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MOUNT ZOIN ENGINEERING & TECHNOLOGY

CYCLE TEST II

MEDICAL ELECTRONIC-EC1006

Part A

1. Define circulatory system

It is a type of transport system. It helps in supplying the oxygen and digested food to different

parts of our body and removing CO2 from the blood. The heart is the center of the circulatory system.

2.Classify the pacemakers

Fixed rate pacemakers.

Ventricular Synchronous pacemakers

Demand pacemakers

Atrial Synchronous pacemakers

3.Different methods of stimulation

External stimulation, internal stimulation

4.What is a Defibrillator?

A defibrillator is an electronic device that creates a sustained myocardial depolarization of a patient

heart in order to stop ventricular fibrillation or artial fibrillation.

5.What is frequency scaling?

The procedure of converting a cutoff frequency to a new cutoff frequency is called frequency

scaling

6. What is meant by radiopill?

The person swallows the pill and as it passes through the body it gives off information about the

digestive system.

7.Properties of x-rays

X-rays are electromagnetic waves. X-rays are similar to light and sound waves.

X-rays is propagated in straight line

8.What are the characteristics of a DC amplifier?

It may need balanced differential inputs giving a high common mode rejection ratio (CMRR).

It should have extremely good thermal and long term stability

9.What are the types of biotelemetry?

Single channel telemetry system

Multi channel telemetry system

10What are the applications of X-ray?

Skeletal structure

Respiratory organs

Bronchial carcinoma

Circulatory organ

Digestive organs

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Part B

11 a i. Describe the cardi

Pacemaker is an elec

The output of the pacem

In the case of cardiac sta

normal heart rhythm. B

in the body and its elect

In cardiac diseases, whe

pacemaker.

By fixing the artificial ele

The typical ranges of par

1 Pulse rate - 25 - 155 p

2 Pulse width - 0.1 - 2.3

3 Pulse amplitude - 2.5 -4 Battery capacity - 0.44

5 Longevity - 3.5 - 18 ye

6 End-of-life indicator -

7 Weight - 33 - 98 grams

8 Size - 22 - 80 cm3

9 Encapsulization - Silico

ii. Explain the ventricula

Ventricwith short periods of AV

activity.

A single transverse elect

stimulation so, no separ

Electrodes placed in the

If ventricular contractio

does nt complete with t

The electrode is used to

Disadvantages:

1. There may be compet

2. Using the fixed rate p

11.b i.Explain with a ne

The output of the au

with a rms value of abou

A half-wave rectifier rec

The voltage to which C i

A series resistance, Rs, li

An AC voltmeter across

ac pacemaker and explain their importa

t

rical pulse generator for starting and/or

aker is applied either externally to the c

nd still, the use of the pacemaker is tem

t in the case requiring long term pacing,

odes are in direct contact with the hear

e the ventricular rate is too low, it can b

ctronic pacemaker, the above defects in

ameters of the pacemakers available to

lses per minute

illiseconds

10 volts- 3.2 amp-hours

rs

- 10% dropin pulse rate

n rubber, stainless steel, titanium

r synchronous pacemaker

ular synchronised pacemaker can be usblock or bundle block. This pacemaker d

rode placed in the right ventricle senses

te sensing electrode is required.

right ventricules of heart. This electrode

s are absent,then this pacemaker provi

e normal heart activity.

detect the heart rate and it is given to t

ition between the natural heart beats an

cemaker, the heart rate cannot be incre

at diagram, the working principle of D.

totransformer is fed as input to a step-u

t 8000 V.

ifies this high AC voltage to obtain DC v

charged is determined by the autotran

mits the charging current to protect the

he primary is calibrated to indicate the

nce

maintaining the normal heart beat.

hest or internally to the heart muscle.

porary - just long enough to start a

the pacemaker is surgically implanted

.

e increased to normal rate by using

the heart can be eliminated.

ay are,

d only for patientsoes not compete with the normal heart

both R wave as well as delivers the

is used to sene the R-wave.

e the impluse.This type of pacemaker

e amplifier and filter circuit.

d pacemaker beats

ased to match greater physical effort.

. defibrillator.

p transformer to produce high voltage

ltage, which charges the capacitor C.

former in the primary circuit.

components.

nergy stored in the capacitor.

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Five times the RC time constant circuit is required to reach 99% of a full charge-a value it should reach in

10 seconds, which means that the time constant must be less than 2 s.

With the electrodes firmly placed at appropriate positions on the chest, the clinician or technician

discharges the capacitor by momentarily changing the switch S from position 1 to position 2.

