Unit 3 biomedical

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MEDICAL ELECTRONICS

Mr. DEEPAK P.Associate ProfessorECE Department

SNGCE

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EEG, EMG, Telemetry

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EEG

Electroencephalography (EEG)Electroencephalography (EEG) is the recording of electrical

activity along the scalp.

EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain.

Electroencephalogram (EEG) was first measured in humans by Hans Berger in 1929.

EEG is most often used to diagnose epilepsy, which causes abnormalities in EEG readings.

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Electroencephalography (EEG)It is the recording of bioelectric potentials generated by the

neuronal activity of the brain.

It is very difficult to recognize than ECG.

It is usually measured at the surface of the scalp.

Frequency of the EEG waves related to the mental activity of a person

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Electroencephalography (EEG)Spontaneous activity is measured on the scalp or on the

brain and is called the electroencephalogram.

The amplitude of the EEG is about 100 µV when measured on the scalp, and about 1-2 mV when measured on the surface of the brain.

Evoked potentials are those components of the EEG that arise in response to a stimulus

Single-neuron behavior can be examined through the use of microelectrodes which impale the cells of interest.

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Electroencephalography (EEG)

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Electroencephalography (EEG)

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EEG FREQUENCY BANDS

Electroencephalography (EEG)It is also used to diagnose sleep disorders, coma, and brain

death

Among the basic waveforms are the alpha, beta, theta, and delta rhythms.

Alpha waves occur at a frequency of 8 to 12 cycles per second in a regular rhythm.

They are present only when you are awake but have your eyes closed.

Usually they disappear when you open your eyes or start mentally concentrating.

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Electroencephalogram (EEG)

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The various frequency ranges of EEG are

Delta(∆)-----3.5 Hz-----Deep sleep

Theta(Ø)----3.5 to 8 HZ------ drowsiness(Tired)

Alpha(α)-----8 HZ to 13 HZ----- Relaxed but alert

Beta(β)--Above 13 HZ up to 30 HZ-- Highly alert and focused

Gama(γ)------ 30–100 Hz

Electroencephalogram (EEG)

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EEG wavesDelta waves

Theta

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EEG wavesAlpha waves

Beta

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EEG wavesGama waves

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Electroencephalography (EEG)Beta waves occur at a frequency of 13 to 30 cycles per second.

They are usually associated with anxiety, depression, or the use of sedatives.

Theta waves occur at a frequency of 4 to 7 cycles per second.

They are most common in children and young adults.

Delta waves occur at a frequency of 0.5 to 3.5 cycles per second.

They generally occur only in young children during sleep.

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Electroencephalography (EEG).

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Electroencephalography (EEG)When the eyes are closed, the alpha waves begin to dominate

the EEG. When the person falls asleep, the dominant EEG frequency

decreases. In a certain phase of sleep, rapid eye movement called

(REM) sleep, the person dreams and has active movements of the eyes, which can be seen as a characteristic EEG signal.

In deep sleep, the EEG has large and slow deflections called delta waves.

No cerebral activity can be detected from a patient with complete cerebral death.

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EVOKED POTENTIALS

Evoked PotentialsDerivatives of the EEG technique include evoked potentials

(EP), which involves averaging the EEG activity to a stimulus of some sort (visual, somatosensory, or auditory).

orSensory evoked potentials (SEP) are recorded from the central

nervous system following stimulation of sense organs

Event-related potentials (ERPs) refer to averaged EEG responses that are time-locked to more complex processing of stimuli

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Evoked Potentials.

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EEG RECORDER

Electroencephalography (EEG)EEG machine consists of the following components1- Electrodes.2- Amplifiers.3- Filters. 4- Recording unit.

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EEG Recorder

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Analog EEG

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Digital EEG Simple Block Diagram

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Digital EEG

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EEG Mechine

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EEG ARTIFACTS

Electroencephalography (EEG)Since EEG signals are very weak (ranging from 1 to 100 V),

they can easily be contaminated by other sources. An EEG signal that does not originate from the brain is called an

artifact. The amplitude of artifacts can be quite large relative to the size

of amplitude of the cortical signals of interest.

