Multiple choice questions and answers

Chapter 15 Multiple choice questions and answers

MULTIPLE CHOICE QUESTIONS

Select all the correct answers in the following

The Ultrasound Beam

1. An ultrasound beam passing through the body

a is attenuated

b produces heating of tissues

c can be reflected

d produces ionization

2. Ultrasonic pulses

a are poorly transmitted by liquids

b are poorly transmitted by air gaps

c are partially reflected at interfaces between two liquid media

d are partially transmitted at interfaces between two solid media

3. The Fraunhofer zone is the

4. Which of the following statements are true concerning the nature of diagnostic ultrasound in liver?

a The wave speed and frequency are constant regardless of the wavelength

b The wave speed is constant regardless of the wavelength

c Wave speed increases with the increasing frequency

d None of the above

5. Which of the following characteristics of diagnostic ultrasound applies also to X-radiation?

a It is a wave phenomenon

b Its wave speed and frequency are inversely proportional

c Matter must be present for transmission

d Molecular compression and rarefaction occur

6. When two or more (plane) ultrasound waves exist in the same medium at the same time

a they will interfere constructively if traveling with the same direction and phase

b standing waves will be produced if they are traveling with the same direction and phase

c standing waves will be produced if they are traveling in the same direction but out of phase

d None of the above

7. Specific acoustic impedance as applied to diagnostic ultrasound increases with increasing

8. When the diagnostic ultrasound beam is incident on the surface separating different tissues

a none of the beam will be transmitted

b none of the beam will be reflected

c reflection can occur when the beam is at right angles to the interface

d when incident at greater than the critical angle, there will be total transmission

9. When an acoustic wave is transmitted through soft tissue

a there will be no reduction in intensity

b attenuation will occur

c energy will be transmitted by way of ionization and excitation

d energy will be transmitted by way of Compton scattering

11. When a transmitted ultrasound beam changes direction across an interface, this is called

12. Ultrasound and X-rays differ in which of the following ways?

a One is transverse, the other longitudinal

b One requires matter, the other does not

c One has constant wave speed, the other variable wave speed (in soft tissue)

d All of the above

13. Diagnostic ultrasound intensity is often measured in

14. Intensity is equal to

c amplitude/distance

d frequency/wavelength

15. Diagnostic ultrasound intensity

a increases with increasing frequency

b is a measure of particle displacement in the conduction medium

c is measured in mW/cm²

d is the same as ultrasound power

16. As ultrasound is transmitted through tissue, its intensity decreases because of

17. Acoustic reflectivity

a is determined by acoustic impedance at an interface

b equals 100 if Z₁ = Z₂

c is higher for an air–soft-tissue interface than a bone–soft-tissue interface

d increases with increasing frequency

18. An ultrasound wave may be described as

a a longitudinal pressure wave

b a transverse wave

c being formed by particle oscillations

d changes in electrical properties of tissues

19. Ultrasound used for diagnosis

a has a frequency in the region 2 to 10 kHz

b has a velocity in air of 1500 ms⁻¹

c will not travel through a vacuum

d is produced and detected by a transducer

20. Ultrasound has the following properties. It

a can be deflected by a magnetic field

b is attenuated in tissue

c has a sinusoidal wave form

d can travel through water

21. An ultrasound beam is attenuated

a by reflection at a tissue interface

b and causes ionization of atoms

c by scattering

d by absorption in tissues

22. Greater than 50% energy reflection will take place at a

a soft-tissue–bone interface

b water–soft-tissue interface

c soft-tissue–gas interface

d muscle–fat interface

23. The magnitude of the reflected signal

a decreases as the angle of incidence approaches 90 degrees

b depends on the change of acoustic impedance at an interface

c is independent of the acoustic impedance

d depends on the frequency of the beam

24. Interference phenomena

a may occur when two waves interact

b are more common with continuous wave ultrasound

c always produce a wave form of reduced amplitude

d may be of value to ultrasound

25. Acoustic impedance depends on

a the intensity of the ultrasound beam

b the elasticity of the tissue

c tissue density

d tissue temperature

26. In which of the following materials is the speed of ultrasound greatest?

27. What is the wavelength of a 5 MHz ultrasound pulse in soft tissue?

28. As frequency increases

a wavelength increases

b imaging depth decreases

c propagation speed decreases

29. The frequency of a sound wave is determined by

a the media through which it travels

b its propagation

30. As frequency increases, the attenuation coefficient

c stays the same

d attenuation coefficient not affected by frequency

31. Which of the following sound frequencies would include diagnostic ultrasound?

32. Velocity of ultrasound

a depends on the transmitted frequency

b varies for different materials

c is temperature dependent

d is equal for muscle and bone

33. The velocity of an ultrasound beam may be determined by measuring the

a time taken for a pulse to be returned through a Perspex block of a known thickness

b time taken for a pulse to be returned through a known depth of water

c reflection of the beam by a wire mesh placed in water

d distance between peaks of the wave form

34. The propagation speed of sound through soft tissue is

d 1230 cms⁻¹

35. Given the various physical characteristics of ultrasound, then it is true that

a its speed is the same in all materials

b its speed does not depend on its frequency

c its speed depends on the density of the supporting medium

d its speed increases with frequency

36. Lateral resolution can be improved by

37. Axial resolution can be improved by

d increasing operating frequency

38. The resolution of an ultrasound beam may be determined by

a imaging a series of wires at varying depth from the transducer face

b imaging a series of wires all the same depth from the transducer face

c compound scanning around a Perspex block containing a single central wire

d linear scanning of a single wire in awater bath

40. The axial resolution of a transducer is primarily determined by

a spatial pulse length

b the transducer diameter

c the acoustic impedance of tissue

41. The lateral resolution of a transducer is primarily determined by

a spatial pulse length

b the beam width

c the acoustic impedance of tissue

d applied voltage

The Transducer

1. The fundamental operating principle of medical ultrasound transducers is

a Snell’s law

b ALARA principle

c piezoelectric effect

d impedance effect

2. Which one of the following quantities varies the most with distance from the transducer face?

a Axial resolution

b Lateral resolution

3. What determines the transducer frequency selection for diagnostic ultrasound?

a Intensity and resolution

b Intensity and propagation speed

c Scattering and impedance

d Resolution and penetration

4. Which of the following improves sound transmission from the transducer element into the tissue?

a Matching layer

b Doppler effect

c Damping material

d Coupling medium

5. The active elements of the diagnostic ultrasound transducer

a may be crystalline material

b operate on the basis of the photoelectric effect

c convert electrical energy into mechanical energy

d convert mechanical energy into electrical energy

6. The principle on which the ultrasound transducer operates is the

a photoelectric effect

b crystalline effect

c piezoelectric effect

d transducer effect

7. A piezoelectric crystal may be made of

b calcium tungstate

d lithium fluoride

Tags: Ultrasound Physics and Technology How, Why and When

Mar 10, 2016 | Posted by admin in ULTRASONOGRAPHY | Comments Off

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