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Papers by Louis-gilles Durand

Research paper thumbnail of Aortic Stenosis and Systemic Hypertension, Modeling of

Wiley Encyclopedia of Biomedical Engineering, Apr 14, 2006

Research paper thumbnail of Automatic detection of cardiac cycle based on an adaptive time-frequency analysis of the phonocardiogram

Demonstrates the feasibility of an adaptive time-frequency analysis, the matching pursuit method,... more Demonstrates the feasibility of an adaptive time-frequency analysis, the matching pursuit method, to detect each cardiac cycle of the phonocardiogram (PCG). The proposed new method combines a global search of the PCG in terms of energy distribution of the most important components with a local search according to the specific events found within a cardiac cycle. In the PCG recordings of twenty five patients, a detection rate of 96% was achieved. By eliminating the need for the recording of the electrocardiogram as the time-reference signal, this method reduces hardware and software overheads when analysis of PCG signals is primarily aimed. It is believed that, with minor modifications, this method can also be applied to extract different events of the PCG within a cardiac cycle. Furthermore, the procedure described in this paper can be applied to other kind of biomedical signals in order to extract coherent structures and identify specific events.

Research paper thumbnail of Effect of ensemble averaging on amplitude and feature variabilities of Doppler spectrograms recorded in the lower limb arteries

Medical & Biological Engineering & Computing, May 1, 1992

Research paper thumbnail of Time-frequency analysis of the first heart sound: Part 3: Application to dogs with varying cardiac contractility and to patients with mitral mechanical prosthetic heart valves

Medical & Biological Engineering & Computing, Sep 1, 1997

Research paper thumbnail of Cardiac Doppler blood-flow signal analysis

Medical & Biological Engineering & Computing, May 1, 1993

The normality (Gaussian property) and stationarity of the cardiac Doppler blood-flow signal were ... more The normality (Gaussian property) and stationarity of the cardiac Doppler blood-flow signal were evaluated on short-time segments distributed over the cardiac cycle. The basic approaches used to perform statistical tests on the nonstationary and quasiperiodic cardiac Doppler signal are presented. The results obtained from the data of ten patients having a normal aortic valve and ten patients having a stenotic

Research paper thumbnail of Review of the assessment of single level and multilevel arterial occlusive disease in lower limbs by duplex ultrasound

Ultrasound in Medicine and Biology, May 1, 1999

Research paper thumbnail of Comparison of spectral techniques for computer-assisted classification of spectra of heart sounds in patients with porcine bioprosthetic valves

Medical & Biological Engineering & Computing, May 1, 1993

The diagnostic performance of two spectral techniques (the fast Fourier transform, FFT, and autor... more The diagnostic performance of two spectral techniques (the fast Fourier transform, FFT, and autoregressive modelling, ARM) combined with four windowing functions (rectangular, Hanning, Hamming, and sine-cosine) and two classifiers (Bayes and nearest neighbour) to detect valvular degeneration was evaluated in a group of 95 patients. Forty-seven patients had a porcine bioprosthetic valve inserted in the aortic position and 48 patients had a porcine bioprosthetic valve inserted in the mitral position. Among the aortic valves, 24 were normal and 23 were degenerated whereas among the mitral valves, 19 were normal and 29 were degenerated. The aortic and mitral valves were analysed separately. For each type of valve, 21 features were extracted from the spectra of the valve closure sounds to train and test the performance of four pattern recognition systems by using the leave-one-out method. The discriminant properties of all feature combinations between two and five among the 21 features selected were evaluated. Results show that the FFT combined to the nearest neighbour classifier provided the best performances: 87 per cent of correct classifications (CCs) for aortic valves when using the Hanning or the Hamming window and 94 per cent of CCs for mitral valves when using the rectangular window. The best performances obtained with the ARM were 81 per cent of CCs for the aortic valves (nearest neighbour classifier and the Hanning or the Hamming window) and 92 per cent of CCs for the mitral valves (nearest neighbour classifier and the Hamming window or the Bayes classifier and the Hanning or the Hamming window).

