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Ultrasound Physics > Chapter 6-9 quiz > Flashcards

Chapter 6-9 quiz Flashcards

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1
Q

What is the region from the transducer to the smallest cross-sectional area of a sound beam called?

A

Near zone

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2
Q

The area that starts at the beam’s smallest diameter and extends deeper is:

A

The Fraunhofer zone

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3
Q

What is the point or location where a beam reaches it smallest dimension?

A

Focus

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4
Q

All of the following are true of the focus except:

A

It is at the start of the fresnel zone

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5
Q

Two ultrasound systems are identical except for the PRP of the emitted pulse. Which system will have the deeper focus?

A

Their foci will be at the same depth

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6
Q

For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?

A

Small diameter, low frequency

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7
Q

For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the deepest focus?

A

Large diameter, high frequency

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8
Q

As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in a minimum beam divergence deep in the far zone?

A

High frequency, large diameter

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9
Q

As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in the greatest beam divergence deep in the far zone?

A

Low frequency, small diameter

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10
Q

All of the following terms describes the shape of a sound wave created by a tiny fragment of PZT except:

A

Hourglass shape

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11
Q

Huygens’ principle is based on ____

A

Interference

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12
Q

Which of the following explains the difference in sound beam shape created by a disc-shaped crystal from that of a small chip of PZT?

A

Huygen’s principle

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13
Q

Two ultrasound systems are identical except for the diameter of the transducer’s piezoelectric crystal. Which system has the deepest focus?

A

The one with the larger diameter crystal

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14
Q

In which region of a sound beam is focusing most effective?

A

The end of the near zone

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15
Q

The focus of an ultrasound beam is the location where the _______.

A

Optimum transverse resolution is

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16
Q

T or F? In comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone.

A

True

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17
Q

In an imaging transducer, what is the purpose of attaching the backing material to the PZT?

A

Improve image quality

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18
Q

Which component of an ultrasound system is made of lead zirconate titanate?

A

Transducer’s active element

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19
Q

T or F. The purpose of the backing material of an ultrasound transducer is to shorten the pulses, thereby creating images with better image quality.

A

True

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20
Q

Which component of an ultrasound transducer is made from a slab of epoxy embedded with tungsten?

A

The damping material

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21
Q

How thick is the active element of a 3MHz pulsed wave transducer?

A

Half the wavelength of the sound wave in the PZT

22
Q

The PZT crystal of a transducer typically has a impedance higher that the impedance of the skin?

A

True

23
Q

Which of the following lists orders the impedance from highest to lowest?

A

PZT, matching layer, gel, and skin

24
Q

What is the thickness of the matching layer of a 2 MHz pulsed wave transducer?

A

One-quarter the wavelength of sound in matching layer

25
Q

T or F. The matching layer decreases the Q factor.

A

True

26
Q

What is a decibel?

A

A relationship between two numbers

27
Q

What is the decibel notation for an acoustic signal that is attenuated?

A

Negative

28
Q

The power in a wave is increased to ten times its original value. How many decibels describe this change?

A

10

29
Q

The intensity of an ultrasound wave is changed by -6dB. This means that the current intensity is _____ as much as its original level.

A

One-fourth

30
Q

The scale associated with the decibel notation is ____

A

Logarithmic

31
Q

What does a 3 dB change is a value intensity mean?

A

The value has doubled

32
Q

As sound propagates through a medium the total power in the wave decreases. What is the entire process called?

A

Attenuation

33
Q

Which of the following is not one of the physical processes that contribute to attenuation of ultrasound waves passing through soft tissue?

A

Focusing

34
Q

What is the dispersion of a sound wave uniformly in many different after striking a very small particle?

A

Rayleigh scattering

35
Q

Which of the following is considered a Rayleigh scatter?

A

Blood

36
Q

Which of the following is true to diffuse reflection?

A

Sound reflects in many directions

37
Q

What is the amount of attenuation per centimeter that a sound wave undergoes called?

A

Attenuation coefficient

38
Q

A sound beam travels 9 cm in soft tissue. The attenuation coefficient is 3 dB/cm. What is the total attenuation that the sound beam experienced?

A

27 dB

39
Q

An 8 MHz beam travels in soft tissue through a path length of 5 cm. What is the value of the attenuation?

A

20 dB

40
Q

Which of the following describes an angle with a measure of 45 degrees?

A

Acute

41
Q

Which of the following best describes an angle with a measure of 123?

A

Obtuse

42
Q

Which term does not belong in the group below?

A

Oblique

43
Q

Which term has a meaning other than normal incidence?

A

Oblique incidence

44
Q

A sound beam with an intensity of 45 w/cm squared strikes a boundary and 70% of the wave’s intensity is reflected. How much is transmitted?

A

30%

45
Q

What event does snell’s law govern?

A

Refraction

46
Q

Which of the following best describes the process described by snell’s law?

A

Transmission with oblique incidence

47
Q

The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to PRP?

A

It is doubled

48
Q

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time?

A

130 us

49
Q

A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 us. What is the total distance that the pulse traveled?

A

4 cm

50
Q

The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm What happens to PRF?

A

It is halved

Ultrasound Physics (30 decks)

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