1 By By Elvir Causevic Elvir Causevic Department of Applied Mathematics Department of Applied Mathematics Yale University Yale University Founder and President Founder and President Everest Biomedical Instruments Everest Biomedical Instruments Fast Wavelet Estimation of Fast Wavelet Estimation of Weak Biosignals Weak Biosignals
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By Elvir Causevic Department of Applied Mathematics Yale University Founder and President
Fast Wavelet Estimation of Weak Biosignals. By Elvir Causevic Department of Applied Mathematics Yale University Founder and President Everest Biomedical Instruments. Overview. Introduction and Motivation Human auditory system - PowerPoint PPT Presentation
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ByBy
Elvir CausevicElvir Causevic
Department of Applied MathematicsDepartment of Applied Mathematics
Fast Wavelet Estimation of Fast Wavelet Estimation of Weak BiosignalsWeak Biosignals
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OverviewOverview
Introduction and Motivation Human auditory system Measurement of auditory function and difficulties in signal processing Introduction to wavelets and conventional wavelet denoising Novel wavelet denoising algorithm
Frame recombination Denoising Variable threshold selection Estimation of rate of convergence
Experimental results Future work Conclusion and summary
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IntroductionIntroduction Overall goalOverall goal
Creation of a fast estimator of weak biosignals based on Creation of a fast estimator of weak biosignals based on wavelet signal processing. Application to auditory wavelet signal processing. Application to auditory brainstem responses (ABRs) and other evoked potentialsbrainstem responses (ABRs) and other evoked potentials
Specific objectivesSpecific objectives Reduce the length of time to acquire a valid ABR signal.Reduce the length of time to acquire a valid ABR signal. Allow ABR signal acquisition in a noisy environment.Allow ABR signal acquisition in a noisy environment.
Key obstaclesKey obstacles Very large amount of acoustical and electrical noise Very large amount of acoustical and electrical noise
present .present . Signals collected from ear and brain have very low SNR Signals collected from ear and brain have very low SNR
and require long averaging timesand require long averaging times
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• Infant hearing screening is critically important in early Infant hearing screening is critically important in early intervention of treating deafness.intervention of treating deafness.
• Hearing loss affects 3 in 1,000 infants: most commonly occurring Hearing loss affects 3 in 1,000 infants: most commonly occurring birth defect.birth defect.
• 25,000 hearing impaired babies born annually in the U.S. alone.25,000 hearing impaired babies born annually in the U.S. alone.• Lack of early detection often leads to permanent loss of ability to Lack of early detection often leads to permanent loss of ability to
acquire normal language skills.acquire normal language skills.• Early detection allows intervention that commonly results in Early detection allows intervention that commonly results in
development of normal speech by school age.development of normal speech by school age.• Intervention involves hearing aids, cochlear implants and Intervention involves hearing aids, cochlear implants and
extensive parent and child education and training.extensive parent and child education and training.• 38 U.S. states mandate hearing screening, Europe, Australia, 38 U.S. states mandate hearing screening, Europe, Australia,
Asia following closely.Asia following closely.
Infant Hearing ScreeningInfant Hearing Screening
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Measurement of Hearing Measurement of Hearing FunctionFunction
Stimulus: 37 clicks per second, 65 dB SPL (30 dB nHL).Stimulus: 37 clicks per second, 65 dB SPL (30 dB nHL). Response: scalp electrodes measure μV level signals.Response: scalp electrodes measure μV level signals. Noise: completely buries the response (-35dB).Noise: completely buries the response (-35dB). Pass: signal to noise ratio measure (called Fsp) greater than an Pass: signal to noise ratio measure (called Fsp) greater than an
experimentally determined value (NIH Multicenter study).experimentally determined value (NIH Multicenter study). With linear averaging, reliable results are obtained within ~15 With linear averaging, reliable results are obtained within ~15
minutes of averaging of ~ 4000-8000 frames at a single level.minutes of averaging of ~ 4000-8000 frames at a single level. We would like to test multiple levels (up to 10) , and with multiple We would like to test multiple levels (up to 10) , and with multiple
tone pips (vs. clicks). This test normally takes over an hour, in a tone pips (vs. clicks). This test normally takes over an hour, in a sound attenuated booth, manually administered by an expert.sound attenuated booth, manually administered by an expert.
Currently only a single level response is tested and only a pass/fail Currently only a single level response is tested and only a pass/fail result is provided, with over 5% false positive rate.result is provided, with over 5% false positive rate.
Substantial improvement in rate of signal averaging is required to Substantial improvement in rate of signal averaging is required to obtain a full diagnostic and reliable test.obtain a full diagnostic and reliable test.
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Auditory Brainstem ResponseAuditory Brainstem Response example example
Signal Processing & Clinical IssuesSignal Processing & Clinical IssuesQuickTime™ and aGraphics decompressorare needed to see this picture. -100-90-80-70-60-50-40-30-20-100100100010000d
B V
Frequency in HzFrequency domain characteristics of a typical Frequency domain characteristics of a typical
ABR click stimulus as measured in the ear using the ER-10C ABR click stimulus as measured in the ear using the ER-10C transducer transducer
Experimental ResultsExperimental ResultsABR DataABR Data
0 2 4 6 8 10 12-1
0
1
2
3
4
5
6
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Linear Average and CSTD for ABR Data (Subject 3)128 frames with
1 =1
Latency after click presentation (ms)
Mag
nitu
de
(w
ith p
lotti
ng o
ffse
t)
Linear Avg.CSTD Final Avg.
0 2 4 6 8 10 12-1
0
1
2
3
4
5
Linear Average and CSTD for ABR Data (Subject 3)256 frames with
1 =1
Latency after click presentation (ms)
Mag
nitu
de
(w
ith p
lotti
ng o
ffse
t)
Linear Avg.CSTD Final Avg.
0 2 4 6 8 10 12-0.5
0
0.5
1
1.5
2
2.5
3
Linear Average and CSTD for ABR Data (Subject 3)512 frames with
1 =1
Latency after click presentation (ms)
Mag
nitu
de
(w
ith p
lotti
ng o
ffse
t)
Linear Avg.CSTD Final Avg.
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Experimental ResultsExperimental ResultsAMLR DataAMLR Data
V
Nb
PbPa
Time (ms)
Na
(e)
(a)
(b) (c)
(d)
Performance of CSTD algorithm compared to linear averaging 256 data frames. (a): Template Performance of CSTD algorithm compared to linear averaging 256 data frames. (a): Template of AMLR evoked potential waveform from Spehlmann; (b): linear average of 8192 AMLR of AMLR evoked potential waveform from Spehlmann; (b): linear average of 8192 AMLR
frames; (c): Single frame consisting of AMLR model plus WGN; (d): Linear average of 256 frames; (c): Single frame consisting of AMLR model plus WGN; (d): Linear average of 256 frames; (e): Result of CSTD algorithm frames; (e): Result of CSTD algorithm
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The Final ProductThe Final Product
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Future Work & Other Future Work & Other applicationsapplications
Wavelet denoising using wavelet packets EEG/EP Recording and Monitoring
• Use in ambulances and emergency roomsUse in ambulances and emergency rooms