Research paper thumbnail of Phonospirometry for noninvasive measurement of ventilation: methodology and preliminary results

Journal of Applied Physiology, Oct 1, 2002

Research paper thumbnail of Limitations of ultrasonic duplex scanning for diagnosing lower limb arterial stenoses in the presence of adjacent segment disease

Journal of Vascular Surgery, Apr 1, 1994

Research paper thumbnail of Modeling Of Blood Flow Transmission In Lower Limb Arteries Using Doppler Signals and Transfer Function

Research paper thumbnail of Pattern recognition of normal, lightly and heavily calcified bioprosthetic valves implanted in the mitral position

The performances of two pattern recognition methods for detecting and quantifying valvular degene... more The performances of two pattern recognition methods for detecting and quantifying valvular degeneration by spectral analysis of the first heart sound were evaluated in 48 patients with a porcine valve in the mitral position. Twenty patients had normal valves, 13 had lightly calcified valves, and 15 had heavily calcified valves. The pattern recognition methods were designed to classify the valve

Research paper thumbnail of The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability

Medical & Biological Engineering & Computing, Mar 1, 1992

Research paper thumbnail of Doppler velocity ratio measurements evaluated in a phantom model of multiple arterial disease

Ultrasound in Medicine and Biology, 1995

Research paper thumbnail of Extraction of new echo-Doppler diagnostic spectral parameters for detecting aortic stenosis

Parameters extracted from normalized spectrograms obtained by using the apical and left parastern... more Parameters extracted from normalized spectrograms obtained by using the apical and left parasternal windows have been investigated to characterize the blood flow disturbance below the aortic valve. The parameters proposed are based on the characterization of spectral broadening and on the evaluation of the power of the spectrograms in various frequency bands. Values for both normal and stenotic aortic valves

Research paper thumbnail of A method for studying the effects of PR and RR intervals on heart sound power spectra

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1988

In the course of exploring the potential of spectral analysis of valve closing sounds for the det... more In the course of exploring the potential of spectral analysis of valve closing sounds for the detection of valvular degeneration, a method was developed for determining, in a dog, the influence of PR interval (PRI) and heart rate (HR) on the spectra of intracardiac and thoracic first and second heart sounds. Preliminary results emphasize the strong dependence of the first

Research paper thumbnail of Application of Numerical Methods for Feature Extraction from Phonopneumograms

Journal of clinical engineering, Oct 1, 1985

ABSTRACT The application of numerical methods to the analysis of phonopneumograms is presented in... more ABSTRACT The application of numerical methods to the analysis of phonopneumograms is presented in this paper. The respiratory sounds, along with a synchronization signal indicating the duration of each event of the respiratory cycle, are recorded on magnetic tape by means of a portable cassette recorder. Subsequently, the two signals are digitized and processed on a microcomputer-based system. It is shown that synchronized Fourier analysis for spectral estimation, as well as Karhunen-Loeve transform for classification of spectra according to the pulmonary condition of the subjects, could provide information leading to a more objective evaluation of the lung condition from the respiratory sounds. (C)1985Aspen Publishers, Inc.

Research paper thumbnail of A Homomorphic Method To Recover The Intracardiac Left Ventricular Second Heart Sound

A signal processing method is proposed to recover intracardiac hcart sounds iroin externally reco... more A signal processing method is proposed to recover intracardiac hcart sounds iroin externally recorded phoiiocardiogranis (PCC;). The method uses a general model of sound transmission between the heart and the surface of the thorax, and it is based on deconvolution schemes in speech processing and seismology. An algorithm has been tested in recovering the left veiitriculas secoiid heart sound using

Research paper thumbnail of Time-frequency analysis of the muscle sound of the human diaphragm

Medical & Biological Engineering & Computing, Nov 1, 1997

Research paper thumbnail of Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs

Medical & Biological Engineering & Computing, Sep 1, 1990

A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventri... more A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventricular pacemaker after destruction of the bundle of His to produce a chronic heart block. The heart rate and P-R interval were then varied independently and their influence on the spectra and acoustic transmission of the mitral M1 and aortic A2 valve closure sounds was studied. Results indicate that the major effects of varying the P-R interval are a strong change in the intensity of M1 and modifications of its acoustic transmission across the heart/thorax acoustic system. No similar influence is observed on the intensity and acoustic transmission of A2. Varying the heart rate has a small effect of the intensity of M1 but none on the intensity of A2. In addition, changes in either the P-R interval or the heart rate do not seem to modify the spectral profile of the intracardiac and thoracic M1 and A2 components.

