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50 Cards in this Set
- Front
- Back
The creation of an image from sound reflections at twice the frequency of the transmitted sound is called what?
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Harmonics
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The frequency of sound created by the transducer and transmitted into the body is called what?
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Fundamental Frequency
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Twice the fundamental frequency is called what?
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Harmonic Frequency
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The image created by processing reflections that have the same frequency as the transmitted sound is called what?
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Fundamental Image
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The image created by processing reflections that are twice the fundamental frequency is called what?
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Harmonic Image
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Harmonic frequency sound arises from what type of behavior?
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Non-Linear Behavior
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Behavior which is proportional or symmetrical, responding in an even manner, is called what?
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Linear Behavior
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Behavior which is disproportionate or irregular, responding in an uneven or asymmetrical manner, is called what?
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Non-Linear Behavior
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Microbubbles that are ingested or injected and have a different acoustic fingerprint than blood or tissue creating strong reflections, are called what?
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Contrast Agents
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The following are five requirements for what?
- safe - metabolically inert - long lasting - strong reflector of ultrasound - small enough to pass through capillaries |
Contrast Agents
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Strong signals, such as those generated by contrast agents, generate significant ___
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Harmonics
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The creation of ___ results from the ___ behavior of microbubbles when sound strikes them
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Contrast Harmonics
Non-Linear |
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A sound wave is an oscillation of ___
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Pressure (mmHg)
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Describe why microbubbles demonstrate non-linear behavior when struck by suond waves of adequate strength?
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Microbubbles grow and shrink in size - uneven changes
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When exposed to the high pressure component of a sound wave, a microbubble will ___
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Shrink
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When exposed to the low pressure component of a sound wave, a microbubble will ___
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Grow
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As microbubbles grow and shrink, a small amount of energy is transferred from the fundamental frequency to the ___
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Harmonic Frequency
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The amount of contrast harmonics produced is estimated by a number called the ___
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Mechanical Index
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What kind of number is indicated by:
- weaker sound waves (less pressure) - higher frequency |
Lower Mechanical Index
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What kind of number is indicated by:
- stronger sound waves (more pressure) - lower frequency |
Higher Mechanical Index
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Why are microbubbles strong scatterers of sound waves?
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They vibrate from sound in the 2-4 MHz range, causing even greater resonance
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Is there a direct (linear) relationship between mechanical index and harmonic creation?
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No
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What kind of harmonics does a low mechanical index number create?
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Low MI (< 0.1) = No Harmonics (just backscatter)
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What kind of harmonics does an intermediate mechanical index number create?
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Intermediate MI (0.1 - 1.0) = Moderate Harmonics
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What kind of harmonics does a high mechanical index number create?
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High MI (> 1.0) = Significant Harmonics
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What kind of mechanical index number do the following factors describe:
- no harmonics - backscatter - linear behavior - higher frequency sound - low beam strength |
Low Mechanical Index (< 0.1)
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What kind of mechanical index number do the following factors describe:
- strong harmonics - resonance - non-linear behavior - lower frequency sound - higher beam strength |
Intermediate Mechanical Index (0.1 - 1.0)
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What kind of mechanical index number do the following factors describe:
- strongest harmonics - bubble disruption - extreme non-linear behavior - lowest frequency sound - highest beam strength |
Highest Mechanical Index (> 1.0)
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What are two important characteristics of contrast agents?
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1. The nature of the outer shell
2. The gas that fills it |
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What determines the contrast agent's stability and longevity in the circulatory system?
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The relationship between the outershell and the internally trapped gas
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What happens to gas bubbles without outer shells (such as found in agitated saline)?
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They shrink and quickly dissipate
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What happens to gass bubbles with rigid outer shells?
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Rigid outer shells tend to fracture causing bubble disruption
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When are contrast harmonics created?
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During Reflection
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What kind of behavior creates contrast harmonics?
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Non-Linear Behavior
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Contrast harmonics are determined by the ___ and ___ of the contrast agent
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Shell & Gas
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As a sound wave travels through the body, a miniscule amount of energy is converted from the fundamental frequency to the harmonic frequency. This is called what?
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Tissue Harmonics
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What is a series of compressions and rarefactions called?
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Sound Wave
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Sound travels at slightly uneven speeds through soft tissue - ___ through compressions and ___ through rarefactions. This is ___ behavior.
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Faster
Slower Non-Linear |
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Does the strength of the harmonic wave grow or shrink as sound travels in tissue?
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Grows
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Why do tissue harmonic signals remain distortion free through superficial depths?
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Fundamental frequencies are distorted by superficial layers, but harmonics develop deeper in tissue (avoiding the distortion causing superficial layers)
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What behavior describes the relationship between sound beam strength and harmonic creation?
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Non-Linear
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Weak sound beams create how much harmonics:
A. None B. Small Amount C. Significant Amount |
A
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Intermediate sound beams create how much harmonics:
A. None B. Small Amount C. Significant Amount |
B
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Strong sound beams create how much harmonics:
A. None B. Small Amount C. Significant Amount |
C
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Sound beams that are ___ likely to create artifacts are ___ likely to create harmonics
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Least
Most |
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Are harmonics created by grating/side lobes?
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No, because they are too weak
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Which are stronger: contrast harmonics or tissue harmonics?
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Contrast Harmonics
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In contrast harmonics, what action creates the strongest harmonic signals?
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Bubble Disruption
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These factors describe what type of harmonics:
- created during transmission - occurs as sound propagates - results from non-linear behavior of transmitted sound beam - weaker harmonic signal |
Tissue Harmonics
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These factors describe what type of harmonics:
- created during reflection - occurs when MI > 0.1 - results from non-linear behavior of microbubbles - stronger harmonic signal |
Contrast Harmonics
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