Ultrasound Physics - 17\harmonics & Contrast Agents

Front 1

The creation of an image from sound reflections at twice the frequency of the transmitted sound is called what?

Back 1

Harmonics

Front 2

The frequency of sound created by the transducer and transmitted into the body is called what?

Back 2

Fundamental Frequency

Front 3

Twice the fundamental frequency is called what?

Back 3

Harmonic Frequency

Front 4

The image created by processing reflections that have the same frequency as the transmitted sound is called what?

Back 4

Fundamental Image

Front 5

The image created by processing reflections that are twice the fundamental frequency is called what?

Back 5

Harmonic Image

Front 6

Harmonic frequency sound arises from what type of behavior?

Back 6

Non-Linear Behavior

Front 7

Behavior which is proportional or symmetrical, responding in an even manner, is called what?

Back 7

Linear Behavior

Front 8

Behavior which is disproportionate or irregular, responding in an uneven or asymmetrical manner, is called what?

Back 8

Non-Linear Behavior

Front 9

Microbubbles that are ingested or injected and have a different acoustic fingerprint than blood or tissue creating strong reflections, are called what?

Back 9

Contrast Agents

Front 10

The following are five requirements for what?
- safe
- metabolically inert
- long lasting
- strong reflector of ultrasound
- small enough to pass through capillaries

Back 10

Contrast Agents

Front 11

Strong signals, such as those generated by contrast agents, generate significant ___

Back 11

Harmonics

Front 12

The creation of ___ results from the ___ behavior of microbubbles when sound strikes them

Back 12

Contrast Harmonics
Non-Linear

Front 13

A sound wave is an oscillation of ___

Back 13

Pressure (mmHg)

Front 14

Describe why microbubbles demonstrate non-linear behavior when struck by suond waves of adequate strength?

Back 14

Microbubbles grow and shrink in size - uneven changes

Front 15

When exposed to the high pressure component of a sound wave, a microbubble will ___

Back 15

Shrink

Front 16

When exposed to the low pressure component of a sound wave, a microbubble will ___

Back 16

Grow

Front 17

As microbubbles grow and shrink, a small amount of energy is transferred from the fundamental frequency to the ___

Back 17

Harmonic Frequency

Front 18

The amount of contrast harmonics produced is estimated by a number called the ___

Back 18

Mechanical Index

Front 19

What kind of number is indicated by:
- weaker sound waves (less pressure)
- higher frequency

Back 19

Lower Mechanical Index

Front 20

What kind of number is indicated by:
- stronger sound waves (more pressure)
- lower frequency

Back 20

Higher Mechanical Index

Front 21

Why are microbubbles strong scatterers of sound waves?

Back 21

They vibrate from sound in the 2-4 MHz range, causing even greater resonance

Front 22

Is there a direct (linear) relationship between mechanical index and harmonic creation?

Back 22

No

Front 23

What kind of harmonics does a low mechanical index number create?

Back 23

Low MI (< 0.1) = No Harmonics (just backscatter)

Front 24

What kind of harmonics does an intermediate mechanical index number create?

Back 24

Intermediate MI (0.1 - 1.0) = Moderate Harmonics

Front 25

What kind of harmonics does a high mechanical index number create?

Back 25

High MI (> 1.0) = Significant Harmonics

Front 26

What kind of mechanical index number do the following factors describe:
- no harmonics
- backscatter
- linear behavior
- higher frequency sound
- low beam strength

Back 26

Low Mechanical Index (< 0.1)

Front 27

What kind of mechanical index number do the following factors describe:
- strong harmonics
- resonance
- non-linear behavior
- lower frequency sound
- higher beam strength

Back 27

Intermediate Mechanical Index (0.1 - 1.0)

Front 28

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

Back 28

Highest Mechanical Index (> 1.0)

Front 29

What are two important characteristics of contrast agents?

Back 29

1. The nature of the outer shell
2. The gas that fills it

Front 30

What determines the contrast agent's stability and longevity in the circulatory system?

Back 30

The relationship between the outershell and the internally trapped gas

Front 31

What happens to gas bubbles without outer shells (such as found in agitated saline)?

Back 31

They shrink and quickly dissipate

Front 32

What happens to gass bubbles with rigid outer shells?

Back 32

Rigid outer shells tend to fracture causing bubble disruption

Front 33

When are contrast harmonics created?

Back 33

During Reflection

Front 34

What kind of behavior creates contrast harmonics?

Back 34

Non-Linear Behavior

Front 35

Contrast harmonics are determined by the ___ and ___ of the contrast agent

Back 35

Shell & Gas

Front 36

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?

Back 36

Tissue Harmonics

Front 37

What is a series of compressions and rarefactions called?

Back 37

Sound Wave

Front 38

Sound travels at slightly uneven speeds through soft tissue - ___ through compressions and ___ through rarefactions. This is ___ behavior.

Back 38

Faster
Slower
Non-Linear

Front 39

Does the strength of the harmonic wave grow or shrink as sound travels in tissue?

Back 39

Grows

Front 40

Why do tissue harmonic signals remain distortion free through superficial depths?

Back 40

Fundamental frequencies are distorted by superficial layers, but harmonics develop deeper in tissue (avoiding the distortion causing superficial layers)

Front 41

What behavior describes the relationship between sound beam strength and harmonic creation?

Back 41

Non-Linear

Front 42

Weak sound beams create how much harmonics:
A. None
B. Small Amount
C. Significant Amount

Back 42

A

Front 43

Intermediate sound beams create how much harmonics:
A. None
B. Small Amount
C. Significant Amount

Back 43

B

Front 44

Strong sound beams create how much harmonics:
A. None
B. Small Amount
C. Significant Amount

Back 44

C

Front 45

Sound beams that are ___ likely to create artifacts are ___ likely to create harmonics

Back 45

Least
Most

Front 46

Are harmonics created by grating/side lobes?

Back 46

No, because they are too weak

Front 47

Which are stronger: contrast harmonics or tissue harmonics?

Back 47

Contrast Harmonics

Front 48

In contrast harmonics, what action creates the strongest harmonic signals?

Back 48

Bubble Disruption

Front 49

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

Back 49

Tissue Harmonics

Front 50

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

Back 50

Contrast Harmonics