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Multiple choice question for engineering

Set 1

1. _____________ instrument is used for recording the electrical activity of the brain.
a) ECG
b) PCG
c) EEG
d) EMG

View Answer

Answer: c [Reason:] EEG, describing the general function of the brain activity, is the superimposed wave of neuron potentials operating in a non-synchronized manner in the physical sense. Electroencephalograph is an instrument for recording the electrical activity of the brain, by suitably placing surface electrodes on the scalp.

2. EEG electrodes are smaller in size than ECG electrodes.
a) True
b) False

View Answer

Answer: a [Reason:] EEG electrodes are smaller in size than ECG electrodes. Several types of electrodes may be used to record EEG. These include: Peel and Stick electrodes, Silver plated cup electrodes and Needle electrodes.

3. Which of the following is the superimposed wave of neuron potentials operating in a non-synchrronized manner in physical sense ?
a) EEG
b) ECG
c) VCG
d) PCG

View Answer

Answer: a [Reason:] Electroencephalograph is an instrument for recording the electrical activity of the brain, by suitably placing surface electrodes on the scalp. EEG, describing the general function of the brain activity, is the superimposed wave of neuron potentials operating in a non-synchronized manner in the physical sense.

4. ______________ material is used to improve electrical contact in electrodes with the skin.
a) Silver Tungsten
b) Copper Tungsten
c) Electrode jelly
d) Silver Graphite

View Answer

Answer: c [Reason:] If the electrodes are intended to be used under the skin of the scalp, needle electrodes are used. Electrode jelly or paste is used to improve the electrical contact. They offer the advantage of reducing movement artefacts.

5. Which among the following electrode gives high skin impedance as compared to ECG?
a) VCG
b) EEG
c) EMG
d) PCG

View Answer

Answer: b [Reason:] EEG electrodes give high skin contact impedance as compared to ECG electrodes. Good electrode impedance should be generally below 5 kilohms. Impedance between a pair of electrodes must also be balanced or the difference between them should be less than 2 kilohms.

6. Which of the following component is generally designed to have a very high value of input impedance to take care of high electrode impedance?
a) Montages
b) Filters
c) Electrodes
d) Preamplifiers

View Answer

Answer: c [Reason:] EEG preamplifiers are generally designed to have a very high value of input impedance to take care of high electrode impedance.Good electrode impedance should be generally below 5 kilohms. Impedance between a pair of electrodes must also be balanced or the difference between them should be less than 2 kilohms.

7. What is the recording called in which voltage difference between an active electrode on scalp with respect to reference electrode at ear lobe or any other part of body is recorded?
a) Unipolar
b) Bipolar
c) Monopolar
d) Nonpolar

View Answer

Answer: c [Reason:] This type of recording is called ‘monopolar’ recording. EEG may be recorded by picking up the voltage difference between an active electrode on the scalp with respect to a reference electrode on the ear lobe or any other part of the body.

8.WHich of the following is employed for bipolar recording done?
a) Uni Channel EEG
b) Omni channel EEG
c) Non Channel EEG
d) Multi channel EEG

View Answer

Answer: d [Reason:] Such recordings are done with multi-channel electroencephalographs. ‘bipolar’ recording is more popular wherein the voltage difference between two scalp electrodes is recorded.

9.EEG signals picked up by surface electrodes are usually larger as compared to ECG.
a) True
b) False

View Answer

Answer: b [Reason:] They may be several hundred microvolts, but 50 microvolts peak-to-peak is the mosttypical. Yes, EEG signals picked up by the surface electrodes are usually small as compared with the ECG signals.

10. A pattern of electrodes on the head and the channels they are connected to is called a
montage. Montages are always ___________
a) inverse
b) random
c) symmetrical
d) asymmetrical

View Answer

Answer: c [Reason:] Montages are always symmetrical. A pattern of electrodes on the head and the channels they are connected to is called a montage. The reference electrode is generally placed on a nonactive site such as the forehead or earlobe.

11. Reference electrode for recording EEG is placed on __________
a) forehead
b) cervical
c) nasal
d) facial

View Answer

Answer: a [Reason:] The reference electrode is generally placed on a nonactive site such as the forehead or earlobe. A pattern of electrodes on the head and the channels they are connected to is called a montage. Montages are always symmetrical.

