5th semester subject - medical electronics

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MEDICAL ELECTRONICS
Mr. DEEPAK P.
Associate Professor
ECE Department
SNGCE
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2. EEG, EMG, Telemetry
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UNIT 3
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EEG

4. 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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5. 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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6. 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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7. Electroencephalography (EEG)
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8. Electroencephalography (EEG)
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EEG FREQUENCY BANDS

10. 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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11. 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

12. Electroencephalogram (EEG)
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13. EEG waves
Delta waves
Theta
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14. EEG waves
Alpha waves
Beta
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15. EEG waves
Gama waves
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16. 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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17. Electroencephalography (EEG)
.
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18. Electroencephalography (EEG)
.
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19. Electroencephalography (EEG)
.
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20. 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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21. Electroencephalography (EEG)
.
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EVOKED POTENTIALS

23. Evoked Potentials
Derivatives of the EEG technique include evoked potentials
(EP), which involves averaging the EEG activity to a stimulus
of some sort (visual, somatosensory, or auditory).
or
Sensory 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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24. Evoked Potentials
.
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EEG RECORDER

26. Electroencephalography (EEG)
EEG machine consists of the following components
1- Electrodes.
2- Amplifiers.
3- Filters.
4- Recording unit.
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27. EEG Recorder
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28. Analog EEG
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29. Digital EEG Simple Block Diagram
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30. Digital EEG
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31. EEG Mechine
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EEG ARTIFACTS

33. 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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34. Electroencephalography (EEG)
.
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EEG ELECTRODE

36. EEG Electrode Placement
Normal EEG waves
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37. 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.

38. EEG Electrodes
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39. 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)

40. Electrode Placement
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41. Electrode Placement
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42. EEG Electrodes System
There 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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43. EEG Electrodes System
The 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

44. EEG Electrodes System
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45. EEG Electrodes System
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46. EEG Electrodes System
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EMG

48. 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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49. Electromyogram (EMG)
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50. Electromyogram (EMG)
EMG is used as a diagnostics tool for identifying neuromuscular
diseases.
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51. 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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52. Electromyogram (EMG)
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53. Electromyogram (EMG)
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54. EMG ELECTRODE
EMG 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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55. Electromyogram (EMG)
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56. Electromyogram (EMG)
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EMG RECORDER

58. Simple Block diagram (EMG)
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59. PRE-AMPLIFIER
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60. 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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61. Analog EMG Block diagram
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62. Digital EMG Block diagram
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63. Digital EMG Block diagram
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PATIENT MONITORING

65. 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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66. Patient Monitoring
Transmitting 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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67. Patient Monitoring
Monitoring 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

69. Patient Monitoring
In 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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70. Patient Monitoring
Vital 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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71. Patient Monitoring in ICU
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72. Simple Block Diagram of Patient Monitoring
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Automatic
control
Patient equipment Computer DBMS
Reports
Mouse and
keyboard
Display
Transducers
Clinician

73. Bed-Side Monitor
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74. Measuring Parameters
Cardiac 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

76. Central Monitoring
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Physiological data
Bedside Monitors
Hard wire Remote Link
From other beds
Central Monitor Console

77. Central Monitoring
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Cardiac Tachometer

79. Tachometer
Tachometer 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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80. Non-Contact Tachometer
• Non Contact Tachometer is classified into
1. Inductive type
2. Capacitive type
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81. Non-Contact Tachometer
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82. 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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83. Cardiac Tachometer
 Heart rate can be measured either by calculating the average or
instantaneous time interval between two R peaks.

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84. Cardiac Tachometer
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85. Cardiac Tachometer
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86. Cardiac Tachometer
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87. Cardiac Tachometer
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88. Block Diagram of Digital Cardiac Tachometer
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89. 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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90. 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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91. IR Sensor
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92. Cardiac Tachometer
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93. Cardiac Tachometer
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94. Cardiac Tachometer
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Alarms

96. Comparator Alarm Circuits
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To alarm circuit

97. Comparator Alarm Circuits
A 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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98. Comparator Alarm Circuits
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99. Alarm Circuits for Cardiac Tachometer
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Lead Fault Indicator

101. Lead fault indicator
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102. Lead fault indicator
When 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

104. Bio-Telemetry
The 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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105. Bio-Telemetry
Stethoscope is the simple example for bio telemetry.
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Elements of Bio Telemetry

107. Elements of Telemetry
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108. Elements of Telemetry
1. Transducer or Sensor:
• Converts the physical variable to be telemetered into an
electrical quantity.
1. Signal Conditioner-1:
• Converts the electrical output of the transducer (or sensor)
into an electrical signal compatible with the transmitter.
1. 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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109. Elements of Telemetry
The 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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110. Elements of Telemetry
Receiver: 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. Amplification
2. Demodulation:
3. Reverse Signal Conversion
4. De-multiplexing
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111. Elements of Telemetry
Signal 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 Display
3. Digital Storage
4. Data Processing
5. Closed-Loop Control
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112. 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

114. Telemetry Classification Based on Transmission
Medium
1. Wire-Link Telemetry or Wire Telemetry
2. Radio Telemetry or Wireless Telemetry
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Wired Bio Telemetry

116. Wired Telemetry
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117. Elements of Wired Bio-Telemetry(Analog)
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Digital Wired Bio Telemetry

119. Elements of Wired Bio-Telemetry(Digital)
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120. Elements of Wired Digital Bio-Telemetry
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Wireless Bio Telemetry

122. 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 types
1. Short-Range Radio Telemetry
2. Satellite-Radio Telemetry
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123. Elements of Wireless Bio-Telemetry
A typical biotelemetry system comprises:
1. Sensors appropriate for the particular signals to be
monitored
2. Battery-powered, Patient worn transmitters
3. A Radio Antenna and Receiver
4. A display unit capable of concurrently presenting
information from multiple patients
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124. Elements of Basic Wireless Bio-Telemetry
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125. Elements of Wireless Bio-Telemetry
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126. Elements of Wireless Bio-Telemetry
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127. Wireless Bio-telemetry Transmitter
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128. Wireless Bio-telemetry Receiver
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Portable Bio Telemetry

130. Portable Telemetry
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131. Portable Telemetry
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Bio Telemetry Modulation

133. Telemetry Classification Based on Modulation Method
DC Telemetry Systems
1. Direct voltage telemetry system
2. Direct current telemetry system
AC Telemetry Systems
1. Amplitude modulation (AM) telemetry system
2. Frequency modulation (FM) telemetry system
Pulse Telemetry Systems
1. Pulse amplitude modulation (PAM) telemetry system
2. Pulse width modulation (PWM) telemetry system
3. Pulse phase modulation (PPM) telemetry system
4. Pulse frequency modulation (PFM) telemetry system
5. Pulse code modulation (PCM) telemetry system
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134. Direct Current Telemetry
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135. FM Radio Telemetry
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Single Channel Bio Telemetry

137. Single Channel PWM Telemetry
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138. Single Channel PCM Telemetry
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Choice of Carrier frequency

140. 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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