Harmonics & Contrast

Question 1

Sending out one frequency and getting 2 back

Answer 1

harmonics

Question 2

Wave distortion depends on these 3 things

Answer 2

1. Intensity of the beam
2. Distance travelled
3. Type of tissue

Question 3

Why don’t grating lobes harmonize?

Answer 3

They are too weak.

Question 4

What is bandpass filtration?

Answer 4

electronic separation of a frequency contained within a bandwidth

Question 5

What is pulse inversion?

Answer 5

Similar to dynamic damping. The inverse of the fundamental pulse is sent out to cancel it without canceling the harmonic signal

Question 6

What are some advantages of harmonics?

Answer 6

Improved lateral resolution, reverberation is reduced, no main bang, grating lobes are eliminated

Question 7

Why does harmonics improve lateral resolution

Answer 7

the harmonic beam is much more narrow

Question 8

How to improve axial resolution that is reduced from the narrower bandwidth/longer pulse?

Answer 8

Pulse inversion

Question 9

how do areas of high density/pressure/stiffness/bulk modulus affect velocity?

Answer 9

increase

Question 10

how do areas of low density/pressure/stiffness/bulk modulus affect velocity?

Answer 10

decrease

Question 11

how do areas of decreased compressibility affect velocity?

Answer 11

increase

Question 12

how do areas of increased compressibility affect velocity?

Answer 12

decrease

Question 13

What are some characteristics of good contrast?

Answer 13

differing Z values, small enough to make it through capillaries and not cause blockages but large enough to reflect echoes, stable enough to make it through the heart several times, can’t cause allergic reaction or embolism

Question 14

100% power with contrast

Answer 14

transient cavitation

Question 15

75% power with contrast

Answer 15

bubbles produce harmonic echoes & increase contrast between the contrast & tissue

Question 16

MI threshold for contrast ultrasound

Answer 16

0.4

Question 17

Another name for coded excitation

Answer 17

B-flow

Question 18

Advantages of B-flow

Answer 18

improved signal to noise ratio, improved frame rate, improved spatial resolution, can scan with a higher frequency

Question 19

Disadvantages of B-flow

Answer 19

hard to determine direction of flow on a still image

Question 20

Digitized encoded pulses for the purpose of improving overall image quality

Answer 20

coded excitation

Question 21

A protein, lipid, or polymer shell encapsulating a gas

Answer 21

contrast

Question 22

Electronic separation of a frequency contained within a bandwidth

Answer 22

bandpass filtration

Question 23

A two pulse technique used to eliminate the fundamental frequency

Answer 23

pulse inversion

Question 24

How are contrast agents administered?

Answer 24

orally and IV

Question 25

Appropriate diameter of contrast agent bubble

Answer 25

7 micrometers

Question 26

What allows blood flow to be visualized in B-flow?

Answer 26

signal to noise ratio

Question 27

What causes wave distortion?

Answer 27

compressibility/density

Question 28

Which portion of the field is most improved with harmonics?

Answer 28

Mid