12. The typical value of calibration signal is ________
a) 10 uV/cm
b) 70 uV/cm
c) 50 uV/cm
d) 30 uV/cm

View Answer

Answer: c [Reason:] A typical value of the calibration signal is 50 uV/cm. A calibrating signal is used for controlling and documenting the sensitivity of the amplifier channels. This supplies a voltage step of adequate amplitude to the input of the channels.

13. Preamplifiers used in electroencephalograph have low gain and high noise characteristics for EEG.
a) True
b) False

View Answer

Answer: b [Reason:] It is False. Preamplifier used in electroencephalographs must have high gain and low noise characteristics because the EEG potentials are small in amplitude. In addition, the amplifier must have very high common-mode rejection to minimise stray interference signals from power lines and other electrical equipments.

14. At what frequency is the notch filter in EEG machines sharply tuned to eliminate mains frequency interference?
a) 60
b) 90
c) 10
d) 70

View Answer

Answer: a [Reason:] EEG machines have a notch filter sharply tuned at 60 Hz so as to eliminate mains frequency interference. The use of notch filters should preferably be restricted to exceptional circumstances when all other methods of eliminating interference have been found to be ineffective. These however have the undesirable property of ‘ringing’ i.e. they produce a damped oscillatory response to a square wave calibration waveform or a muscle potential.

15. ______________ is typical frequency range of standard EEG machines.
a) 70 to 140 Hz
b) 0.1 to 70 Hz
c) 0.05 to 0.1 Hz
d) 0.025 to 0.05 Hz

View Answer

Answer: b [Reason:] The typical frequency range of standard EEG machines is from 0.1 Hz to 70 Hz, though newer machines allow the detection and filtering of frequencies up to several hundred Hertz. This may be of importance in some intracranial recordings.

Set 2

1. What is the principle behind Doppler velocimetry working?
a) amplitude measurement of fiber optic sensor
b) frequency measurement of fiber optic sensor
c) time shift measurement of fiber optic sensor
d) phase measurement of fiber optic sensor

View Answer

Answer: b [Reason:] Doppler velocimetry works on the principle of frequency measurement of fiber optic sensor. The moving red blood cells scatter the light and produce a Doppler frequency shift because of their movement.In this method, light from a laser, normally helium/neon, is sent via a fibre onto the skin surface.

2. Which of the follong is the principle behind Fluoroptic temperature sensors working?
a) optical fiber
b) thermistor
c) thermocouple
d) rtd

View Answer

Answer: a [Reason:] They contain a rare earth phosphor which is illuminated by a white light along a short length of large core optical fibre. Fluoroptic temperature sensors work on the principle of optical fiber sensors. The light excites the phosphor which emits a number of lines. By using filters, two of these lines at 540 and 630 nm are selected, and the ratio of their intensities is a single valued function of the temperature of the phosphor.

3. Monopolar needle electrode have a coating of______________ material over the stainless steel wires which are bare only at the tips.
a) carbon
b) calcium
c) teflon
d) sodium

View Answer

Answer: c [Reason:] The wire is bare only at the tip. The monopolar needle electrode consists of a teflon coated stainless steel wire. It is found that after the needle has been used a number of times, the teflon coating will recede, increasing the tip area. The needle should be discarded when this happens.

4. Which of the following sensor is used for Endoscopic imaging ?
a) thermal sensors
b) optic fiber sensors
c) chemical sensors
d) pressure sensors

View Answer

Answer: b [Reason:] Optical fibre sensors are non-electrical and hence are free from electrical interference usually associated with electronically based sensors. Optic sensors are used for endoscopic imaging. They are suitable for telemetry applications as bulk of the instrumentation can be at a reasonable distance from the patient.

5. Which of the following component converts biochemical events into measurable signals?
a) amplifier
b) opamp
c) rectifier
d) transducer

View Answer

Answer: d [Reason:] Transducers convert biochemical events into measurable signals. They provide the means for detecting the biochemical changes inside the body. Particularly biosensors are employed for this purpose.

