Ch. 17 Harmonics and Contrast Agents

Question 1

____________________ imaging is creation of an image from sound reflections at twice the fundamental frequency

Answer 1

Harmonic Imaging is creation of an image from sound reflections at twice the fundamental frequency

Question 2

________________________ frequency is the frequency of sound created by the transducer and transmitted into the body.

Answer 2

Fundamental frequency is the frequency of sound created by the transducer and transmitted into the body

Question 3

____________________ freequency is twice the fundamental (transmitted) frequency

Answer 3

Harmonic Frequency (also called second harmonic frequency) is twice the fundamental (transmitted) frequency

Question 4

Harmonic frequency sound waves arise from ________________________ behavior

Answer 4

Harmonic frequency sound waves arise from nonlinear behavior

Question 5

What does Harmonic Imaging do?

Answer 5

Hamonic Imaging gets rid of low level noise
Most useful in improving poor quality images because harmonic frequency waves undergo less distortion

Question 6

A ____________________________ image is the image created by processing reflections that have the same frequency as the transmitted sound.

Answer 6

A Fundamental Image is the image created by processing reflections that have the same frequency as the transmitted sound

Question 7

A _____________________________ image is the image created by processing reflections that are twice the fundamental frequency.

Answer 7

A Harmonic Image is the image created by processing reflections that are twice the fundamental frequency.

Question 8

Harmonic imaging is most effective when the fundamental image is ____________________ because the harmonic frequency waves undergo less distortion

Answer 8

Harmonic imaging is most effective when the fundamental image is suboptimal because the harmonic frequency waves undergo less distorion

Question 9

Two forms of Harmonics are important in diagnostic sonography what are they?

Answer 9

1. Tissue Harmonics
2. Contrast Harmonics

Question 10

Linear means ________________________ or _________________________.

linear systems respond in an even manner.

Answer 10

Linear means proportional or symmetrical

linear systems respond in an even manner

Question 11

Nonlinear means ___________________ or _____________________________.

A system is nonlinear when it behaves unevenly.

Answer 11

Nonlinear means irregular or disproportionate

Question 12

Linear behavior is _____________________________.

Answer 12

symmetrical

Question 13

Nonlinear behavior is _______________________________.

Answer 13

asymmetrical

Question 14

Energy is converted from Fundamental frequency to the Harmonic frequency; this conversion creates ____________________________ during transmission.

Answer 14

Energy is converted from Fundamental frequency to the Harmonic frequency; this conversion creates Tissue Harmonics during transmission

Question 15

In tissue harmonics sound travels at slightly _______________ speeds through soft tissue.

Answer 15

In tissue harmonics sound travels at slightly uneven speeds through soft tissue

Question 16

A sound wave is a series of ____________________ and ____________________.

Answer 16

A sound wave is a series of compressions and rarefractions

Question 17

In tissue harmonics:

Speed in Compression is ___________________(faster,slower)
Speed in Rarefractions is _____________________(faster,slower)

Answer 17

Speed in Compression is faster

Speed in Rarefractions is slower

Question 18

During _______________ imaging, significant amounts of artifact arise within the first few centimeters of tissue.

Answer 18

During Fundamental imaging, significant amounts of artifact arise within the first few centimeters of tissue

Question 19

Do tissue harmonics exist at extremely superficial depths?

Answer 19

no

Question 20

Tissue harmonics are more likely to be created where?

Answer 20

along the beams main axis

Question 21

Beams that are most likely to create harmonics are least likely to create ____________________

Answer 21

Beams that are most likely to create harmonics are least likely to create artifacts

Question 22

Tissue Harmonics are created _______________ in the tissues

Answer 22

Tissue Harmonics are created deeper in the tissues

Question 23

Tissue Harmonics are created during _________________________

Answer 23

Tissue Harmonics are created during transmission

Question 24

Tissue Harmonics are created by ____________________ behavior in the speed of sound.

