Ch 17: Harmonics & Contrast Agents

Question 1

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

Answer 1

harmonic imaging

Question 2

The transmitted frequency is called the __ frequency.

Answer 2

fundamental

Question 3

The __ frequency is twice the transmitted frequency.

Answer 3

harmonic

Question 4

Harmonic frequency sound waves arise from __ behavior.

Answer 4

nonlinear

Question 5

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

Answer 5

harmonic image

Question 6

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

Answer 6

fundamental image

Question 7

What two forms of harmonics are important in diagnostic sonography?

Answer 7

1. tissue harmonics

2. contrast harmonics

Question 8

This kind of behavior is proportional and symmetrical.

Answer 8

linear

Question 9

This kind of behavior is irregular and disproportionate.

Answer 9

nonlinear

Question 10

T/F? Tissue harmonics happens during transmission.

Answer 10

true

Question 11

The __ of the harmonic wave grows as sound travels in tissue.

Answer 11

strength

Question 12

Tissue harmonic signals do not exist at __ depths.

Answer 12

extremely superficial

Question 13

The use of harmonics __ the signal-to-noise ratio.

Answer 13

increases

Question 14

T/F? The relationship between sound beam strength and harmonic creation is linear.

Answer 14

FALSE, nonlinear

Question 15

Beams that are most likely to create harmonics are least likely to create __.

Answer 15

artifacts.

Question 16

T/F? Tissue harmonics are primarily created along the beam’s side lobes.

Answer 16

FALSE, along the beam’s main axis

Question 17

This is an imaging technique specifically designed to utilize harmonic reflections while eliminating distorted fundamental reflections.

Answer 17

pulse inversion harmonics

Question 18

With pulse inversion harmonics, a __ pulse is followed by a __ pulse.

Answer 18

typical, inverted

Question 19

In pulse inversion harmonics, the typical and inverted pulse reflections are combined in the…

Answer 19

receiver.

Question 20

The disadvantage of pulse inversion harmonics is that…

Answer 20

the frame rate is halved and the temporal resolution is reduced.

Question 21

This is an imaging technique specifically designed to augment harmonic reflections.

Answer 21

power modulation harmonics

Question 22

With power modulation harmonics, a __ pulse is followed by a __ pulse.

Answer 22

typical, 2x as strong

Question 23

The disadvantage of power modulation harmonics is that…

Answer 23

the frame rate is halved and the temporal resolution is reduced.

Question 24

These are gas bubbles encapsulated in a shell.

Answer 24

contrast agents aka microbubbles

Question 25

Contrast agents must be...

Answer 25

1. safe 2. metabolically inert 3. long lasting 4. strong reflector 5. capillary small

Question 26

T/F? Contrast harmonics are created during transmission.

Answer 26

FALSE, reflection

Question 27

The uneven behavior of microbubbles in a sound beam is called...

Answer 27

resonance.

Question 28

When exposed to the high pressure component of a sound wave (compression), the microbubble __.

Answer 28

shrinks

Question 29

When exposed to the low pressure component of a sound wave (rarefaction), the microbubble __.

Answer 29

expands

Question 30

What keeps the microbubble from shrinking very much?

Answer 30

internal pressure

Question 31

What keeps the microbubble from expanding very much?

Answer 31

nothing!

Question 32

T/F? Bubbles shrink to a greater extent than they expand.

Answer 32

FALSE, the opposite

Question 33

This is number that estimates the amount of contrast harmonics produced.

Answer 33

mechanical index aka MI

Question 34

The MI depends on the...

Answer 34

1. transmission frequency | 2. rarefaction pressure

Question 35

The MI increases with...

Answer 35

1. lower frequency sound | 2. stronger sound waves

Question 36

Why are microbubbles strong scatterers of sound waves?

Answer 36

Because they resonate when exposed to sound in the 2 to 4 MHz range.

Question 37

Low MI does not create harmonics because...

Answer 37

the microbubbles expand and contract evenly in a linear fashion.

Question 38

When the MI is less than __, bubbles create only backscatter.

Answer 38

0.1

Question 39

When the MI is __, bubbles create relatively small amounts of harmonics.

Answer 39

0.1 to 1.0

Question 40

When the MI is __, bubbles create substantial harmonics.

Answer 40

greater than 1.0

Question 41

What are the important characteristics of contrast agents when used with harmonic imaging?

Answer 41

1. the nature of the outer shell | 2. the gas that fills the bubble

Question 42

The relationship between the bubble's shell and internal gas determines its...

Answer 42

stability and longevity.

Question 43

Which is stronger: tissue or contrast harmonics?

Answer 43

contrast harmonics by a lot

Question 44

Contrast harmonics are created during...

Answer 44

reflection.

Question 45

Contrast harmonics are created by __ behavior.

Answer 45

nonlinear

Question 46

Contrast harmonics are related to the __ index.

Answer 46

mechanical

Question 47

Low MI creates linear behavior and...

Answer 47

no harmonics.

Question 48

Higher MI creates nonlinear behavior and...

Answer 48

some harmonics.

Question 49

Very high MI creates bubble disruption and...

Answer 49

very strong harmonics.