6. Which of the following is used to determine the biological response of the biosensor ?
a) artificial membrane
b) chemical membrane
c) physio-chemical membrane
d) biocatalytic membrane

View Answer

Answer: d [Reason:] The biocatalytic membrane accomplishes the conversion of reactant to product. The product of the reaction diffuses to the transducer.The biological response of the biosensor is determined by biocatalytic membrane. This then causes the electrical response.

7. What is the working principle behind Home blood glucose sensor ?
a) electro-physiological
b) electrochemical
c) chemical
d) physio-chemical

View Answer

Answer: b [Reason:] Home blood glucose detection sensor works on the principle of electrochemical. The biosensor in this instrument relies upon enzymes that recognise and catalyze reactions of glucose with the generation of redox – active species that are detected electrochemically.

8. ____________ is a wireless ECG acquiring system.
a) pregelled disposable electrodes
b) smart pad
c) pasteless electrodes
d) limb electrodes

View Answer

Answer: b [Reason:] Smart pad is a system that displays a patients electrocardiogram signals without adhesive pads, wires or active intervention from a clinician. The selected electrodes are used to provide a differential 3 lead measurement of the patient’s ECG, which is then transmitted wirelessly and displayed on a laptop computer. The system automatically selects three electrodes from an array of Cu/Ni fabric based electrodes patterned on a thin pad on which the patient lies.

9. Home blood glucose measurement devices measure the glucose level through invasive method.
a) True
b) False

View Answer

Answer: a [Reason:] There is a small needle at the tip of the machine that pierces the skin to take blood sample. Home blood glucose measurement devices measure the glucose level through invasive method. This blood is then undergoes electrochemical reactions and the glucose level is determined.

10. Blood glucose level measurement device uses a biosensor works on the principle of _____________
a) electromechanical
b) electrochemical
c) electrothermal
d) electroresistive

View Answer

Answer: b [Reason:] The biosensor in this instrument relies upon enzymes that recognise and catalyze reactions of glucose with the generation of redox – active species that are detected electrochemically.Home blood glucose detection sensor works on the principle of electrochemical.

Set 3

1. _________ instrument is used for recording the electrical activity of the muscles.
a) ECG
b) EMG
c) PCG
d) EEG

View Answer

Answer: b [Reason:] Electromyograph is an instrument used for recording the electrical activity of the muscles to determine whether the muscle is contracting or not; or for displaying on the CRO and loudspeaker the action potentials spontaneously present in a muscle or those induced by voluntary contractions as a means of detecting the nature and location of motor unit lesions; or for recording the electrical activity evoked in a muscle by the stimulation of its nerve.

2. EMG cannot be recorded by using surface electrodes.
a) True
b) False

View Answer

Answer: b [Reason:] It is False. EMG is usually recorded by using surface electrodes because the surface electrodes may be disposable, adhesive types or the ones which can be used repeatedly.

3.Which of the following signal is used to myoelectric prosthetic devices?
a) EEG
b) EMG
c) ECG
d) VCG

View Answer

Answer: b [Reason:] EMG measurements are also important for the myoelectric control of prosthetic devices (artificial limbs). This is the most demanding requirement from an EMG since on it depends the working of the prosthetic device. This use involves picking up EMG signals from the muscles at the terminated nerve endings of the remaining limb and using the signals to activate a mechanical arm.

4. _________ is the most common and convenient source of light.
a) Neon-xenon arc
b) Xenon-mercury arc
c) Tungsten lamp
d) Hydrogen discharge lamp

View Answer

Answer: c [Reason:] The most common and convenient source of light is the tungsten lamp. This lamp consists of a tungsten filament enclosed in a glass envelope. It is cheap, intense and reliable. A major portion of the energy emitted by a tungsten lamp is in the visible region and only about 15 to 20% is in the infrared region.

5. Which of the following factor determines the amplitude of EMG signal ?
a) Respiration
b) Ventricular Volume
c) Blood Resistivity
d) Position of electrode

View Answer

Answer: d [Reason:] The amplitude of the EMG signals depends upon various factors, e.g. the type and placement of electrodes used and the degree of muscular exertions. The needle electrode in contact with a single muscle fibre will pick up spike type voltages whereas a surface electrode picks up many overlapping spikes and therefore produces an average voltage effect.

