This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Measurement of Heart Rate”.
1. Which of the following instrument is used for recording the electrical activity of the brain?
a) ECG
b) EMG
c) PCG
d) EEG
View Answer
Explanation: 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.
2. EEG electrodes are larger in size than ECG electrodes.
a) True
b) False
View Answer
Explanation: Several types of electrodes may be used to record EEG. These include: Peel and Stick electrodes, Silver plated cup electrodes and Needle electrodes. EEG electrodes are smaller in size than ECG electrodes.
3. _______ is the superimposed wave of neuron potentials operating in a non-synchrronized manner in a physical sense.
a) VCG
b) ECG
c) EEG
d) PCG
View Answer
Explanation: 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. Which of the following is material is used to improve electrical contact?
a) Silver Tungsten
b) Electrode jelly
c) Silver Graphite
d) Copper Tungsten
View Answer
Explanation: Electrode jelly or paste is used to improve the electrical contact. If the electrodes are intended to be used under the skin of the scalp, needle electrodes are used. They offer the advantage of reducing movement artefacts.
5. Whose electrodes give high skin impedance as compared to ECG?
a) VCG
b) PCG
c) EMG
d) EEG
View Answer
Explanation: EEG electrodes give high skin contact impedance as compared to ECG electrodes. Good electrode impedance should be generally below 5 kilohms. The impedance between a pair of electrodes must also be balanced or the difference between them should be less than 2 kilohms.
6. What are generally designed to have a very high value of input impedance to take care of high electrode impedance?
a) Montages
b) Electrodes
c) Preamplifiers
d) Filters
View Answer
Explanation: 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. EEG preamplifiers are generally designed to have a very high value of input impedance to take care of high electrode impedance.
7. Voltage difference between an active electrode on the scalp with respect to reference electrode at ear lobe or any other part of body is known as ___________ recording.
a) Monopolar
b) Bipolar
c) Unipolar
d) Nonpolar
View Answer
Explanation: 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. This type of recording is called ‘monopolar’ recording.
8. How is bipolar recording done?
a) Omni channel EEG
b) Multi channel EEG
c) Uni Channel EEG
d) Non Channel EEG
View Answer
Explanation: ‘bipolar’ recording is more popular wherein the voltage difference between two scalp electrodes is recorded. Such recordings are done with multi-channel electroencephalographs.
9. EEG signals picked up by surface electrodes are usually small as compared to ECG.
a) True
b) False
View Answer
Explanation: Yes, EEG signals picked up by the surface electrodes are usually small as compared with the ECG signals. They may be several hundred microvolts, but 50 microvolts peak-to-peak is the most typical.
10. A pattern of electrodes on the head and the channels they are connected to are __________
a) Amplifiers
b) Oscilloscope
c) Montage
d) Wires
View Answer
Explanation: A pattern of electrodes on the head and the channels they are connected to is called a montage. Montages are always symmetrical. The reference electrode is generally placed on a nonactive site such as the forehead or earlobe.
11. Where is the reference electrode placed?
a) nasal
b) cervical
c) forehead
d) facial
View Answer
Explanation: A pattern of electrodes on the head and the channels they are connected to is called a montage. Montages are always symmetrical. The reference electrode is generally placed on a nonactive site such as the forehead or earlobe.
12. What is the typical value of the calibration signal?
a) 10 uV/cm
b) 30 uV/cm
c) 50 uV/cm
d) 70 uV/cm
View Answer
Explanation: 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. A typical value of the calibration signal is 50 uV/cm.
13. Preamplifiers used in electroencephalograph have high gain and low noise characteristics.
a) True
b) False
View Answer
Explanation: Yes, 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 minimize stray interference signals from power lines and other electrical equipment.
14. EEG machines have notch filter sharply tuned at _______ Hz as to eliminate mains frequency interference.
a) 10
b) 30
c) 50
d) 70
View Answer
Explanation: EEG machines have a notch filter sharply tuned at 50 Hz so as to eliminate mains frequency interference. 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. 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.
15. What is the typical frequency range of standard EEG machines?
a) 0.025 to 0.05 Hz
b) 0.05 to 0.1 Hz
c) 0.1 to 70 Hz
d) 70 to 140 Hz
View Answer
Explanation: 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.
Sanfoundry Global Education & Learning Series – Biomedical Instrumentation.
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