Research paper thumbnail of Animal blood models simulating normal, hypo- and hyperaggregating human red cells

Research paper thumbnail of Aortic Stenosis and Systemic Hypertension, Modeling of

Wiley Encyclopedia of Biomedical Engineering, Apr 14, 2006

Research paper thumbnail of Automatic detection of cardiac cycle based on an adaptive time-frequency analysis of the phonocardiogram

Demonstrates the feasibility of an adaptive time-frequency analysis, the matching pursuit method,... more Demonstrates the feasibility of an adaptive time-frequency analysis, the matching pursuit method, to detect each cardiac cycle of the phonocardiogram (PCG). The proposed new method combines a global search of the PCG in terms of energy distribution of the most important components with a local search according to the specific events found within a cardiac cycle. In the PCG recordings of twenty five patients, a detection rate of 96% was achieved. By eliminating the need for the recording of the electrocardiogram as the time-reference signal, this method reduces hardware and software overheads when analysis of PCG signals is primarily aimed. It is believed that, with minor modifications, this method can also be applied to extract different events of the PCG within a cardiac cycle. Furthermore, the procedure described in this paper can be applied to other kind of biomedical signals in order to extract coherent structures and identify specific events.

Research paper thumbnail of Effect of ensemble averaging on amplitude and feature variabilities of Doppler spectrograms recorded in the lower limb arteries

Medical & Biological Engineering & Computing, May 1, 1992

Research paper thumbnail of Time-frequency analysis of the first heart sound: Part 3: Application to dogs with varying cardiac contractility and to patients with mitral mechanical prosthetic heart valves

Medical & Biological Engineering & Computing, Sep 1, 1997

Research paper thumbnail of Cardiac Doppler blood-flow signal analysis

Medical & Biological Engineering & Computing, May 1, 1993

The normality (Gaussian property) and stationarity of the cardiac Doppler blood-flow signal were ... more The normality (Gaussian property) and stationarity of the cardiac Doppler blood-flow signal were evaluated on short-time segments distributed over the cardiac cycle. The basic approaches used to perform statistical tests on the nonstationary and quasiperiodic cardiac Doppler signal are presented. The results obtained from the data of ten patients having a normal aortic valve and ten patients having a stenotic

Research paper thumbnail of Review of the assessment of single level and multilevel arterial occlusive disease in lower limbs by duplex ultrasound

Ultrasound in Medicine and Biology, May 1, 1999

Research paper thumbnail of Comparison of spectral techniques for computer-assisted classification of spectra of heart sounds in patients with porcine bioprosthetic valves

Medical & Biological Engineering & Computing, May 1, 1993

The diagnostic performance of two spectral techniques (the fast Fourier transform, FFT, and autor... more The diagnostic performance of two spectral techniques (the fast Fourier transform, FFT, and autoregressive modelling, ARM) combined with four windowing functions (rectangular, Hanning, Hamming, and sine-cosine) and two classifiers (Bayes and nearest neighbour) to detect valvular degeneration was evaluated in a group of 95 patients. Forty-seven patients had a porcine bioprosthetic valve inserted in the aortic position and 48 patients had a porcine bioprosthetic valve inserted in the mitral position. Among the aortic valves, 24 were normal and 23 were degenerated whereas among the mitral valves, 19 were normal and 29 were degenerated. The aortic and mitral valves were analysed separately. For each type of valve, 21 features were extracted from the spectra of the valve closure sounds to train and test the performance of four pattern recognition systems by using the leave-one-out method. The discriminant properties of all feature combinations between two and five among the 21 features selected were evaluated. Results show that the FFT combined to the nearest neighbour classifier provided the best performances: 87 per cent of correct classifications (CCs) for aortic valves when using the Hanning or the Hamming window and 94 per cent of CCs for mitral valves when using the rectangular window. The best performances obtained with the ARM were 81 per cent of CCs for the aortic valves (nearest neighbour classifier and the Hanning or the Hamming window) and 92 per cent of CCs for the mitral valves (nearest neighbour classifier and the Hamming window or the Bayes classifier and the Hanning or the Hamming window).