6. EMG signals range from ______________
a) 0.1 to 0.5 mV
b) 0.050 to 0.1 mV
c) 0.5 to 1 mV
d) 0.025 to 0.050 mV

View Answer

Answer: a [Reason:] A typical EMG signal ranges from 0.1 to 0.5 mV. They may contain frequency components extending up to 10 kHz.Such high frequency signals cannot be recorded on the conventional pen recorders and therefore, they are usually displayed on the CRT screen.

7. Modern day calorimeters and spectrophotmetry instruments use ________ light source.
a) Tungsten-halogen lamp
b) Xenon-mercury lamp
c) Deuterium discharge lamp
d) Mercury arc

View Answer

Answer: d [Reason:] Modern instruments use a tungsten-halogen light source, which has a higher intensity output than the normal tungsten lamp in the change over region of 320–380 nm used in colorimetry and spectrophotometry. It also has a larger life and does not suffer from blackening of the bulb glass envelope.

7. Which of the following from the options is included in the system to facilitate playback and study of EMG sound waveforms at a later convenient time?
a) Tape Recorder
b) Preamplifier
c) Oscilloscope
d) Ground Electrode

View Answer

Answer: a [Reason:] The waveform can also be photographed from the CRT screen by using a synchronized camera. The tape recorder is included in the system to facilitate playback and study of the EMG sound waveforms at a later convenient time.

8. ____________ is necessary for providing a common reference for measurement?
a) active electrode
b) ground electrode
c) tape recorder
d) oscilloscope

View Answer

Answer: b [Reason:] A ground electrode is necessary for providing a common reference for measurement. The signal can then be amplified and displayed on the screen of a cathode ray tube. It is also applied to an audio amplifier connected to a loudspeaker. These electrodes pick up the potentials produced by the contracting muscle fibres.

9. Which among the following are optical systems, which provide better isolation of spectral energy than the pptical filters.
a) Spectromators
b) Monochromators
c) Baromators
d) Tocochromators

View Answer

Answer: b [Reason:] Monochromators are optical systems, which provide better isolation of spectral energy than the optical filters, and are therefore preferred where it is required to isolate narrow bands of radiant energy. Monochromators usually incorporate a small glass of quartz prism or a diffraction grating system as the dispersing media.

9. _______________ is not an arrhythmic condition.
a) Cardiographic beat
b) Bradycardia
c) Ectopic beat
d) Dropped beat

View Answer

Answer: a [Reason:] These are bradycardia, tachycardia, dropped beat and premature beat. The analyzer part in automatic scanning of ambulatory records look for four arrhythmic conditions. A threshold control is associated with each of these and when the appropriate threshold is exceeded, an alarm condition is generated.

10. CMRR of preamplifier upto 5 Khz should be _____________
a) 10 dB
b) greater than 90 dB
c) less than 90 dB
d) 30 dB

View Answer

Answer: b [Reason:] The common-mode rejection should be greater than 90 dB up to 5 kHz. The main amplifier has controls for gain adjustment from 5 mV/div to 10 mV/div for selecting the sensitivity most appropriate to the incoming signal from the patient.A calibrating square wave signal of 100 mV (peak-to-peak) at a frequency of 100 Hz is usually available.

11. Holter Cardiography is ambulatory monitoring of ECG signal.
a) True
b) False

View Answer

Answer: a [Reason:] Modern EMG machines are PC based available both in console as well as laptop models as they provide full colour waveform display, automatic cursors for marking and making measurements and a keyboard for access to convenient and important test controls. Ambulatory monitoring of ECG is called ‘Holter Cardiography’, after Dr Norman Holter who introduced this concept in 1962. A Holter monitor is a type of ambulatory electrocardiography device, a portable device for cardiac monitoring (the monitoring of the electrical activity of the cardiovascular system) for at least 24 hours (often for two weeks at a time).