Artifacts can be divided into two categories: Physiologic and non-physiologic

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EEG ELECTRODE

EEG Electrode PlacementNormal EEG waves

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Electrode Placement

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Electrodes are small, disposable, self-adhesive and contain their own electrode gel.

The EEG is usually recorded with the subject awake but resting on a bed with their eyes closed.

EEG Electrodes

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Electrode Placement

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1.Bipolar (between pairs of electrodes, usually adjacent)

2. Monopolar (between one electrode and a distant reference electrode usually attached to one or both earlobes)

3. Monopolar (between one electrode and a reference formed by averaging all the other electrodes by connecting them through resistors)

Electrode Placement

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Electrode Placement

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EEG Electrodes SystemThere are two system of electrode placement:1- 10-20 international system: includes 21 electrodes.2- 10-10 international system: includes 64 electrodes.

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EEG Electrodes SystemThe numbers ‘10’ and ‘20’ refer to the fact that the distances

between adjacent electrodes are either 10% or 20% of the total front- back or right-left distance of the skull.

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FP= Frontal Polar

EEG Electrodes System

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EMG

Electromyogram (EMG)Electromyography (EMG) is a technique for evaluating and

recording the electrical activity produced by skeletal muscles.

EMG is performed using an instrument called an electromyograph

An Electromyograph detects the electrical potential generated by muscle cells when these cells are electrically or neurologically activated

Measured EMG potentials range between less than 50 μV and up to 20 to 30 mV, depending on the muscle under observation.

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Electromyogram (EMG)

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Electromyogram (EMG)EMG is used as a diagnostics tool for identifying neuromuscular

diseases.

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Electromyogram (EMG)An electromyogram (EMG) measures the electrical activity of

muscles at rest and during contraction.

Nerve conduction studies measure how well and how fast the nerves can send electrical signals.

Body temperature can affect the results of this test.

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EMG ELECTRODEEMG is used clinically for the diagnosis of neurological and

neuromuscular problems.There are two kinds of EMG in widespread use: 1. Surface EMG 2. Intramuscular (needle and fine-wire) EMG.

• A surface electrode may be used to monitor the general picture of muscle activation

• To perform intramuscular EMG, a needle electrode or a needle containing two fine-wire electrodes is inserted through the skin into the muscle tissue.

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EMG RECORDER

Simple Block diagram (EMG)

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PRE-AMPLIFIER

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Properties of an ideal pre-amplifier

High common mode rejection ratio

Very high input impedance

Short distance to the signal source

Strong DC signal suppression

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Analog EMG Block diagram

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Digital EMG Block diagram

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Digital EMG Block diagram

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PATIENT MONITORING

Patient Monitoring• Patient monitoring is nothing but continuous monitoring of

patient using electronic equipments.• A patient monitor is a medical device used for monitoring the

health status of patients. • Patient monitors are also called medical monitors or

physiological monitors.• It can be performed by continuously measuring certain

parameters by using a medical monitor (for example, by continuously measuring vital signs by a bedside monitor), and/or by repeatedly performing medical tests (such as blood glucose monitoring with a glucose meter).

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Patient MonitoringTransmitting data from a monitor to a distant monitoring

station is known as telemetry or biotelemetry.Monitoring of vital parameters can include several of the ones

mentioned above, and most commonly include at least blood pressure and heart rate, and preferably also pulse oximetry and respiratory rate.

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Patient MonitoringMonitoring can be classified by the target of interest, including:Cardiac monitoring, which generally refers to continuous

electrocardiography with assessment of the patients condition relative to their cardiac rhythm.

Hemodynamic monitoring, which monitors the blood pressure and blood flow within the circulatory system.

Respiratory monitoring,Pulse oximetry which involves measurement of the saturated

percentage of oxygen in the blood, referred to as SpO2, and measured by an infrared finger cuff Capnography, which involves CO2 measurements,

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Bed -Side Monitor

Patient MonitoringIn medicine, monitoring is the observation of a disease, condition or one or several medical parameters over time.

It can be performed by continuously measuring certain parameters by using a medical monitor

Transmitting data from a monitor to a distant monitoring station is known as telemetry or biotelemetry.

