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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
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Outline Introduction – the localization problem The method Results
New insights and conclusions
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Invasive Recordings - Subdural EEG (ECoG)
1-3 weeks recordings Voltage Time
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Invasive Recordings – Depth Electrodes
1-3 weeks recordings
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Inter-ictal Onset Ictal
The Challenge: Localization and assessment of the Epileptic foci Inter-ictal (before the seizure) Onset Ictal (The seizure)
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The Classical Frequency Bands
Delta: <3.5 Hz Theta: Hz Alpha: 7-13 Hz Beta: Hz Gamma: >30 Hz
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The Big Picture Similarity
42 HZ In all successful surgeries, the method detected the correct foci Frequency 0 HZ Similarity
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Time-Frequency Analysis – Some Math
Power Voltage Time Frequency The Fourier Transform Frequency basis Time basis
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Beyond Fourier Transform Time-Frequency Analysis
plane Frequency Time Signal
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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
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The Wavelet Transform Wavelet basis Binary tree
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Wavelet Packet Decomposition
Maximum Information Best Basis 70 31 32 11 12 13 4 9 8 2 3 5 6 7 (70)36 (31)23 (32)13 11 12 (13)9 4 9 8 2 3 5 6 7 “Shannon Information” Like Doron et al. Time-Invariant Person Specific Frequency Templates in Human Brain Activity,PRL. 96 (2006)
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Quantifying the Similarity
1/16 2/16 4/16 3/16 Wn
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Inter-Ictal Analysis: Similarity Matrices
Type I Type II
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Type I Type II
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Type I - Comparison Failed – the focus could not be removed
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Type II- Comparison Failed Partially successful Successful
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In all the successful surgeries
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
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Type I Type II
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Dynamics of Multiple Foci – For type II
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
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Thank you Summary The “world best method”
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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