12. EMG instrument is useful for making study of ___________
a) cardiovascular function
b) neuromuscular function
c) nervous function
d) Immune function

View Answer

Answer: b [Reason:] The instrument is useful for making a study of several aspects of neuromuscular function, neuromuscular condition, extent of nerve lesion, reflex responses, etc.

13. Which of the following instrument is used for making study of reflex responses?
a) EEG
b) ECG
c) VCG
d) EMG

View Answer

Answer: d [Reason:] The instrument is useful for making a study of several aspects of neuromuscular function, neuromuscular condition, extent of nerve lesion, reflex responses, etc.

14. _____________ provides an excellent review of ambulatory cardiac event recorders.
a) Alfonso
b) Benz
c) Handelsman
d) Friesen

View Answer

Answer: b [Reason:] An excellent review of ambulatory cardiac event recorders is provided by Benz in 1999. The major advantage of these devices compared with a traditional Holter monitor is that they are small, allow ECG monitoring for longer time periods, and can provide nearly real time data analysis when the patient transmits a recording in proximity to the symptomatic event.

15. ________ CPU has overall system control responsibility.
a) Control
b) Acquisition
c) Control and timing
d) Acquisition and display

View Answer

Answer: c [Reason:] It also handles individuals functions such as keyboard and direct writer interface, tape deck control, timing data processing, and arrhythmia count totalizing via a high speed interrupt system. The control and timing CPU has overall system control responsibility.

Set 4

1. Blood flow detectors based on Doppler shift start detecting foetal pulses as early as in which week of pregnancy?
a) tenth
b) eleventh
c) twelfth
d) ninth

View Answer

Answer: b [Reason:] Blood flow detectors based on ultrasonic Doppler shift can detect foetal pulse as early as the tenth week of pregnancy and in nearly all cases by the twelfth week. At about 20 weeks it is possible to detect multiple pregnancies especially if two instruments are used together and the pulse rates compared. Intrauterine death of the foetus can also be diagnosed.

2. When it is possible to detect multiple pregnancies?
a) 10th week
b) 12th week
c) 15th week
d) 20th week

View Answer

Answer: d [Reason:] Blood flow detectors based on ultrasonic Doppler shift can detect foetal pulse as early as the tenth week of pregnancy and in nearly all cases by the twelfth week. At about 20 weeks it is possible to detect multiple pregnancies especially if two instruments are used together and the pulse rates compared. Intrauterine death of the foetus can also be diagnosed.

3. Which of the following is the most reliable method for detecting FHR pattern?
a) Abdominal foetal electrocardiogram
b) Foetal phonocardiogram
c) Ultrasound technique
d) Foetal ECG with scalp electrode

View Answer

Answer: c [Reason:] We can hear the signal through a loudspeaker with a scarce chance of failing to recognize any beat, but a simple electronic circuit may fail to trigger from this signal. Still, the ultrasound Doppler shift method is more practical and easy to use during labour. It is currently the most reliable method for detecting the FHR pattern that is interpretable.

4. Signal processing for FHR determination can be based either on detecting the foetal heart valve motion or on detecting the heart wall motion in Abdominal foetal electrocardiogram technique.
a) True
b) False

View Answer

Answer: b [Reason:] False, Signal processing for FHR determination can be based either on detecting the foetal heart valve motion or on detecting the heart wall motion in Ultrasound technique as The heart valve motion detection technique is based on the distinct ultrasound frequency shift produced by the fast opening and closing of the heart valves. The technique, however, requires that the ultrasound beam must be directed against the relatively small heart valves involving a longer search period and frequent repositioning of the transducer.Therefore, it is not preferred for continuous monitoring applications.

5. What is maximum ultrasound intensity of narrow beam transducer?
a) 15 mW/cm2
b) 20 mW/cm2
c) 25 mW/cm2
d) 30 mW/cm2

View Answer

Answer: c [Reason:] The narrow beam transducer uses a single ultrasound transmitter/receiver piezo-electric crystal pair. The maximum ultrasound intensity is generally kept below 25 mW/cm2. The typical transducer diameter is 25 mm. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.