Vital signs (often shortened to just vitals) are used to measure the body’s basic functions

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Patient MonitoringVital measurements are taken to help assess the general physical health of a person, give clues to possible diseases.

There are four primary vital signs: body temperature, blood pressure, pulse (heart rate), and breathing rate (respiratory rate).

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Patient Monitoring in ICU

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Simple Block Diagram of Patient Monitoring

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Automaticcontrol

Patient equipment Computer DBMS

Reports

Mouse andkeyboard

Display

Transducers

Clinician

Bed-Side Monitor

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Measuring ParametersCardiac monitoring: Electrocardiography Cardiac output

Hemodynamic blood pressure and blood flow

Respiratory monitoring: Pulse oximetry,Capnography, airway respiratory rate)

Blood glucose monitoring

Childbirth monitoring

Body temperature monitoring

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Central Monitor

Central Monitoring

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Physiological data

Bedside Monitors

Hard wire Remote Link

From other bedsCentral Monitor Console

Central Monitoring

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Cardiac Tachometer

TachometerTachometer is generally used for measuring the speed Tachometer can be classified in to

1.Analog Tachometer– It consists of needle and dial.

2.Digital Tachometer-- It consists of memory, LCD and LED

3.Contact Tachometer–Sensor is directly contact with rotor

4.Non Contact Tachometer

5.Time/ Frequency measurement Tachometer

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Non-Contact Tachometer• Non Contact Tachometer is classified into

1. Inductive type

2. Capacitive type

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Non-Contact Tachometer

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Applications Tachometer• It is commonly used in automobiles and machineries.

• It is used in automobiles to indicate the rotation rate of crank shaft of engine.

• Used to estimate the traffic speed of vehicles.

• Used in medical field to measure the heart rate , blood flow rate, respiratory gas flow rate.

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Cardiac Tachometer Heart rate can be measured either by calculating the average or

instantaneous time interval between two R peaks.

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Cardiac Tachometer

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Cardiac Tachometer

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Cardiac Tachometer

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Cardiac Tachometer

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Block Diagram of Digital Cardiac Tachometer

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Digital Cardiac Tachometer• It senses the heart beat from finger tip using IR reflection method

• When heart contracts, the volume of blood in the finger tip decreases.

• When heart expands, the volume of blood in the finger tip increases.

• The resultant pulsing of blood volume inside the tip is proportional to heart rate.

•

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Digital Cardiac Tachometer• IR TX-RX pair is placed in finger tip with close contact.

• The reflected IR wave is sensed by the circuit.

• The intensity of the reflected wave is proportional to the volume of blood in the finger tip.

•

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IR Sensor

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Cardiac Tachometer

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Cardiac Tachometer

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Cardiac Tachometer

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Alarms

Comparator Alarm Circuits

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To alarm circuit

Comparator Alarm CircuitsA comparator circuit compares two voltage signals and determines which one is greater.

The result of this comparison is indicated by the output voltage

If the op-amp's output is saturated in the positive direction, the non inverting input (+) is a greater, or more positive, voltage than the inverting input (-).

If the op-amp's voltage is near the negative supply voltage (in this case, 0 volts, or ground potential), it means the inverting input (-) has a greater voltage applied to it than the non inverting input (+).

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Comparator Alarm Circuits

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Alarm Circuits for Cardiac Tachometer

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Lead Fault Indicator

Lead fault indicator

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Lead fault indicatorWhen a monitor electrode or lead wire comes loose, the appearance of display will be either a base line or 60Hz interface.

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Bio Telemetry

Bio-TelemetryThe term telemetry is derived from the two Greek terms: “tele”

and “metron”, which mean “remote” and “measure”.

In general, a physical variable or quantity under measurement, whether local or remote, is called a measurand.

Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator.

Literally, biotelemetry is the measurement of biological parameters over a distance.

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Bio-TelemetryStethoscope is the simple example for bio telemetry.

