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Localization and Assessment of Epileptic Foci A new method using Wavelet Packets

Localization and Assessment of Epileptic Foci A new method using Wavelet Packets. Tomer Gazit (BIU & TAU). With. Itai Doron, Eden Rephaeli (TAU). Eshel Ben-Jacob (TAU). Oren Sagher – Dep. Of Neurosurgery, Univ. of Michigan Health System

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Localization and Assessment of Epileptic Foci A new method using Wavelet Packets

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  1. Localization and Assessment of Epileptic Foci A new method using Wavelet Packets Tomer Gazit (BIU & TAU) With Itai Doron, Eden Rephaeli (TAU) Eshel Ben-Jacob (TAU) Oren Sagher – Dep. Of Neurosurgery, Univ. of Michigan Health System Leo V. Towle – Dep. Of Neurology, Univ. of Chicago Hospitals Epilepsy Workshop, Michigan, May 9

  2. Outline • Introduction – the localization problem • The method • Results • New insights and conclusions

  3. Voltage Time Invasive Recordings - Subdural EEG (ECoG) 1-3 weeks recordings

  4. Invasive Recordings – Depth Electrodes 1-3 weeks recordings

  5. The Challenge: Localization and assessment of the Epileptic foci Inter-ictal (before the seizure) Onset Ictal (The seizure)

  6. The Classical Frequency Bands Delta: <3.5 Hz Theta: 3.5-7 Hz Alpha: 7-13 Hz Beta: 13-30 Hz Gamma: >30 Hz

  7. The Big Picture 42 HZ In all successful surgeries, the method detected the correct foci Frequency 0 HZ Similarity

  8. Time-Frequency Analysis – Some Math Power Voltage Time Frequency The Fourier Transform Frequency basis Time basis

  9. Beyond Fourier Transform Time-Frequency Analysis Time-Frequency plane Frequency Time Signal

  10. Wavelets A “mother wavelet” is a function located in time and frequency. The Mexican Hat The function is dilated and time-shifted to form a set of basis functions: The Coiflet

  11. The Wavelet Transform Wavelet basis Binary tree

  12. 2 2 4 4 3 3 32 (32)13 4 4 13 (13)9 5 5 70 (70)36 6 6 12 12 7 7 31 (31)23 8 8 11 11 9 9 Wavelet Packet Decomposition Maximum Information Best Basis “Shannon Information” Like Doron et al. Time-Invariant Person Specific Frequency Templates in Human Brain Activity,PRL. 96 (2006)

  13. Quantifying the Similarity 1/16 2/16 4/16 3/16 Wn

  14. Inter-Ictal Analysis: Similarity Matrices Type I Type II

  15. Type I Type II

  16. Type I - Comparison Failed – the focus could not be removed

  17. Type II- Comparison Failed Partially successful Successful Partially successful

  18. Results - 11 Patients Type I Type II 7 Patients 4 Patients 6 successful surgeries 1 successful surgery 1 Failed (Focus could not be removed) 3 Non-successful In all the successful surgeries the resected zones matched the predicted foci In all the non-successful surgeries One (or more) predicted focus was not resected

  19. Type I Type II

  20. Looking Ahead The Middle Ages The Iron Age The patient survived the surgery Can we do better? Dynamics of Multiple Foci – For type II Early Warning Scalp EEG Epilepsy Pace-Maker

  21. Summary New methods for: Localization and Assessments of Epileptic Foci 1. Identification of two Types of Seizure Dynamics 2. Satisfying agreement with surgery results 3. New insights We do not seek: The “world best method” and not to replace the Epileptologists We hope that one day The methods will be used for diagnostics Thank you

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