Biomedical Instrumentation Questions and Answers – Recording System

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This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Recording System”.

1. How are foetal heart sounds picked up from the maternal abdomen?
a) Piezoelectric device
b) Sensitive Microphone
c) Crystal microphone
d) Dynamic microphone
View Answer

Answer: b
Explanation: Foetal heart sounds can be picked up from the maternal abdomen by a sensitive microphone. The heart sounds in the form of mechanical vibrations have to pass through tissue structure and the signals picked up are rather weak because of distance effects and the small size of foetal heart valves.
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2. Crystal microphone is used for picking _______ signals.
a) cardiac
b) brain
c) phono
d) muscles
View Answer

Answer: c
Explanation: To pick up the heart sounds, it is essential that the transducer is properly placed and its impedance carefully matched. A crystal microphone is used for picking up phono signals. The phono transducer signals are amplified by a low noise preamplifier and fed to a bandpass filter which rejects all frequencies outside the 70 to 110 Hz range.

3. Bandpass filter used in foetal phonocardiogram rejects all frequencies outside the ________ Hz range.
a) 0-40
b) 40-80
c) 70-110
d) 110-150
View Answer

Answer: c
Explanation: To pick up the heart sounds, it is essential that the transducer be properly placed and its impedance carefully matched. A crystal microphone is used for picking up phono signals. The phono transducer signals are amplified by a low noise preamplifier and fed to a bandpass filter which rejects all frequencies outside the 70 to 110 Hz range.
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4. The preamplifier is incorporated in the transducer housing to maximize interference signals being picked up.
a) True
b) False
View Answer

Answer: b
Explanation: The preamplifier is incorporated in the transducer housing to minimize interference signals being picked up. Much of the random noise is eliminated during this process and the record on paper after this stage is called foetal phonocardiograph.

5. How many sounds are produced from the normal foetal heart action?
a) 1
b) 2
c) 3
d) 4
View Answer

Answer: b
Explanation: From the normal foetal heart action, generally two sounds are produced corresponding to the contraction and relaxation of the heart muscles. These two bursts of heart sounds are mixed up with unwanted signals which may succeed in passing through the filters.
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6. What is the fixed pulse width of the pulse after process of one-shot circuit?
a) 110 ms
b) 170 ms
c) 230 ms
d) 280 ms
View Answer

Answer: c
Explanation: After peak detection, the processed pulses operate a one-shot circuit which gives a fixed pulse width of 230 ms. The output of one-shot triggers a variable pulse width multi-vibrator which adds and gives either 43 or 116 ms time depending on the heart rate. The pulse width at the output will be either 230 + 43 = 273 ms or 230 + 116 = 346 ms.

7. What is used to detect heart frequency in foetal phonocardiograph?
a) 230 ms one shot
b) 400 ms one shot
c) 20 ms one shot
d) 440 ms one shot
View Answer

Answer: b
Explanation: To detect the heart frequency, the 400 ms one-shot is used. If the period duration is greater than 400 ms, the one-shot will deliver a pulse. The negative slope of this pulse is used to trigger the 20 ms one-shot. These 20 ms pulses are integrated by the integrator and the output of this integrator is compared with a fixed voltage -V.
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8. If the period duration is lesser than 400 ms, the one-shot will deliver a pulse.
a) True
b) False
View Answer

Answer: b
Explanation: False, to detect the heart frequency, the 400 ms one-shot is used. If the period duration is greater than 400 ms, the one-shot will deliver a pulse. The negative slope of this pulse is used to trigger the 20 ms one-shot. These 20 ms pulses are integrated by the integrator and the output of this integrator is compared with a fixed voltage -V.

9. What is used to delay the change in the time constant in foetal phonocardiograph?
a) Preamplifier
b) Notch Filter
c) Integrator
d) Band Pass Filter
View Answer

Answer: c
Explanation: The integrator is used to delay the change in the time constant and to make sure that a change of on-time takes place only if several (3 to 4) heart beats with the longer period duration (below 150 bpm) are present.
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10. No output pulse will occur when the period between two pulses is less than _____ ms.
a) 230
b) 20
c) 400
d) 440
View Answer

Answer: c
Explanation: No output pulse will occur if the period between two pulses is less than 400 ms. The 20 ms pulses are, therefore, not generated and the integrator discharges slowly from the negative output voltage to a positive output voltage. If the output of the integrator (6) is less negative than-V, the output of the comparator (7) will become negative.

11. Ultrasound provides basically clearer signal than does phonocardiography.
a) True
b) False
View Answer

Answer: b
Explanation: False, Phonocardiography provides a basically cleaner signal than does ultrasound, thus allowing a greater chance of detecting a smooth baseline FHR. Unfortunately, phonocardiography is more susceptible to artefacts introduced from ambient noise, patient movement or other intra-abdominal sounds.

12. Which of the following instrument makes use of the Doppler shift principle?
a) Abdominal Foetal Electrocardiogram
b) Foetal Phonocardiogram
c) Foetus blood flow detector
d) Foetal ECG with scalp electrode
View Answer

Answer: c
Explanation: An important clinical instrument for obstetric applications which makes use of the Doppler shift principle is the foetus blood flow detector. The technique is extended to derive an integrated rate of the foetus heart from blood flow signals and to display it on a suitable display system.

13. Which technique is used to derive an integrated rate of the foetus heart from blood flow signals and to display it on a suitable display system?
a) Abdominal Foetal Electrocardiogram
b) Foetal Phonocardiogram
c) Ultrasound
d) Foetal ECG with scalp electrode
View Answer

Answer: c
Explanation: An important clinical instrument for obstetric applications which makes use of the Doppler shift principle is the foetus blood flow detector. The ultrasound technique is extended to derive an integrated rate of the foetus heart from blood flow signals and to display it on a suitable display system.

14. What is ultrasonic frequency employed for obstetric studies?
a) 0.5 to 1 MHz
b) 1 to 1.5 MHz
c) 1.5 to 2 MHz
d) 2 to 2.5 MHz
View Answer

Answer: d
Explanation: For obstetric studies, ultrasonic frequency of about 2 to 2.5 MHz is usually employed, whereas in the study of blood flow in arteries and superficial blood vessels frequencies around 5–10 MHz are preferred. The level of ultrasonic energy transmitted into the body is generally kept between 10–15 mW/cm2.

15. What is range of ultrasonic energy transmitted into the body?
a) 0-5 mW/cm2
b) 5-10 mW/cm2
c) 10-15 mW/cm2
d) 15-20 mW/cm2
View Answer

Answer: c
Explanation: For obstetric studies, ultrasonic frequency of about 2 to 2.5 MHz is usually employed, whereas in the study of blood flow in arteries and superficial blood vessels frequencies around 5–10 MHz are preferred. The level of ultrasonic energy transmitted into the body is generally kept between 10–15 mW/cm2.

Sanfoundry Global Education & Learning Series – Biomedical Instrumentation.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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