Answer 24

Tissue Harmonics are created by nonlinear behavior in the speed of sound

Question 25

Harmonic Imaging reduces artifacts by increasing the ___________________________________

Answer 25

Harmonic Imaging reduces artifacts by increasing the *signal-to-noise ratio*

Question 26

Where is Tissue Harmonics the best?

Answer 26

middle of the image (slightly deep)

Question 27

______________________________ Harmonics is an imaging technique specifically designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections.

Answer 27

*Pulse Inversion* Harmonics is an imaging technique specifically designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections.

Question 28

Reflections contain both _______________________ and ________________________ frequencies

Answer 28

Reflections contain both *fundamental* and *harmonic* frequencies

Question 29

________________________ imaging creates images from the portion of the reflected sound that has the same frequency as the transmitted sound.

Answer 29

*Fundamental Imaging* creates images from the portion of the reflected sound that has the same frequency as the transmitted sound.

Question 30

__________________________ imaging creates images only from the harmonic frequency, which is 2 times the fundamental frequency.

Answer 30

*Harmonic Imaging* creates images only from the harmonic frequency, which is 2 times the fundamental frequency

Question 31

____________________________________ is when two consecutive ultrasound pulses are transmitted down each scan line. The First is a typical pulse, Second is an inverted copy that is "out-of-phase" with the first.

Answer 31

*Pulse Inversion* is when two consecutive ultrasound pulses are transmitted down each scan line. The First is a typical pulse, Second is an inverted copy that is "out-of-phase" with the first.

Question 32

Wherever a compression exists in the first pulse, a ________________________ exists in the second.

Answer 32

Wherever a compression exists in the first pulse, a *rarefaction* exists in the second

Question 33

Pulse Inversion Harmonics separate the __________________________ from the ____________________ frequencies

Answer 33

Pulse Inversion Harmonics separate the *Harmonics* from the *Fundamental* frequencies

Question 34

With Pulse Inversion, a __________________________ and then a ____________________ pulse is transmitted down each scan line

Answer 34

With Pulse Inversion, a *positive* and then a *negative* pulse is transmitted down each scan line

Question 35

The pulse reflections are combined in the ________________________

Answer 35

receiver

Question 36

Two inverse fundamental frequencies are ____________________________ because of destructive interference

Answer 36

Two inverse fundamental frequencies are *canceled out* because of destructive interference

Question 37

The Harmonic portions of the reflections are in phase and interfere _______________________________

Answer 37

The Harmonic portions of the reflections are in phase and interfere *constructively*

Question 38

With Pulse Inversion, only the ______________________ portions of the reflections remain, which form an image with less distortion.

Answer 38

With Pulse Inversion, only the *Harmonic* portions of the reflections remain, which form an image with less distortion.

Question 39

What type of resolution is diminished with pulse inversion?

Answer 39

temporal resolution

Question 40

______________________________________________ is an imaging technique designed to enhance harmonic reflections which contain less distortion while eliminating distorted fundamental reflections. It achieves the same goals as pulse inversion but uses a different engineering approach

Answer 40

*Power Modulation Harmonic Imaging* is an imaging technique designed to enhance harmonic reflections which contain less distortion while eliminating distorted fundamental reflections

Question 41

With Power Modulation, the harmonics are extracted by sending one ________________ pulse, and one ___________ pulse down each scan line.

Answer 41

With Power Modulation, the harmonics are extracted by sending one *strong* pulse, and one *weak* pulse down each scan line.

Question 42

Temporal Resolution is _________________ due to a decrease in the frame rate during power modulation

Answer 42

Temporal Resolution is *decreased* due to a decrease in the frame rate during power modulation

Question 43

What is the difference between Pulse Inversion and Power Modulation?

