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Ultrasound Physics > Ch. 8, 9, & 10 > Flashcards

Ch. 8, 9, & 10 Flashcards

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1
Q

T/F

The acoustic impedence of the matching layer is approximately the same as the acoustic impedance.

A

False. The impedance of the matching layer is greater than the impedance of the skin

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2
Q

T/F

Imaging transducers are usually of high rather than low bandwidth.

A

True

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3
Q

T/F

A very high Q factor transducer is used more often in diagnostic imaging transducers than a low Q factor.

A

False.

Imaging transducers are low q

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4
Q

T/F

A pulse with a long pulse duration is likely to have a narrow bandwidth

A

True. Longer events tend to have a narrow bandwidth. Shorter have a wider bandwidth

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5
Q

T/F

The damping material in a transducer increases the sensitivity

A

False

Damping reduces sensitivity

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6
Q

T/F

The damping material in transducer increases the pulse length

A

False

Shortens pulse length

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7
Q

T/F

The damping material in a transducer decreases pulse duration

A

True

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8
Q

T/F

The damping material in a transducer improves the system’s lateral resolution.

A

False

Damping does not affect lateral resolution

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9
Q

T/F

The damping material in a transducer improves the system’s longitudinal resolution

A

True

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10
Q

T/F

The damping material in a transducer decreases bandwidth

A

False

Damping increases bandwidth

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11
Q

T/F

The damping material in a transducer decreases the quality factor

A

True

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12
Q

T/F

If the frequency of the electrical excitation voltage of a pulsed wave transducer is 6MHz, then the operating frequency of the transducer is 6 MHz.

A

False.

Pulse wave transducers, the frequency of sound Is not determine by electrical signal

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13
Q

T/F

If the pulse repetition frequency of a transducer is increased, then the frequency of sound produced by the transducer remains the same

A

True

Frequency and PRF are not related

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14
Q

T/F

The diameter of the active element of a transducer helps deter the frequency of a sound that the transducer creates.

A

False

Diameter of the active element does not determine the frequency of sound created by transducer

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15
Q

T/F

If the frequency of the electrical excitation voltage of a continuous wave transducer is 6MHz, then the operating frequency of the transducer is 6MHz.

A

True

Frequency of voltage and frequency are identical with continuous ave transducers

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16
Q

T/F

Two piezoelectric crystals are made from the same material the thicker the crystal will make a pulsed transducer with a higher frequency.

A

False

Thicker active elements create sound with lower frequency not higher

17
Q

T/F

Two piezoelectric crystals are made from the same material. The thicker will make a continuous wave transducer with a lower frequency.

A

False

With continuous wave transducer, active element thickness does not determine the sound beam’s frequency.

18
Q

T/F

The normal propagation speed in piezoelectric material is about 3 to 5 times greater than that in soft tissue.

A

True

Sound travels faster in PZT than soft tissue

19
Q

The impedance of a transducer active element is 1,900,000 Rayls, and the impedance of the skin is 1,400,000 Rayls. What is an acceptable impedance for the matching layer?

1,200,000
1,400,000
1,726,000
1,950,000

A

1,726,000

The impedance of the matching layer is btw that of the active element and the skin

20
Q

What crystals will produce sound with the lowest frequency?

A

Thick and with a low speed

21
Q

Which type of transducer has a greater Q factor: therapeutic or imaging?

A

Therapeutic have a higher Q factor than imaging transducers

22
Q

Which type of transducer has a greater bandwidth: continuous wave or imaging?

A

Imaging

23
Q

Which type of transducer has more backing material: therapeutic or imaging?

A

Imaging

24
Q

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

A

Improve image quality

25
Q

A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8MHz. What is the bandwidth?

A

8-6= 6MHz

26
Q

A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8MHz. What is the main frequency?

A

Main frequency is 5 MHz

27
Q

A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8MHz. What is the Q factor?

A

.8

5MHz/6MHz

Unitless value less than 1. Bandwidth has no units.

28
Q

What is the ability to accurately distinguish two structures lying close together called?

A

Resolution

29
Q

The ability to distinguish two structures lying close together front to back or parallel to the sound beam is called

A

Longitudinal, axial, range, radial, depth resolution

30
Q

Axial resolution and lateral resolution are measured with units of ___.

A

Distance such as mm

31
Q

When the number of cycles in a pulse increases while the frequency remains the same, the numerical value of the range resolution ___.

Increases
Decreases
Same

A

Increases

With more cycles, the longer the pulse so the numerical value of range resolution increases

32
Q

When the number of cycles in a pulse increases (more ringing) while the frequency remains the same, the image quality

Improves
Degrades
Remains the same

A

Degrades

33
Q

____ frequency transducers have the best range resolution.

A

High

34
Q

4 synonyms for axial range resolution

A 
Longitudinal 
Axial 
Range
Radial
Depth
35
Q

Synonyms for lateral resolution

A

Lateral
Angular
Transverse
Azimuthal

36
Q

The length of a pulse is 8 mm. What is the minimum stance btw two reflectors, positioned one in front of the other, that still produces two echoes on our image?

A

4 mm

-this value is 1/2 the pulse length

Ultrasound Physics (6 decks)

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