Research paper thumbnail of Phonospirometry for noninvasive measurement of ventilation: methodology and preliminary results

Journal of Applied Physiology, Oct 1, 2002

Research paper thumbnail of Limitations of ultrasonic duplex scanning for diagnosing lower limb arterial stenoses in the presence of adjacent segment disease

Journal of Vascular Surgery, Apr 1, 1994

Research paper thumbnail of Modeling Of Blood Flow Transmission In Lower Limb Arteries Using Doppler Signals and Transfer Function

Research paper thumbnail of Pattern recognition of normal, lightly and heavily calcified bioprosthetic valves implanted in the mitral position

The performances of two pattern recognition methods for detecting and quantifying valvular degene... more The performances of two pattern recognition methods for detecting and quantifying valvular degeneration by spectral analysis of the first heart sound were evaluated in 48 patients with a porcine valve in the mitral position. Twenty patients had normal valves, 13 had lightly calcified valves, and 15 had heavily calcified valves. The pattern recognition methods were designed to classify the valve

Research paper thumbnail of The effect of averaging cardiac Doppler spectrograms on the reduction of their amplitude variability

Medical & Biological Engineering & Computing, Mar 1, 1992

Research paper thumbnail of Doppler velocity ratio measurements evaluated in a phantom model of multiple arterial disease

Ultrasound in Medicine and Biology, 1995

Research paper thumbnail of Extraction of new echo-Doppler diagnostic spectral parameters for detecting aortic stenosis

Parameters extracted from normalized spectrograms obtained by using the apical and left parastern... more Parameters extracted from normalized spectrograms obtained by using the apical and left parasternal windows have been investigated to characterize the blood flow disturbance below the aortic valve. The parameters proposed are based on the characterization of spectral broadening and on the evaluation of the power of the spectrograms in various frequency bands. Values for both normal and stenotic aortic valves

Research paper thumbnail of A method for studying the effects of PR and RR intervals on heart sound power spectra

Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1988

In the course of exploring the potential of spectral analysis of valve closing sounds for the det... more In the course of exploring the potential of spectral analysis of valve closing sounds for the detection of valvular degeneration, a method was developed for determining, in a dog, the influence of PR interval (PRI) and heart rate (HR) on the spectra of intracardiac and thoracic first and second heart sounds. Preliminary results emphasize the strong dependence of the first

Research paper thumbnail of Application of Numerical Methods for Feature Extraction from Phonopneumograms

Journal of clinical engineering, Oct 1, 1985

ABSTRACT The application of numerical methods to the analysis of phonopneumograms is presented in... more ABSTRACT The application of numerical methods to the analysis of phonopneumograms is presented in this paper. The respiratory sounds, along with a synchronization signal indicating the duration of each event of the respiratory cycle, are recorded on magnetic tape by means of a portable cassette recorder. Subsequently, the two signals are digitized and processed on a microcomputer-based system. It is shown that synchronized Fourier analysis for spectral estimation, as well as Karhunen-Loeve transform for classification of spectra according to the pulmonary condition of the subjects, could provide information leading to a more objective evaluation of the lung condition from the respiratory sounds. (C)1985Aspen Publishers, Inc.

Research paper thumbnail of A Homomorphic Method To Recover The Intracardiac Left Ventricular Second Heart Sound

A signal processing method is proposed to recover intracardiac hcart sounds iroin externally reco... more A signal processing method is proposed to recover intracardiac hcart sounds iroin externally recorded phoiiocardiogranis (PCC;). The method uses a general model of sound transmission between the heart and the surface of the thorax, and it is based on deconvolution schemes in speech processing and seismology. An algorithm has been tested in recovering the left veiitriculas secoiid heart sound using

Research paper thumbnail of Time-frequency analysis of the muscle sound of the human diaphragm

Medical & Biological Engineering & Computing, Nov 1, 1997

Research paper thumbnail of Spectral analysis and acoustic transmission of mitral and aortic valve closure sounds in dogs

Medical & Biological Engineering & Computing, Sep 1, 1990

A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventri... more A surgical protocol was designed to implant, in seven dogs, a programmable sequential atrioventricular pacemaker after destruction of the bundle of His to produce a chronic heart block. The heart rate and P-R interval were then varied independently and their influence on the spectra and acoustic transmission of the mitral M1 and aortic A2 valve closure sounds was studied. Results indicate that the major effects of varying the P-R interval are a strong change in the intensity of M1 and modifications of its acoustic transmission across the heart/thorax acoustic system. No similar influence is observed on the intensity and acoustic transmission of A2. Varying the heart rate has a small effect of the intensity of M1 but none on the intensity of A2. In addition, changes in either the P-R interval or the heart rate do not seem to modify the spectral profile of the intracardiac and thoracic M1 and A2 components.

Research paper thumbnail of Animal blood models simulating normal, hypo- and hyperaggregating human red cells