Lecture 1: IntroductionBiomedical Signals and Systems

Ching-Han Hsu, Ph.D.

Fall 2015

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Signals are everywhere!!

Outline

1 Signals are everywhere!!

2 Natural Signals

3 Societal Signals

4 Bioelectric Signals

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Signals are everywhere!!

What is a signal?

Signals are elements of sensing, communication, control, andactuation processes.They convey data, messages, and information from the source to thereceiver and carry commands to influence the behavior of othersystems.A signal is a time-varying waveform such as in electricalcommunication, speech, computer and electronics, electromechanicalsystems, control systems, geophysical systems, biomedical systems,natural and societal systems.It represents variation in time, of a phenomenon such as air pressure,electric field, vibration, economic indicators, etc.

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Natural Signals

Outline

1 Signals are everywhere!!

2 Natural Signals

3 Societal Signals

4 Bioelectric Signals

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Natural Signals

Natural Signals

Sunspot NumbersAtmospheric CO2 ContentSeismic Signals

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Natural Signals Sunspot Numbers

Sunspot Numbers

In 1610, shortly after viewing the sun with his new telescope, GalileoGalilei made the first European observations of Sunspots.Continuous daily observations were started at the Zurich Observatoryin 1849.The sunspot number is calculated by first counting the number ofsunspot groups and then the number of individual sunspots.

http://solarscience.msfc.nasa.gov/SunspotCycle.shtml

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Natural Signals Sunspot Numbers

Sunspot

Figure 1: Detailed view, 13 December 2006.

https://en.wikipedia.org/wiki/SunspotChing-Han Hsu, Ph.D. Biom Signals & Systems Fall 2015 7 / 35

Natural Signals Sunspot Numbers

Sunspot Numbers: Periodic Functions?

Figure 2: Monthly averages(updated monthly) of thesunspot numbers show that thenumber of sunspots visible onthe sun waxes and wanes withan approximate 11-year cycle.

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Natural Signals Atmospheric CO2 Content

Atmospheric CO2 Content

Carbon dioxide (CO2) is the chief greenhouse gas that results fromhuman activities and causes global warming and climate change.The upper safety limit for atmospheric CO2 is 350 parts per million(ppm).Atmospheric CO2 levels have stayed higher than 350 ppm since early1988.The concentrations of CO2 in the atmosphere are increasing at anaccelerating rate from decade to decade.The 2014 average annual concentration of CO2 in the atmosphere(Mauna Loa Observatory) is 398.55 parts per million (ppm). The2013 average is 396.48 ppm.

http://co2now.org

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Natural Signals Atmospheric CO2 Content

Sunspot

Figure 3: 420,000 years of Atmospheric CO2 (grey line) plus Atmospheric methane (black line) compared with globaltemperature variations (red line). https://en.wikipedia.org/wiki/Sunspot

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Natural Signals Seismic Signals

Layered deformation in the Taiwan orogen

Layered deformation in the Taiwan orogen T.-Y. Huang, Y. Gung, B.-Y.Kuo, L.-Y. Chiao, and Y.-N. Chen Science 14 August 2015: 349 (6249),720-723. [DOI:10.1126/science.aab1879]http://www.sciencemag.org/content/349/6249/720.full

Three-dimensional (3D) tomographic models of shear-wave velocity(Vs) and its azimuthal variation for the crust of TaiwanUsing the empirical Green’s functions (EGF) of Rayleigh wavesextracted from ambient seismic noises.We resolve the detailed variations of seismic anisotropy from theshallow crust to about a 30-km depth.We implemented a wavelet-based multiscale inversion technique tosolve the simultaneous inversion for both isotropic and anisotropicmodels.

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Natural Signals Seismic Signals

Layered deformation in the Taiwan orogen

Figure 4: The Taiwan orogenand regional plate tectonics.

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Natural Signals Seismic Signals

Layered deformation in the Taiwan orogen

Figure 5: Cross sections showing rotation of anisotropy fabrics with depth.

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Natural Signals Seismic Signals

Layered deformation in the Taiwan orogen

Figure 6: Cartoon illustration of the layered deformation zones in the Taiwanorogen.

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Societal Signals

Outline

1 Signals are everywhere!!

2 Natural Signals

3 Societal Signals

4 Bioelectric Signals

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Societal Signals

Societal Signals

Dow Jones Industrial AverageUnemployment Rate

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Societal Signals Dow Jones Industrial Average

Dow Jones Industrial Average

The Dow Jones Industrial Average (DJIA) are maintained andreviewed by the Averages Committee.The DJIA index serves as a measure of the entire U.S. market,covering such diverse industries as financial services, technology,retail, entertainment and consumer goods.As a Yardstick. he most common use of an index by investors is toevaluate the performance of their own portfolios on a monthly orquarterly basis.As a Barometer. Like barometers measuring rising or falling airpressure, indexes can be used to help form judgments about thedirection in which the market is heading, and whether it is movingtentatively or certainly.

http://www.djaverages.com

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Societal Signals Dow Jones Industrial Average

Dow Jones Industrial Average

Figure 7: DJIA monthly trading volume in shares from 1929 to 2012.

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Societal Signals Unemployment Rate

Unemployment Rate

Unemployment occurs when people are without work and activelyseeking work.The unemployment rate is a measure of the prevalence ofunemployment.It is calculated as a percentage by dividing the number of unemployedindividuals by all individuals currently in the labor force.

