurrences in a time series. Analysis considers 24 h HRV time series of healthy subjects and patients with cardiovascular diseases. Analysis with simulated signals show the LZ measure can vary depending on the adopted coding process. The binary coding, proposed in this work, is sensitive to the different dynamical systems generating the time series, as the ternary coding is sensitive to the presence of stationary states, i.e. a consecutive repetition of the same RR interval value. LZ method reliably differentiates healthy vs. disease group. Further clinical investigations on the LZ complexity and on its relationship to the risk of sudden death, can supply new diagnostic indications.
Proceedings of the 19th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. 'Magnificent Milestones and Emerging Opportunities in Medical Engineering' (Cat. No.97CH36136)
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology
Parabolic flight induces modifications on left ventricular (LV) dimensions. By 2-D echocardiograp... more Parabolic flight induces modifications on left ventricular (LV) dimensions. By 2-D echocardiography we studied these changes induced by gravitational stresses. A semi-automatic LV endocardial border detection procedure based on level set methods was applied and LV cavity area computed frame-by-frame for a whole cardiac cycle during each gravity phase (1 Gz, 1.8 Gz, and 0 Gz). 8 subjects were studied
During a visual-motor task the movement strategies and the learning processes are investigated. A... more During a visual-motor task the movement strategies and the learning processes are investigated. A group of 10 normal young volunteers underwent the experiment. The EEG signal was recorded through the 10-20 acquisition system during the execution of a task after a visual input. Each subject repeated the movement several times in three different conditions: i) without knowledge of the performance; ii) with visual feedback; iii) with knowledge of the result. The signal was transformed through Laplacian operator in order to eliminate the spurious coherence and then time-variant coherence was calculated. Different trends of the coherence function have been evidenced in subjects learning and not learning the better movement strategy. In particular, relations have been found between frontal, central and occipital electrodes in medium and high frequency ranges.
Summary Objective: We introduce an algorithm for the automatic decomposition of Wigner Distributi... more Summary Objective: We introduce an algorithm for the automatic decomposition of Wigner Distribution (WD) and we applied it for the quantitative extraction of Heart Rate Variability (HRV) spectral parameters during non-stationary events. Early response to tilt was investigated. Methods: Quantitative analysis of multi-components non-stationary signals is obtained through an automatic decomposition of WD based on least square (LS) fitting of the instantaneous autocorrelation function (ACF). Through this approach the different signal and interference terms which contributes to the ACF may be separated and their parameters (instantaneous frequency and amplitude) quantified. A beat-to-beat monitoring of HRV spectral components is obtained. Results: Analysis of simulated signals demonstrated the capability of the proposed approach to track and separate the signal components. Analysis of HRV data evidenced different dynamics in the early Autonomic Nervous System (ANS) response to tilt. Conc...
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