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Ultrasound Physics > Chapter 9 > Flashcards

Chapter 9 Flashcards

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1
Q 
What is the best estimate of the diameter of width of the sound beam as it exits the transducer?
6 mm
9 mm
12 mm
8 mm
A

12 mm

At its beginning, the sound beam diameter its the same as the diameter of the active element

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2
Q

What is the diameter of the sound beam at a depth of 8 cm?

A

6 mm

At the end of the end of the near zone (8 cm), the beam diameter is one half the transducer diameter.

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3
Q

What is the diameter of the sound beam at a depth of 16 cm?

A

12 mm

At a depth equal to 2 near zone lengths, the beam diameter is the same as the diameter of the active element

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4
Q

At what depth is the focus?

A

8 cm

The focal depth is the same as the length of the near zone

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5
Q

What depth marks the beginning of the focal zone?

A

6 cm
The foal zone is the region around the focus. In this example, the focal zone begins at a depth 2 cm shallower that the focus.

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6
Q

What depth marks the end of the focal zone?

A

8 mm
The focal zone is the region around the focus. In this example, the focal zone ends at a depth 2 cm deeper than the focus.

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7
Q

At which of the following depths is the beam narrowing?

A

6 cm

The beam narrows within the near zone.

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8
Q 
At which of the following depths is the depth widening?
2 cm
6cm
8cm
9.375
A

9.375

The beam only widens or diverges in the far zone. The only depth within the far zone is 9.375

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9
Q 
At which of the following depths is the beam most likely to have the same diameter as it has at a depth of 11 cm?
1 cm 
3cm
5cm
8 cm
A

5 cm
Think of the beam as being symmetrical around the focus. Thus, the beam diameter will be similar when it is 3 cm shallower and 3 cm deeper than the focus

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10
Q

Which of the following terms does not belong?

A

End of the Fraunhofer zone

The end of the Fraunhofer zone is the very end of the sound beam

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11
Q

A pair of 6 MHz probes are identical except for the active element diameter. The active element diameters are 6 mm and 10 mm, respectively. The sound beam of which probe will have a shallower focus?

A

The probe with a 6 mm active element has a shallower focus. Smaller diameter crystals produce beams with shallower foci.

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12
Q

A air of 9 mm diameter probes are identical except for frequency, which is 3 MHz and 6 MHz, respectively. Which beam will have a shallower focus?

A

The 3 MHz beam has a shallower focus. Focal depth increases with increasing frequency. The beam created by the 6 MHz probe has a deeper focus.

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13
Q 
Which of the following probes creates a beam with the deepest focus?
4mm diameter, 4 MHz
6mm diameter, 8MHz
6mm diameter, 2 MHz
5mm diameter, 8 MHz
A

6mm diameter, 8 MHz

Longer focal lengths are associated with large diameter, high frequency probes.

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14
Q 
Which of the following probes creates a beam with the shallowest focus?
4mm diameter, 4 MHz
6mm diameter, 8MHz
4mm diameter, 2 MHz
5mm diameter, 8 MHz
A

4mm diameter, 2 MHz

Shorter focal lengths are associated with small diameter, low frequency probes.

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15
Q

Which of the following probes creates a beam with the shallowest focus?

A

Small diameter, low frequency

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16
Q

Active element diameter and near zone length are ___________ related.

A

Directly

17
Q

Transducer frequency and near zone length are _________ related

A

Directly

18
Q

Wavelength and near zone are ________ related.

A

Inversely

19
Q

A pair of 6 MHz probes are identical except for the active element diameters, which are 6 mm and 10 mm, respectively. Which beam will be more compact in the far field?

A

The probe with 10 mm active element has a less divergent beam. Larger diameter crystals product beams that diverge less in the far field.

20
Q

A pair of 9 mm diameter probes are identical except for frequencies, which are 3 MHz and 6 MHz. Which sound beam will spread out more in the far field?

A

The 3 MHz beam

21
Q 
Which of the following probes creates a beam with the least divergence?
4 mm diameter, 4 MHz
6 mm diameter, 8 MHz
6 mm diameter, 2 MHz
5 mm diameter, 8 MHz
A

6 mm diameter, 8 MHz

Divergence is minimalized with large diameter, high frequency probes.

22
Q

Which of the following probes creates a beam with the least divergence?

A

Small diameter, low frequency

23
Q

Transducer frequency and beam divergence are __________ related.

A

Inversely

24
Q

Active element diameter and beam divergence are __________ related.

A

Inversely

25
Q

The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the near zone length?

A

Increases

26
Q

The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the far zone?

A

Decreases

27
Q

The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the wavelength?

A

No change

28
Q

The frequency of a transducer does not change. If the diameter of the new piezoelectric crystal increases, what happens to the beam diameter in the near zone?

A

Increases

29
Q

At what location is the beam diameter three times greater than the transducer diameter?

A

At the depth equal to four focal lengths

30
Q

What is the shape of a sound beam created by a tiny piece of PZT?

A

V shape

31
Q

Which of the following explains why a sound beam created by a disc-shaped crystal is hourglass shaped?

A

Huygens’ principle

32
Q 
Which of the following locations is the deepest?
End of the fresnel zone
End of the focal zone
End of the fraunhofer zone
End of the near zone
A

End of the Fraunhofer zone

33
Q 
Which of the following locations is the most shallow?
Beginning of the far zone
Beginning of the focal zone
Focal depth
Beginning of the Fraunholder zone
A

Beginning of the focal zone

Ultrasound Physics (30 decks)

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