6. What is the diameter of narrow beam transducer?
a) 15 mm
b) 20 mm
c) 25 mm
d) 30 mm

View Answer

Answer: c [Reason:] The narrow beam transducer uses a single ultrasound transmitter/receiver piezo-electric crystal pair. The maximum ultrasound intensity is generally kept below 25 mW/cm2. The typical transducer diameter is 25 mm. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.

7. What is used to detect foetal heart movements in broad beam transducer?
a) Quartz crystal
b) Piezo electric crystal
c) Topaz crystal
d) Berlinite crystal

View Answer

Answer: b [Reason:] The broad beam transducers are available in many configurations. The transducers comprise a number of piezo-electric crystals mounted in such a way as to be able to detect foetal heart movements over a wider area.

8. The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination.
a) True
b) False

View Answer

Answer: a [Reason:] True, The narrow beam transducer is very sensitive and produces a good trigger signal for instantaneous heart rate determination because it takes time to detect a good signal and, therefore, frequent transducer repositioning is necessary.

9. Which of the following transducer is used to detect foetal heart movements over a wider area?
a) piezo-electric
b) ultrasonic
c) array
d) pressure

View Answer

Answer: a [Reason:] The broad beam transducers are available in many configurations. The transducers comprise a number of piezo-electric crystals mounted in such a way as to be able to detect foetal heart movements over a wider area.

10. Which transducer is arranged in the shape of a clover leaf so that it provides a large area of illumination?
a) piezo-electric
b) ultrasonic
c) array
d) pressure

View Answer

Answer: b [Reason:] The ultrasonic transducer is arranged in the shape of a clover-leaf so that it provides a large area of ultrasonic illumination which allows the monitoring considerable lateral and descending foetal motion before requiring repositioning. The transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.

11. The array transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.
a) True
b) False

View Answer

Answer: b [Reason:] False, The ultrasonic transducer is arranged in the shape of a clover-leaf so that it provides a large area of ultrasonic illumination which allows the monitoring considerable lateral and descending foetal motion before requiring repositioning. The ultrasonic transducer housing is flexible to permit it to follow the contour of the abdomen regardless of shape changes with contractions.

12. At what angle divergent beam is transmitted by crystal in array transducer?
a) 10°
b) 20°
c) 30°
d) 40°

View Answer

Answer: d [Reason:] An alternative arrangement is the array transducer which has one transmitter and six peripheral ceramic receiving crystals. The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter.

13. The transmitting crystal emits 40° divergent beam so that the beam covers an area of approximately _____ cm diameter.
a) 10
b) 20
c) 30
d) 40

View Answer

Answer: a [Reason:] An alternative arrangement is the array transducer which has one transmitter and six peripheral ceramic receiving crystals. The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter.

14. What is diameter of array transducer?
a) 2
b) 4
c) 6
d) 8

View Answer

Answer: c [Reason:] The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter. This construction ensures continuous recording of the foetal heart activity without the need to reposition the transducer which is otherwise necessitated due to normal foetal movement. The transducer has a diameter of 6 cm and can be held in place either by a simple buckle or a stretch belt.

15. The array transducer can be held in place by a simple buckle.
a) True
b) False

View Answer

Answer: a [Reason:] True,The transmitting crystal emits a 40° divergent beam so that at 10 cm from the skin surface the beam covers an area of approximately 10 cm diameter. This construction ensures continuous recording of the foetal heart activity without the need to reposition the transducer which is otherwise necessitated due to normal foetal movement. The transducer has a diameter of 6 cm and can be held in place either by a simple buckle or a stretch belt.

Set 5

1. Which of the following instrument is used to measure blood flow in skin?
a) NMR Blood Flowmeter
b) Ultrasonic Blood Flowmeter
c) Electromagnetic Blood Flowmeter
d) Laser Doppler Blood Flowmeter

View Answer

Answer: d [Reason:] A system utilizing the Doppler-shift of monochromatic laser light to measure blood flow in skin is described by Watkins and Holloway (1978). When a laser beam is directed towards the tissue under study, absorption and scattering takes place. Radiation scattered in movable structures, such as red cells, is shifted in frequency due to the Doppler effect, while radiation scattered in nonmoving soft tissue is unshifted in frequency.