Fig:DC defibrillator circuit

ii.Explain with a neat diagram, the working principle of A.C. defibrillator

Although mechanical methods like chest massage for defibrillation have been tried for years,

the most successful method of defibrillation is the application of electric shock to the area of the heart

which makes all the heart muscle fibres enter their refractory period together after which normal heart

action may resume.

One of the earliest forms of an electrical defibrillator is the AC defibrillator, which applies several

cycles of alternating current to the heart from the power line through a step-up transformer.

To achieve defibrillation with internal electrodes placed on the surface of the heart (in open heart

surgery), voltage ranging from 80 to 300V rms is required.

When external electrodes are used on the chest, voltages of twice the value are required.

The transformer must be capable of supplying 4 to 6 amperes current during the stimulus period

Disadvantages:

1. There are many disadvantages in using AC defibrillators.

2. Successive attempts to correct ventricular fibrillation are often required.

3. AC defibrillator cannot be successfully used to correct atrial fibrillation.

12 a. i.Explain the block diagram of a bio-telemetry system. Discuss its design

Bio-telemetry is the measurement of biological parameters over long distance.

For conveying biological information from a living organism and its environment to a different location

where this can be record

Elements of Biotelemetry Systems:

The transducer converts the biological variable into an electrical signal.

The signal conditioner amplifies and modifies this signal for effective transmission.

The transmission line connects the signal input blocks to the read-out device by wire or wireless

means.

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ii. Explain the subcarrie

For a single cha

connected to the electro

The transmitter bro

radio signal and recover

Biosignal from the

and filter at the conditio

Fig: Block diagram of a bio-teleme

biotelemetry system

nnel telemetry system, a miniature batt

des of the patients.

adcast the biopotential to a remote pla

signal for futher processing.

atient is converted into electrical signal

ner. They are transmitted by transmitter

try system

ry operated radio transmitter is

c

e in which the receiver detects the

by the transducer. They are amplifier

antenna.

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12.b Difference between Radiography and fluoroscopy

12.b.ii.Differences between Internal and External Pacemaker

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13.a. What is radiopill? Explain

Radio pill:

Radio pill when swallowed, will travel the GI tract (Gastrointestinal tract) and simultaneously

perform multiparameter in physiological analysis.

After completing its mission it will come out of the human body by normal bowel movement.

The pill is 10mm in diameter and 30mm long weighing around 5gm and records parameters like

temperature, pH, conductivity and dissolved oxygen in real time.

The pill comprises an outer biocompatible capsule encasing micro sensors, a control chip, radiotransmitter and two silver-oxide cells.

INSIDE THE CAPSULE:

The schematic diagram of the microelectronic pill is as shown in figure below. The outer casing of

the pill is made by machining chemically resistant polyetheterketone, which is biocompatible. It is made

up of two halves, which are joined together by screwing.

The pill houses a PCB chip carrier that acts as a common platform for attachment of,

1. sensors,

2. application- specific integrated circuit (ASIC),

3. radio transmitter and

4. batteries

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Radio transmitter:

The size of the transmitter is 8x5x3mm. The transmission range is one meter and the

modulation scheme frequency shift keying has a data rate of 1 kbps. The transmitter is designed tooperate at a transmission frequency of 40.01 MHz at 20C generating a signal of 10KHz bandwidth.

Power consumption:

Two SR44 Ag2O batteries are used, which provide an operating time of more than 40 hours of

the microsystem. The power consumption of the system is around 12.1mW and current consumption is

around 3.9mA at 3.1V supply.

The ASIC and sensor consume 5.3mW corresponding to 1.7mA of current and the free running radio

transmitter consumes 6.8mW at 2.2mA of current.

Range of measurement:

The microsystem can measure,

1. Temperature from 0 to 70C,2. pH from 1 to 13,

3. Dissolved oxygen up to 8.2mg/litre,

4. Conductivity from 0.05 to 10 ms.cm-1( s=siemens).

13.b.How X-rays are generated using X-ray machine

X-rays are produced whenever electrons collide at very high speed with matter and thus suddenly

stopped.

The energy possessed by the electrons appears from the site of the collision as a parcel of energy in the

form of highly penetrating electromagnetic waves (X-rays) of many different wavelengths which

together form a continuous spectrum.

X-rays are produced in a specially constructed glass tube which basically comprises

1. A Source for the production of electrons

2. A Energy source to accelerate the electrons

3. A free electron path

4. A means of focusing the electron beam

5. A device to stop the electrons.

The two types of X-ray tubes are,

1. Stationary mode tube

2. Rotating Anode tube

Stationary Anode tube:An X-ray tube is basically a high vaccum diode in which electrons are generated by thermionic

emission from the filament of the tube. The electron stream is electrostatically focused on the anode by

means of a suitably shaped cathode cup.

