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The Energy Operator: A Useful Diagnostic Tool

The Energy Operator: A Useful Diagnostic Tool. Balu Santhanam SPCOM Lab, Dept. of E.E.C.E. University of New Mexico Email: bsanthan@eece.unm.edu. Overview of Talk. Energy Operator Primer. Biomedical Applications. Diagnostic Applications. ECG Example. Teager-Kaiser Energy Operator.

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The Energy Operator: A Useful Diagnostic Tool

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  1. The Energy Operator: A Useful Diagnostic Tool Balu Santhanam SPCOM Lab, Dept. of E.E.C.E. University of New Mexico Email: bsanthan@eece.unm.edu

  2. Overview of Talk • Energy Operator Primer • Biomedical Applications • Diagnostic Applications • ECG Example

  3. Teager-Kaiser Energy Operator • Continuous signals • Discrete Signals

  4. Higher-order Energy Operators Continuous Signals: Discrete Signals:

  5. Energy Separation Algorithm • Monocomponent AM-FM Signals: • Instantaneous Frequency (IF) and Amplitude (IA)

  6. Multi-band Demodulation • Filter signal via a bandpass filter-bank with optimized center-frequency and bandwidth. • Pick the most active branch based on the energy-operator output. • Demodulate output of selected branch using the ESA into IA/IF signals.

  7. Features of E - Operators (1) • The energy operator output for sinusoidal sources produces the normalized energy. • For slowly time-varying sources, the energy operator tracks the energy of the source. • Instantaneous behavior allows tracking of abrupt changes in energy.

  8. Features of E - Operators (2) • Higher-order energy operators track higher-order energies of a signal source. • For k = 2 : HOEO  TKEO. • Energy operators possess simplicity, efficiency and good time-resolution.

  9. Biomedical Applications • Used to detect vocal-tract defects and pathologies • Used to detect spikes in neural (EEG) output • Used for EEG segmentation and abrupt event detection. • Used for detection of heart murmurs, sleep apnea disorder, heart rate variability measurements.

  10. Vocal Tract Pathologies • Improper glottal closure: whisper phonation, creaky voice, glottal blow, etc. • Pathologies: polyps, papillomas, carcinoma, contact ulcers, nerve paralysis. • Vocal tract asymmetry produces two different fundamental frequencies • IA/IF estimates facilitate detection of normal/pathological cases.

  11. EEG Applications • EEG provides a sensitive indicator of cerebral function. • Spikes in the EEG output characterize epileptic seizures. • IA and IF information from segmented EEG serve as a useful diagnostic tools.

  12. Cardio Applications (1) • ECG signal exhibits quasi-periodicity producing regular peaks (R-waves) • Respiratory sinus arythmia (RSA) constitutes frequency modulation in the ECG signal. • The heart-IF (HIF) can be used to estimate heart-rate variability.

  13. Cardio Applications (2) • Instantaneous energy and IF can be used to classify heart sound and murmurs. • IA and IF of cardiac inter-beat times can be used to detect obstructive sleep-apnea (OSA). • Two component chirp model used to model pulmonary and aortic components of second heart sound (dub)

  14. ECG Example – 1

  15. ECG Example - 2

  16. ECG Example - 3

  17. ECGExample – 4

  18. References – 1 [BaOh01]: A. Barros and N. Ohnishi, “Heart Instantaneous Frequency (HIF): An alternative Approach to Extract Heart Rate Variability,” IEEE Trans. On Biomed. Engg., Aug, 2001. [Miet00]: J.E. Mietus et.al., “Detection of Obstructive Sleep Apnea from Cardiac Interbeat Interval Time Series,” Computers in Cardiology, 2000. [Shar00]: Sharif et. al., “Analysis and Classification of Heart Sounds and Murmurs Based on the Instantaneous Energy and Frequency Estimations,” Proceedings of TENCON, 2000. [MuRa98]: S. Mukhopadhyay and G.C. Ray, “A New Interpretation of Nonlinear Energy Operator and Its Efficacy in Spike Detection,” IEEE Trans. On Biomed. Engg. Feb. 2000.

  19. References - 2 • [XDP01]: J. Xu, L-G. Durand and P. Pibarot, “Nonlinear Transient Chirp Signal Modeling of the Aortic and Pulmonary Components of the Second Heart Sound,” IEEE Trans. On Biomed. Engg., March 2001. • [XDP00] : J. Xu, L-G. Durand and P. Pibarot, “Extraction of the Aortic and Pulmonary Components of the Second Heat Sound Using a Nonlinear Transient Chirp Signal Model,” IEEE Trans. On Biomed. Engg., July 2000. • [AgGo99]: R. Agarwal and J. Gotman, “Adaptive Segmentation of EEG Data Using A Nonlinear Energy Operator,” 1999. • [HCK98] : J.H.L. Hansen, L.G.-Ceballos, and J.F. Kaiser, “A Nonlinear Operator-Based Speech Feature Analysis Method with Application to Vocal Fold Pathology Assessment,” IEEE Trans. On Biomed. Engg., March 98

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