Answer 43

one negative and one positive one strong pulse and one weak pulse

Question 44

________________________________, also called microbubbles are gas bubbles encapsulated in a shell.

Answer 44

*Contrast Agents*, also called microbubbles are gas bubbles encapsulated in a shell

Question 45

Contrast agents have a different acoustic fingerprint than ______________ or _______________

Answer 45

Contrast agents have a different acoustic fingerprint than *blood* or *tissue*

Question 46

Microbubbles/Contrast agents are either ________________ or _______________ into the body.

Answer 46

Microbubbles/Contrast agents are either *injected* or *ingested* into the body

Question 47

What do Contrast Agents do?

Answer 47

Contrast Agents create strong reflections that light up blood vessels or other anatomy

Question 48

Contrast Harmonics are created during ___________________ due to ___________________ changes in size of the bubble when exposed to sound beam, what is this called?

Answer 48

Contrast Harmonics are created during *reflection* due to *nonlinear* changes in size of the bubble when exposed to the sound beam, this is called *Resonance*

Question 49

When exposed to the high pressure component of a sound wave aka Compression, the bubble _____________________ and the pressure inside the bubble ____________________.

Answer 49

When exposed to the high pressure component of a sound wave aka *Compression*, the bubble *shrinks* and the pressure inside the bubble *increases*

Question 50

When exposed to the low pressure component of a sound beam Rarefaction, the bubble _____________________

Answer 50

When exposed to the low pressure component of a sound beam *Rarefaction*, the bubble *expands*

Question 51

Bubbles ____________ to a greater extent than they ______________.

Answer 51

Bubbles *expand* to a greater extent than they *shrink*

Question 52

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

Answer 52

The amount of contrast harmonics produced may be estimated by a number called the *Mechanical Index*

Question 53

The numerical value of the mechanical index increases with _______________ frequency sound, and _________________ sound waves.

Answer 53

The numerical value of mechanical index increases with *lower* frequency sound, and *stronger* sound waves

Question 54

MI is _______________ (indirectly, directly, unrelated) related to peak rarefractional pressure

Answer 54

MI is *Directly* related to peak rarefractional pressure

Question 55

Mechanical Index formula:

Answer 55

MI = peak rarefraction pressure divided by square root of frequency

Question 56

Tissue Harmonics: Created during _____________________________ in tissue Occurs __________________________________________ in tissue Results from ______________________ behavior of transmitted sound beam ____________ harmonic signal

Answer 56

Tissue Harmonics: Created during *transmission* in tissue Occurs *as sound propagates* in tissue Results from *nonlinear* behavior of transmitted sound beam *weaker* harmonic signal

Question 57

Contrast Harmonics: Created during _______________________ off of microbubble Occurs only when contrast agents are present and with MI's greater than ___________ Results from ____________________ behavior of microbubble ____________________ harmonic signal

Answer 57

Contrast Harmonics: Created during *reflection* off of microbubble Occurs only when contrast agents are present and with MI's greater than *0.1* Results from *nonlinear* behavior of microbubble *stronger* harmonic signal

Question 58

What nonlinear behavior creates tissue harmonics?

Answer 58

Sound travels faster in compressions and slower in rarefractions

Question 59

What nonlinear behavior creates contrast harmonics?

Answer 59

microbubbles expand to a greater extent than they compress This uneven behavior is called resonance

Question 60

Beams with an intermediate mechanical index

Answer 60

0.1 to 1.0 create a relatively small amount of harmonics

Question 61

Beams with a high mechanical index

Answer 61

greater than 1.0 create substantial harmonic signals. Bubble disruption is an ex of extreme nonlinear behavior, which creates very strong harmonic reflections.

Question 62

___________sound beams do not create harmnincs because the microbubbles expand and contract evenly in a linear fashion

Answer 62

Low mechanical index

Question 63

Two characteristics of contrast agents are important:

Answer 63

the nature of the outer shell(gas bubbles without shells such as agitated saline shrink and quickly vanish as the gas dissolves in blood) the gas that fills the microbubble(smaller gas molecules are more likely to leak through the shell and shrink the bubble. Large gas molecules find the shell less permeable and remain trapped within the bubble)