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Societal Signals Unemployment Rate

Unemployment Rate

Figure 8: Taiwan Unemployment Rate

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Bioelectric Signals

Outline

1 Signals are everywhere!!

2 Natural Signals

3 Societal Signals

4 Bioelectric Signals

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Bioelectric Signals

Bioelectric Signals

Electrocardiogram Signals (ECG, EKG)Electromyogram Signals (EMG)Electroencephalogram Signals (EEG). . .

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Bioelectric Signals Electrocardiogram Signals (ECG, EKG)

Electrocardiogram Signals (ECG, EKG)

An electrocardiogram (ECG, EKG) is a test that records the electricalactivity of the heart.An ECG is used to measure:

Any damage to the heartHow fast your heart is beating and whether it is beating normallyThe effects of drugs or devices used to control the heart (such as apacemaker)The size and position of your heart chambers

Normal test results include:Heart rate: 60 to 100 beats per minuteHeart rhythm: consistent and even

https://www.nlm.nih.gov/medlineplus/ency/article/003868.htm

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Bioelectric Signals Electrocardiogram Signals (ECG, EKG)

Electrocardiogram Signals (ECG, EKG)

Figure 9: The image shows the standard setup for an EKG. In figure A, a normal heart rhythm recording shows the electricalpattern of a regular heartbeat. In figure B, a patient lies in a bed with EKG electrodes attached to his chest, upper arms, andlegs. A nurse monitors the painless procedure.https://www.nhlbi.nih.gov/health/health-topics/topics/ekg/during

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Bioelectric Signals Electrocardiogram Signals (ECG, EKG)

Electrocardiogram Signals (ECG, EKG)

Figure 10: ECG of a heart innormal sinus rhythm. http://global.britannica.com

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Bioelectric Signals Electrocardiogram Signals (ECG, EKG)

What Abnormal ECG Results Mean

Abnormal ECG results may be a sign of:Damage or changes to the heart muscleChanges in the amount of the electrolytes (such as potassium andcalcium) in the bloodCongenital heart defectEnlargement of the heartFluid or swelling in the sac around the heartInflammation of the heart (myocarditis)Past or current heart attackPoor blood supply to the heart arteriesAbnormal heart rhythms (arrhythmias)

https://www.nlm.nih.gov/medlineplus/ency/article/003868.htm

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Bioelectric Signals Electromyogram Signals (EMG)

Electromyogram Signals (EMG)

The EMG is the signal that can be recorded by electrodes from anactive muscle.Branches of a nerve fibre each activate the motor endplate of amuscle fibre.This induces two depolarization waves which travel at a speed of 3-6m/set to either end of the muscle fibre.Electrical signals related to the fibre depolarization can therefore berecorded by electrodes at some distance from the fibre: the EMG.

Hof, Human Movement Science, 1984

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Bioelectric Signals Electromyogram Signals (EMG)

Electromyogram Signals (EMG)

Figure 11: Schematic representation of the detection and decomposition ofintramuscular EMG signals.

http://rsta.royalsocietypublishing.org/content/367/1887/357Ching-Han Hsu, Ph.D. Biom Signals & Systems Fall 2015 28 / 35

Bioelectric Signals Electromyogram Signals (EMG)

Electromyogram Signals (EMG)

EMGs can be used to detect abnormal electrical activity of muscle thatcan occur in many diseases and conditions, including

muscular dystrophy,inflammation of muscles,pinched nerves,peripheral nerve damage (damage to nerves in the arms and legs),amyotrophic lateral sclerosis (ALS),myasthenia gravis,disc herniation,and others.

http://www.medicinenet.com/electromyogram

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Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

The first recording of the electric field of the human brain was madeby the German psychiatrist Hans Berger in 1924 in Jena.An electroencephalogram (EEG) is a test to measure the electricalactivity of the brain.The recorded waveforms reflect the cortical electrical activity.Signal intensity: EEG activity is quite small, measured in microvolts(µ V).Signal frequency: the main frequencies of the human EEG waves are:

Delta: has a frequency of 3 Hz or below.Theta: has a frequency of 3.5 to 7.5 Hz and is classified as ”slow”activity.Alpha: has a frequency between 7.5 and 13 Hz.Beta: beta activity is ”fast” activity. It has a frequency of 14 andgreater Hz.

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Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

Figure 12: The international 10-20 system seen from (A) left and (B) above thehead. A = Ear lobe, C = central, Pg = nasopharyngeal, P = parietal, F =frontal, Fp = frontal polar, O = occipital.

http://www.bem.fi/book/Ching-Han Hsu, Ph.D. Biom Signals & Systems Fall 2015 31 / 35

Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

Figure 13: The international10-20 system seen from (C)Location and nomenclature ofthe intermediate 10% electrodes,as standardized by the AmericanElectroencephalographic Society.

http://www.bem.fi/book/

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Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

Figure 14: Epileptic spike andwave discharges monitored withEEG.

https://en.wikipedia.org/wiki/Electroencephalography

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Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

Figure 15: If instead you wanted to record the response of a human visual cortexneuron (located in the back of your head) in response to light...https://backyardbrains.com/experiments/eeg

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Bioelectric Signals Electroencephalogram Signals (EEG)

Electroencephalogram Signals (EEG)

Figure 16: In general, the more synchronous the neurons in your brain are, theless data processing is occurring.https://backyardbrains.com/experiments/eeg

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