Chapter 17 Flashcards

Harmonics and Contrast Agents

1
Q

____ ____ is the creation of an image from sound reflections at twice the frequency of the transmitted sound.

A

Harmonic imaging

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2
Q

____ ____ is the transmitted frequency.

A

Fundamental frequency

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3
Q

____ ____ is twice the transmitted frequency.

A

Harmonic frequency

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4
Q

What type of behavior means proportional or symmetrical - systems respond in an even manner.

A

Linear behavior

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5
Q

What type of behavior means irregular or disproportionate - systems respond in an uneven manner

A

Non-linear behavior

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6
Q

Harmonic frequency sound waves arise from ____ behavior.

A

Non-linear

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7
Q

Harmonic imaging can produce a more accurate image because harmonic frequency waves undergo less ____ than fundamental sound waves.

A

Distortion

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8
Q

As a sound wave travels in the body, a small amount of energy is converted from the ____ frequency to the ____ frequency.

A

Fundamental; Harmonic

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9
Q

Tissue harmonics to be created during ____.

A

Transmission

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10
Q

A sound wave is a series of ____ and ____.

A

Compressions and rarefactions

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11
Q

Sound travels faster through ____ and slower through ____.

A

Compressions; Rarefactions

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12
Q

During ____ ____, (no harmonics) significant amounts of artifact arise within the first few centimeters of tissue

A

Fundamental imaging

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13
Q

During ____ ____ imaging NO harmonic signals are generated at extremely superficial depths.

A

Tissue harmonic

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14
Q

As sound travels ____ in tissue, the strength of the harmonic wave becomes larger.

A

Deeper

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15
Q

____ sound beams do not create tissue harmonic.

A

Weak

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16
Q

____ strength sound beams create a tiny amount of tissue harmonics.

A

Intermediate

17
Q

____ sound beams create significant tissue harmonics.

18
Q

Side lobes and grating lobes are usually ____ so little or no harmonics are created in them.

19
Q

____ ____ ____ use the distortion free harmonic reflections, while eliminating the distorted fundamental reflections.

A

Pulse inversion harmonics

20
Q

Pulse inversion Harmonics is a more successful method of separating ____ and ____ frequencies.

A

Fundamental and harmonic

21
Q

How does pulse inversion harmonics work?

A

Two pulses are transmitted down a scan line

  • 1st pulse is a typical pulse
  • 2nd pulse is an inverted copy (it’s opposite)

Where a compression occurs in the 1st pulse, a rarefaction occurs in the 2nd

Upon arriving back to the receiver, these pulses are combined.

22
Q

____ ____ (microbubbles) are gas bubbles encased in a shell that are injected into the circulation (I.V. typically) or swallowed.

A

Contrast agents

23
Q

Contrast agents must meet five requirements:

A
  1. Safe
  2. Metabolically inert –it won’t change in a biological system
  3. Long lasting
  4. Strong reflector of ultrasound
  5. Small enough to pass through capillaries
24
Q

Constrast harmonics are created during ____.

A

Reflection

25
This expanding and shrinking when a microbubble is in a sound beam is called ____.
Resonance
26
What is the most important formation of contrast harmonics?
Rarefaction
27
When a microbubble is exposed to the high pressure component of a sound wave, the microbubble ____.
Shrinks
28
When a microbubble is exposed to the low pressure component of a sound wave, the microbubble ____.
Expands
29
____ ____ is a number that estimates the amount of contrast harmonics produced.
Mechanical index (MI)
30
The mechanical index increases with:
1. Lower frequency sound 2. Stronger sound waves
31
Microbubbles the size of red blood cells just so happen to resonate in the ____MHz – ____MHz range
2 MHz – 4 MHz
32
Two characteristics of contrast agents that are important are the ____ ____ and the ____.
Outer shell; Gas
33
The shell needs to be ____ so the microbubbles can change shape.
Flexible
34
The gas needs to be made of ____ molecules so that it remains trapped within the bubble, no leaking out!
Large
35