2. What is the effective radiation penetration depth in soft tissue?
a) 1 mm
b) 2 mm
c) 3 mm
d) 4 mm

View Answer

Answer: a [Reason:] The effective radiation penetration depth is approximately 1 mm in soft tissue and scattering and absorption take place mostly in the papilla region and the underlying corium—two dermal layers containing the capillary network of the skin.

3. What is power of laser light used in Laser Doppler Blood flowmeter?
a) 2 mW
b) 3 mW
c) 4 mW
d) 5 mW

View Answer

Answer: d [Reason:] In principle, light from a low power (5 mW) He–Ne laser is coupled into a quartz fibre and transmitted to the skin. The light is reflected from both the non-moving tissues (reference beam) and moving red blood cells (Doppler-shifted beam). The two beams are received by a plastic fibre and transmitted back to a photo-diode where optical heterodyning takes place.

4. Which laser is used in Laser dopller blood flowmeter?
a) Nd-YAG
b) Argon
c) He-Ne
d) CO2

View Answer

Answer: c [Reason:] In principle, light from a low power (5 mW) He–Ne laser is coupled into a quartz fibre and transmitted to the skin. The light is reflected from both the non-moving tissues (reference beam) and moving red blood cells (Doppler-shifted beam). The two beams are received by a plastic fibre and transmitted back to a photo-diode where optical heterodyning takes place.

5. What is used to receive beams of light?
a) Plastic fibre
b) Photo diode
c) He-Ne Laser
d) CO2 Laser

View Answer

Answer: a [Reason:] In principle, light from a low power (5 mW) He–Ne laser is coupled into a quartz fibre and transmitted to the skin. The light is reflected from both the non-moving tissues (reference beam) and moving red blood cells (Doppler-shifted beam). The two beams are received by a plastic fibre and transmitted back to a photo-diode where optical heterodyning takes place.

6. Where optical heterodyning takes place in Laser Doppler Blood Flowmeter?
a) Plastic fibre
b) Photo diode
c) He-Ne Laser
d) CO2 Laser

View Answer

Answer: b [Reason:] In principle, light from a low power (5 mW) He–Ne laser is coupled into a quartz fibre and transmitted to the skin. The light is reflected from both the non-moving tissues (reference beam) and moving red blood cells (Doppler-shifted beam). The two beams are received by a plastic fibre and transmitted back to a photo-diode where optical heterodyning takes place.

7. The laser output is coupled into the fibre using a converging lens.
a) True
b) False

View Answer

Answer: a [Reason:] True, The He–Ne laser operating at 632.8 nm wavelength is used. The laser output is coupled into the fibre using a converging lens, which results in an increased power density at the skin surface and thus enables the detection of flow in the more deeply seated veins and arteries.

8. What is operating wavelength of He-Ne laser?
a) 610.8 nm
b) 622.6 nm
c) 632.8 nm
d) 650 nm

View Answer

Answer: c [Reason:] The He–Ne laser operating at 632.8 nm wavelength is used. The laser output is coupled into the fibre using a converging lens, which results in an increased power density at the skin surface and thus enables the detection of flow in the more deeply seated veins and arteries.

9. What functions as square law device and gives out current?
a) Plastic fibre
b) Photodetector
c) He-Ne Laser
d) CO2 Laser

View Answer

Answer: b [Reason:] The photodetector functions as a square law device and gives out current, which is proportional to the intensity of the incident light and, therefore, to the frequency of beating of the shifted and unshifted signals. The light falling on the photodetector is an optically mixed signal involving a Doppler-shifted signal back scattered from the moving red blood cells with the ‘reference’ signal reflected from the non-moving skin surface.

10. Which technique seems to offer several advantages like light reproducibility and sensitivity?
a) NMR
b) Laser Doppler
c) Electromagnetic
d) Ultrasonic

View Answer

Answer: b [Reason:] Laser Doppler flowmetry is a non-invasive technique and seems to offer several advantages like light reproducibility and sensitivity. However, its disadvantages like poor selectivity, base line instability and restriction in site of measurement are still limiting factors in its successful clinical utilization.