The intensity of X-rays depends on the current through the tube. This current can be varied by

varying the heater current, which in turn controls the cathode temperature. The wavelength of the X-

rays depends on the target material and the velocity of the electrons hitting the target. It can be

varied by varying the target voltage of the tube.

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Block Diagram and oper

1.multitap ac line autot

2.X-ray tube filament ci

3.X-ray tube high-volta

4.Timing circuit

14 a. Explain Electro di

Free running multivibrat

The output of free runni

certain pulse width. The

Faradic current and surg

tion of an X-ray machine:

ransformer

rcuit and transformer

e circuit, transformer, bridge rectifier

gnostic stimulator

or is used to set the basic diagnostic sti

ng multivibrator is given to pulse width c

output of pulse width circuit can produc

ed current are modulated by the freque

ulator.

ircuit. Pulse width circuit is used to set

e exponential progressive current.

cy given by free running oscillator.

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Advantage of constant current

Current flow is maintained as a constant one.So, it is not varied during the treatment.

Very small micro voltage between electrodes and skin will not affect the treatment because, constant

current is provided.

14.b.i . Explain the application of biotelemetry

In many situations, it becomes necessary to monitor physiological events from a distance. To

quote a few applications are,

1. Radio frequency transmissions for monitoring the health of astronauts in space.

2. Patient monitoring in an ambulance and in other locations away from the hospital.

3. Collection of medical data from home or office.

4. Patient monitoring, where freedom of movement is desired, such as in obtaining an exercise ECG. (In

this instance, the requirement of trailing wires is cumbersome and dangerous).5. Research on unrestrained and unanesthetized animals in their natural habitat.

6. Use of telephone links for the transmission of ECGs or other medical data.

7. Special internal techniques, such as measuring pH or pressure in the gastrointestinal tract.

8. Isolation of an electrically susceptible patient from power-line operated ECG equipment, to protect

him from accidental shock.

ii. Physiological parameters adaptable to biotelemetry.

Based on the hardware systems, measurements can be applied to two categories:

1. Bioelectrical Parameters, such as ECG, EEG and EMG.

2. Physiological variables that require transducers such as blood pressure, gastrointestinal pressure,

blood flow and temperatures.

Bioelectric Parameters: (such as ECG, EMG and EEG)

The signal is obtained directly in electrical form. One example is ECG telemetry - the transmission of

ECGs from an ambulance or site of emergency to a hospital. A cardiologist at the hospital can

immediately interpret the ECG, instruct the trained rescue team in their emergency resuscitation

procedures and arrange for any special treatment that may be necessary upon the patients arrival at

the hospital. In this application, the telemetry to the hospital is supplemented by two-way voice

communication.

Physiological variables:

The physiological parameters are measured as a variation of resistance, capacitance or

inductance. The differential signal obtained from these variations can be calibrated to represent

pressure flow, temperature and so on.

15.a Write briefly about the power sources used for implantable type of pacemaker

Mercury cell

The life time of mercury cell is 2-3 year.

Lithium cell

It is one of the mostly widely used. It has the life span of more than 5 year.

Rechargeable battery

Rechargeable battery is not widely used.

Nuclear cell

High voltage nuclear cell

Low voltage nuclear cell

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Nuclear cell

A fuel cell is electrochemical device, which directly converts the chemical energy of a fuel oxidation

reaction into electrical energy.

15.b With a block diagram, explain the instrumentation system for radioisotope procedures

The pulses from the photomultiplier tube are amplified and shortened before they are

passed to through the pulse height analyzer. A timer and gate allow the pulses that occur in a set time

interval to be counted by means of a scaler (decimal counter with readout).

A rate meter (frequency meter) shows the rate of the pulses. Based on

the reading of the rate meter, the detector can be aimed towards the location of maximal radioactivity

and the pulse-height analyzer can be set in the range where it passes all the pulses from the particular

isotope used.

In an automatic system, for the measurement of radioactivity in "in vitro" samples an automatic

sample changer arm (right) selects test tube containing the samples from a carousel and drops theminto a counting well.

The number of radioactive disintegrations measured over a preselected time interval is printed

out on the printer.

The principle of the collimated scintillation detector can be used to visualize the spatial

distribution of radioisotopes in a body organ.

In a radioisotope scanner, the detector is slowly moved over the area to be examined in a zigzag

fashion. A recording mechanism attached to the mounting arm of the detector produces a plot of the

distribution of the radioactivity.

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