Physics Ch. 17

Question 1

Creation of an image from sound reflections at twice the frequency of the transmitted sound

Answer 1

harmonic imaging

Question 2

Sound created by the transducer and transmitted into the body

Answer 2

fundamental frequency

Question 3

twice the fundamental frequency

Answer 3

harmonic frequency

Question 4

Harmonic frequency sound waves arise from

Answer 4

non-linear behavior

Question 5

Harmonic imaging is most useful in __________. Why?

Answer 5

improving poor quality images. Frequency waves undergo less distortion than fundamental waves

Question 6

What are the two forms of harmonics

Answer 6

tissue, contrast

Question 7

proportional, symmetrical, even

Answer 7

linear behavior

Question 8

disproportionate, irregular, uneven

Answer 8

nonlinear behavior

Question 9

Harmonic frequency sound arises from ______ behavior

Answer 9

nonlinear

Question 10

As sound waves travel in the body, a minuscule amount of energy is converted from the fundamental frequency to the harmonic frequency

Answer 10

tissue harmonics

Question 11

Tissue harmonics occur during

Answer 11

transmission

Question 12

Sound is a

Answer 12

series of compression and rarefactions

Question 13

Speed travels ____ through compressions and _____ through rarefactions

Answer 13

faster, slower

Question 14

As sound travels into the tissue, a small amount of energy is transferred from the fundamental frequency to

Answer 14

the harmonic frequency

Question 15

The strength of the harmonics wave ______ as sound travels in tissue

Answer 15

grows

Question 16

Significant amount of artifact within the first few centimeters of tissue is due to

Answer 16

1. strong beam 2. superficial anatomic layers distort the beam

Question 17

Tissue harmonic signals _____ exist at extremely ______ depths, the signal does not distort- the develop in deeper tissue

Answer 17

do not, superficial

Question 18

The use of harmonics ______ the signal-to-noise ratio

Answer 18

increase

Question 19

Weak sound beams _____ create tissue harmonics. Intermediate sound beams create ______ of tissue harmonics. Strong sound beams create ______ tissue harmonics

Answer 19

do not, tiny amount, significant

Question 20

Harmonics are produced along the _____ beam

Answer 20

main

Question 21

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

Answer 21

create artifacts

Question 22

Tissue harmonics are ____ present as sound leaves the transducer, they are created _____ in the tissues

Answer 22

not, deeper

Question 23

Tissue harmonics is created during

Answer 23

transmission

Question 24

Tissue harmonics is _____ in the speed of sound

Answer 24

nonlinear behavior

Question 25

Imaging technique designed to utilize harmonic reflections, which are distortion free, while eliminating distorted fundamental reflections

Answer 25

pulse inversion harmonics

Question 26

This technique separates the harmonics from the fundamental frequencies more successfully

Answer 26

pulse inversion harmonics

Question 27

How does pulse inversion harmonics work

Answer 27

2 pulses are transmitted down each scan line. First pulse is normal, second is inverted. They interfere destructively and cancel each other out and all that is left is harmonic frequency

Question 28

Pulse inversion harmonics: time frame= / frame rate= / temporal resolution= / spatial resolution=

Answer 28

doubled, halved, reduced, improved

Question 29

Achieves the same goals as pulse inversion, but uses a different engineering approach

Answer 29

power modulation harmonics

Question 30

How does power modulation harmonics work

Answer 30

2 pulses are sent down each scan line, second pulse is twice the strength of the first one. first (weaker) does not contain harmonics and the second (stronger) contains harmonics

Question 31

Power modulation harmonics: frame rate= / temporal resolution=

Answer 31

halved, reduced

Question 32

microbubbles, gas bubbles encapsulated in a shell

Answer 32

contrast agents

Question 33

contrast agents/microbubbles are designed to

Answer 33

create strong reflections that light up blood chambers/vessels

Question 34

What are the two important characteristics of contrast agents

Answer 34

1. nature of the outer shell 2. gas that fills the microbubble

Question 35

An ultrasound pulse interacts with contrast agents, MUCH STRONGER harmonics are generated

Answer 35

contrast harmonics

Question 36

contrast harmonics are created because the

Answer 36

microbubbles act in a nonlinear manner when struck by sound waves

Question 37

Contrast harmonics are created during

Answer 37

reflection

Question 38

What is the nonlinear/uneven behavior in bubble size called

Answer 38

resonance

Question 39

the microbubble expands during

Answer 39

rarefaction (low pressure)

Question 40

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

Answer 40

mechanical index

Question 41

The MI depends on

Answer 41

the frequency of the transmitted sound and rarefaction pressure of the sound wave

Question 42

The numerical value of the MI and harmonic production increases with

Answer 42

1. lower frequency sound 2. stronger sound waves

Question 43

Lower MI has

Answer 43

small pressure variation, higher frequency

Question 44

Higher MI has

Answer 44

large pressure variation, lower frequency

Question 45

Low MI (less than 0.1) creates linear behavior so

Answer 45

no harmonics

Question 46

Higher MI (0.1-1.0) creates non linear behavior so

Answer 46

some harmonics

Question 47

Highest MI (greater than 1.0) creates no linear behavior so

Answer 47

bubble disruption and strongest harmonics

Question 48

Contrast harmonics created by microbubbles are

Answer 48

much stronger than tissue harmonics