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Semester 3 Advanced Ultrasound Physics > Harmonics and Contrast Agents > Flashcards

Harmonics and Contrast Agents Flashcards

Week 4

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1
Q

What is fundamental frequency?

A

frequency created by the transducer.

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2
Q

What is harmonic frequency?

A

2x’s the fundamental frequency.

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3
Q

How does harmonic frequency happen?

A

during nonlinear behavior

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4
Q

What is fundamental imaging?

A

created by processing reflections that have the same frequency as transmitted sound.

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5
Q

What are harmonic images?

A

Images created by processing reflections the are twice the fundamental frequency.

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6
Q

What are 2 forms of harmonics?

A
  1. Tissue harmonics
  2. contrast harmonics
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7
Q

Why is harmonic imaging helpful?

A

helps improve poor quality images, because harmonic frequency waves undergo less distortion.

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8
Q

What does linear behavior mean?

A

proportional, linear systems respond in an even manner.

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9
Q

What does nonlinear behavior mean?

A

Irregular, behaves unevenly.

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10
Q

When are harmonics frequency created?

A

During transmission

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11
Q

What is tissue harmonics?

A

The minuscule amount of energy is converted from fundamental frequency to harmonic frequency.

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12
Q

Fundamental imaging will have what?

A

Lower quality imaging and have more noise.

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13
Q

What is the significance of the gradual development of a harmonic signal?

A

The minuscule amount of energy that converts from fundamental frequency to harmonic frequency.

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14
Q

Tissue harmonics do not exist where?

A

Superficial depths.

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15
Q

What are some advantages of tissue harmonics?

A
  1. improve signal to noise ratio
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16
Q

Weak beams do not create what?

A

Tissue harmonics

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17
Q

True of False, Harmonic strength weakens as it propagates deeper in the body?

A

True

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18
Q

Where is the beam strongest?

A

At the focus, along the beams main axis.

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19
Q

True or false, Harmonics are present as they leave the transducer?

A

False

20
Q

Narrow bandwidth creates degraded what?

A

Spatial resolution

21
Q

What is pulse inversion harmonic technique?

A

2 beams at 180 degrees out of phase completely deconstruct, leaving harmonic signal that the original resonant frequencies create.

22
Q

What is a disadvantage of pulse inversion harmonics?

A

frame rate is halved.

23
Q

What is power modulation?

A

Where during reception, the reflections from the first pulse is doubled then subtracted from the weaker second wave, completely canceling each other out.

24
Q

What are some advantages of power modulation?

A

1.less distortion
2. better spatial resolution

25
Q

Why is it so significant that only strong sound beams create harmonic signals?

A

creates less distortion and less noise.

26
Q

contrast agents are also known as what?

A

microbubbles

27
Q

Contrast agents meet what 5 requirements?

A
  1. safe
  2. metabolically inert
  3. long lasting
  4. strong reflector of ultrasound
  5. small enough to pass through capillaries
28
Q

When is contrast harmonics created?

A

during reflection

29
Q
A
30
Q

What is resonance?

A

the contraction and expansion of microbubbles

31
Q

Saline bubble study is used to evaluate what?

A

The right side of the heart.

32
Q

Contrast agents or micro bubbles are used to evaluate what?

A

the left side of the heart.

33
Q

What is the goal of using contrast agents?

A

to create a reflection that helps to delineate the left ventricle wall from blood.

34
Q

True or false, micro bubbles act in a nonlinear manner when struck by sound?

A

True

35
Q

True or false, the impedance of the contrast agent is the same as the impedance of soft tissue?

A

False, it is different.

36
Q

What expands the bubble in a contrast agent?

A

Peak rarefactions expand the bubble.

37
Q

True or False, grating lobes are capable of producing harmonic signals?

A

False

38
Q

The purpose of power modulation harmonic imaging is to…..?

A

Double and then subtract from the second reflection to remove the fundamental frequency.

39
Q

Within the first 2cm of tissue harmonics does not exist.

A

False

40
Q

What is the name of the image that processes reflections at the same frequency as the transmitted (or resonant) frequency?

A

Fundamental image

41
Q

True or False, tissue harmonics are created during harmonics?

A

True

42
Q

Agitated saline bubble contrast agents are used for:

A

Right side evaluation for shunts.

43
Q

The meaning of resonance with microbubbles contrast agents:

A

When exposed to beams of adequate strength contrast harmonics are created because of nonlinear changes in bubble size.

44
Q

The amount of contrast harmonics produced may be estimated by a number called?

A

Mechanical index

45
Q

The strength of a tissue harmonic wave grows as the transmitted sound travels deeper into the tissue?

A

True

Semester 3 Advanced Ultrasound Physics (6 decks)

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