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Elements of Bio Telemetry

Elements of Telemetry

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Elements of Telemetry1. Transducer or Sensor: • Converts the physical variable to be telemetered into an

electrical quantity.2. Signal Conditioner-1: • Converts the electrical output of the transducer (or sensor)

into an electrical signal compatible with the transmitter.3. Transmitter: • Its purpose is to transmit the information signal coming

from the signal conditioner-1 using a suitable carrier signal to the receiving end.

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Elements of TelemetryThe transmitter may perform one or more of the following

functions:(i) Modulation: Modulation of a carrier signal by the

information signal.(ii) Amplification: As and if required for the purpose of

transmission.(iii) Signal Conversion: As and if required for the purpose of

transmission.(iv) Multiplexing: If more than one physical variables need to

be telemetered simultaneously from the same location, then either frequency-division multiplexing (FDM) or time-division multiplexing (TDM) is used.

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Elements of TelemetryReceiver: Its purpose is to receive the signal(s) coming from

the transmitter (located at the sending end of the telemetry system) via the signal transmission medium and recover the information from the same.

It may perform one or more of the following functions:1. Amplification2. Demodulation:3. Reverse Signal Conversion4. De-multiplexing

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Elements of TelemetrySignal Conditioner-2: Processes the receiver output as

necessary to make it suitable to drive the given end device.End Device: The element is so called because it appears at the

end of the system.

End device may be performing one of the following functions:

1. Analog Indication:2. Digital Display3. Digital Storage4. Data Processing5. Closed-Loop Control

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Subsystems of Telemetry System(a) Measurement Subsystem:

It comprises the transducer (or sensor), signal conditioner and the end device, like any conventional measurement system.

(b) Communication Subsystem: It comprises the transmitter and receiver along with the

transmission medium linking the two, like any communication system.

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Classifications of Bio Telemetry

Telemetry Classification Based on Transmission Medium

1. Wire-Link Telemetry or Wire Telemetry2. Radio Telemetry or Wireless Telemetry

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Wired Bio Telemetry

Wired Telemetry

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Elements of Wired Bio-Telemetry(Analog)

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Digital Wired Bio Telemetry

Elements of Wired Bio-Telemetry(Digital)

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Elements of Wired Digital Bio-Telemetry

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Wireless Bio Telemetry

Elements of Wireless Bio-Telemetry Using wireless bio telemetry, physiological signals can be

obtained from swimmers, riders, athlets, pilots or manual labours.

• It is two types1. Short-Range Radio Telemetry2. Satellite-Radio Telemetry

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Elements of Wireless Bio-TelemetryA typical biotelemetry system comprises:

1. Sensors appropriate for the particular signals to be monitored

2. Battery-powered, Patient worn transmitters3. A Radio Antenna and Receiver4. A display unit capable of concurrently presenting

information from multiple patients

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Elements of Basic Wireless Bio-Telemetry

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Elements of Wireless Bio-Telemetry

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Elements of Wireless Bio-Telemetry

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Wireless Bio-telemetry Transmitter

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Wireless Bio-telemetry Receiver

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Portable Bio Telemetry

Portable Telemetry

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Portable Telemetry

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Bio Telemetry Modulation

Telemetry Classification Based on Modulation MethodDC Telemetry Systems

1. Direct voltage telemetry system2. Direct current telemetry system

AC Telemetry Systems1. Amplitude modulation (AM) telemetry system2. Frequency modulation (FM) telemetry system

Pulse Telemetry Systems1. Pulse amplitude modulation (PAM) telemetry system2. Pulse width modulation (PWM) telemetry system3. Pulse phase modulation (PPM) telemetry system4. Pulse frequency modulation (PFM) telemetry system5. Pulse code modulation (PCM) telemetry system

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Direct Current Telemetry

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FM Radio Telemetry

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Single Channel Bio Telemetry

Single Channel PWM Telemetry

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Single Channel PCM Telemetry

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Choice of Carrier frequency

Choice of Carrier Frequency In every country there are regulations for the use of frequency

for medical telemetry.

The radio frequencies normally used for medical telemetry purposes are of the order of 37, 102, 153, 159, 220 and 450 MHz.

In USA, two frequency bands (174-216MHz and 450-470MHz) are used.

The transmitter is typically 50mW .

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Engineering

Unit 3 biomedical