Ch. 17 Physics: Harmonics and Contrast Agents

Question 1

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

Answer 1

Harmonic imaging

Question 2

Where does harmonic imaging come from?

Answer 2

nonlinear behavior

Question 3

What are the Two forms of harmonics are important in diagnostic sonography?

Answer 3

Tissue Harmonics

Contrast Harmonics

Question 4

Why is harmonic imaging important to poor quality images?

Answer 4

harmonic frequency waves undergo less distortion than fundamental waves, therefore improving poor quality images.

Question 5

What are the Two types of sound beam behavior?

Answer 5

Linear

Nonlinear

Question 6

What is a linear sound beam behavior?

Answer 6

Proportional or symmetrical, responding in an even manner

Question 7

What is nonlinear sound beam behavior?

Answer 7

Irregular or disproportionate, behaves unevenly

Question 8

Harmonic frequency is _____

Answer 8

Nonlinear

Question 9

Energy is transferred from fundamental to harmonic frequency as sound travels through tissue speeding up (compression) and slowing down (rarefaction).

Answer 9

Tissue harmonics

Question 10

A sound wave is a series of ____________ and ___________.

Answer 10

Compressions

rarefactions

Question 11

Sound travels faster during what?

Answer 11

Compressions

Question 12

sound travels slower during what?

Answer 12

Rarefactions

Question 13

In fundamental imaging, artifacts will be present for what two reasons?

Answer 13

The beam is very strong

Many different superficial anatomic
layers distort the sound beam

Question 14

True or false:
Tissue harmonic signals do exist at extremely superficial depths.

Answer 14

False
They do not. They develop deeper in the tissue

Question 15

Harmonics increases the ____________ ratio.

Answer 15

signal-to-noise

Question 16

Where in the sound beam does max harmonics occur?

Answer 16

Mid-field

Question 17

Where in the sound beam do no harmonics occur?

Answer 17

Near and far field

Question 18

The relationship between the sound beam strength and harmonic creation is ________.

Answer 18

nonlinear

Question 19

Weak beams =

Answer 19

no harmonics

Question 20

intermediate beams =

Answer 20

miniscule amount of harmonics

Question 21

Strong beams =

Answer 21

intense harmonics

Question 22

A tiny amount of energy is converted into harmonics from ……

Answer 22

fundamental energy.

Question 23

True or false:
Only the strong central part of the beam will make harmonics.

Answer 23

True

Question 24

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

Answer 24

artifacts.

Question 25

What are the Two imaging techniques that are designed to enhance harmonic reflections?

Answer 25

Pulse inversion harmonics (most common) Power modulation harmonics

Question 26

What separates the fundamental frequency from the harmonic with greater success than filters achieved?

Answer 26

Pulse inversion harmonics

Question 27

An imaging technique specifically designed to utilize harmonic reflections, while eliminating distorted fundamental reflections.

Answer 27

Pulse inversion harmonics

Question 28

In pulse inversion harmonics, what is the second pulse sent down the scan line?

Answer 28

an inverted copy of the original.

Question 29

What happens when Fundamental signals destructively interfere?

Answer 29

cancel each other out

Question 30

How do Harmonic signals interfere with pulse inversion harmonics?

Answer 30

constructively

Question 31

What is the disadvantage of pulse inversion harmonics?

Answer 31

decreased temporal resolution and frame rate

Question 32

another technique to isolate the harmonic sound beam.

Answer 32

Power modulation harmonics

Question 33

What are the two beams that are sent out for power modulation harmonics?

Answer 33

A weak beam A beam 2x as strong

Question 34

During reception of the power modulation harmonic, reflections from the strong pulse are ________________________ from the second reflection

Answer 34

doubled and subtracted

Question 35

Power modulation harmonics ___________ frame rate and temporal resolution.

Answer 35

decreases

Question 36

also known as microbubbles (encapsulated air)

Answer 36

Contrast agents

Question 37

Because of their different acoustic properties they create strong reflections that “light up” the structure being imaged.

Answer 37

contrast agents

Question 38

How are contrast agents taken?

Answer 38

injected or swallowed

Question 39

What are the 5 requirements of contrast agents?

Answer 39

Safe Metabolically inert Long lasting Strong reflector of ultrasound Small enough to pass through capillaries

Question 40

When sound interacts with contrast agents, much __________ harmonics are created.

Answer 40

stronger

Question 41

How do microbubbles act when struck by a sound wave?

Answer 41

non linear

Question 42

Contrast harmonics are created during ......

Answer 42

reflection

Question 43

True or false : Contrast harmonic signals are weaker than tissue harmonics

Answer 43

False They are stronger

Question 44

a number that allows for the estimation of contrast harmonics that will be created by a sound beam.

Answer 44

Mechanical index (MI)

Question 45

What two factors does mechanical index rely on?

Answer 45

Frequency Peak rarefaction pressure

Question 46

MI and harmonic production increases with:

Answer 46

Lower frequency sound Stronger sound waves (substantial pressure variation)

Question 47

The contrast agents need either_________ or _________to create high Mechanical Indices.

Answer 47

Time or strength

Question 48

MI and frequency are __________ related.

Answer 48

inversely

Question 49

MI and Peak Negative Pressure are _____________ related.

Answer 49

Directly

Question 50

represents the potential amount of contrast harmonics produced.

Answer 50

MI

Question 51

Low mechanical index sound beams means

Answer 51

no harmonics MI less than 0.1

Question 52

Intermediate mechanical index means

Answer 52

relatively small amount of harmonics MI 0.1 to 1.0

Question 53

High mechanical index means

Answer 53

substantial harmonic signals MI greater than 1.0 Very strong harmonic reflections from bubble disruption

Question 54

determines the behavior of the bubbles (linear or nonlinear)

Answer 54

MI

Question 55

A low MI creates what kind of behavior?

Answer 55

Linear