This set of Clinical Science Multiple Choice Questions & Answers (MCQs) focuses on “Ultrasound”.
1. What property of sound waves acts like the principle of ultrasound?
a) Reflection and Refraction
b) Reflection only
c) Refraction only
d) Propagation
View Answer
Explanation: The ultrasound works on the principle of reflection and refraction. While it is necessary that sound waves need a medium to travel, so we can say propagation is important but it is only because the sound wave gets refracted when the medium changes and are reflected back that the image is formed. Thus, the principle for ultrasound is reflection and refraction.
2. Ultrasound is also useful for __________
i. detecting fault in metal sheets ii. imaging marine depths iii. looking for metals beneath the earth’s surface iv. detecting distances v. detecting earthquakes
a) ii, iii, v
b) i, iv, v
c) i, ii, iv
d) ii, iii
View Answer
Explanation: Ultrasound is used for detecting the fault in metal sheets, imaging marine depths and detecting distances. If the metal sheets have faults like cracks or deformity, the reflected sound waves will not be uniform. SONAR and RADAR are used to detect distances and work on the principle of ultrasound.
3. Which of the following medical imaging modality other than ultrasound does not use any form of radiation?
a) PET Scan
b) SPECT Scan
c) CT Scan
d) MRI
View Answer
Explanation: MRI uses the electromagnetism of the atoms present in the body to get the images while all the other imaging modalities use some sort of radioactivity in order to take the images. Ultrasound relies on the sound waves while MRI relies on the electromagnetic waves. Thus, they are both non radioactive imaging modalities.
4. For which of these areas can the ultrasound be taken for an infant but not for an adult?
a) Cranium
b) Chest
c) Arms
d) Legs
View Answer
Explanation: Bones are natural impedance providers to ultrasound and so if any organ is covered or surrounded by bones, it is not possible or very difficult to take their ultrasound. For an infant, their bones are soft and do not provide so much of a resistance to the passage of the ultrasound waves. Thus, it is possible to take an ultrasound of the brain at an infant stage but not at an adult stage.
5. A piezoelectric crystal is used to produce the ultrasound waves. What kind of ultrasound is produced?
a) Pressure wave ultrasound
b) Electrical wave ultrasound
c) Sound wave ultrasound
d) Simple ultrasound
View Answer
Explanation: A piezoelectric crystal is a special transducer which converts mechanical energy into electrical energy and vice-versa. Thus, when the electrical impulses are given to the transducer, it is converted into mechanical energy. The transducer starts vibrating causing a pressure difference and the ultrasound waves are produced.
6. How is a medium characterized?
a) By its thickness
b) By its acoustic impedance
c) By its water content
d) By its density
View Answer
Explanation: Acoustic impedance is the resistance that a sound wave faces when it propagates from one medium to another in the body. Thickness, density and water content (for a living body) are all factors that are taken into account when measuring the acoustic impedance. Thus the medium is characterized by its acoustic impedance. The impedance offered by the bones is extremely high.
7. The wave velocity of ultrasound in soft tissues is 1540m/s and the impedance offered by it is 1.63 X 106 kg/m2s. What is the density of the soft tissue?
a) 0.1058441 kg/m3
b) 10.58441 kg/m3
c) 1058.441kg/m3
d) 105844.1 kg/m3
View Answer
Explanation: The impedance is given by z = ρc where z = impedance, ρ = density and c = velocity of the ultrasound. Since the wave velocity and the impedance offered are given, ρ = z/c. This results in 1058.441 kg/m3 of density for the soft tissue.
8. Which of the following relations are true?
a) γ increases, penetration of sound increases, resolution decreases
b) γ increases, penetration of sound decreases, resolution decreases
c) γ increases, penetration of sound decreases, resolution increases
d) γ decreases, penetration of sound increases, resolution increases
View Answer
Explanation: When the frequency (γ) of the sound waves increases, it gains more energy to overcome the impedance barrier and so is able to penetrate deeper. However, the penetration may not be uniform in all places and reflection may be uneven thus it affects the resolution of the image.
9. When an abdominal ultrasound is done, why is it advised to have a full bladder?
a) To have a good acoustic window
b) To increase the water content
c) To lower impedance
d) To allow for better propagation of waves
View Answer
Explanation: Acoustic window is a small opening through which the sound waves can pass and can help image the structures beyond. When the bladder is full, it is properly stretched and the folds of the bladder do not provide any impedance. The water helps in the better propagation of the sound and visualization of the structures beyond the bladder.
10. What does the red dot on the probe help within the produced image?
a) To check if the correct probe was used
b) To check the probe orientation
c) To check the depth of the probe that was used
d) To check the plane of the image.
View Answer
Explanation: When the probe is being used, it can move in various ways but the image being formed is a horizontal image. Thus, the red dot at the head of the probe appears to the left of the image and helps in working out the orientation of the organ or the foetus.
Sanfoundry Global Education & Learning Series – Clinical Science.
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