Ch. 20 Optimizing Doppler Imaging

Question 1

When the cosine of a vessel is 90 degrees what happens?

Answer 1

No Doppler shift is created or measured and no color appears in vessel

Question 2

How would you make color appear in a vessel with an angle of 90 degrees?

Answer 2

Create an angle that is not 90 degrees

Question 3

Other than changing the angle is there an alternative action that will make color appear in a vessel?

Answer 3

no, color will never appear in a vessel when directions of flow and sound are perpendicular

Question 4

what single control on an ultrasound system can make color appear throughout the color box in a confetti pattern?

Answer 4

Color gain (Set too high) (Color Confetti)

Question 5

What single control on an ultrasound system can make color disappear on an image?

Answer 5

Color gain (set too low)

Question 6

If there is no color on an image what should be checked first? Second?

Answer 6

First check the angle (90 degree or not) Then check the color gain

Question 7

If the image is sector shaped and has no color what could be the problem?

Answer 7

color gain too low

Question 8

gray scale noise appears throughout the spectrum when what is set too high?

Answer 8

Doppler gain

Question 9

all grey scale will disappear in the image when what is too low?

Answer 9

Doppler gain

Question 10

when Doppler gain is set inappropriately low not only does the noise vanish but so does the what?

Answer 10

meaningful Doppler spectrum

Question 11

whenever the color changes directly from red to blue or vice versa and creates a peculiar color variation what should be considered?

Answer 11

Aliasing

Question 12

in a vessel where red, blue and black are all next to each other what is present

Answer 12

flow reversal

Question 13

If the colors that touch each other in a vessel go around the outside of the color map what is present?

Answer 13

aliasing

Question 14

the most effective way to eliminate aliasing on a color flow image is to

Answer 14

increase velocity scale (PRF)

Question 15

does increasing the scale have any other effects on a color Doppler image?

Answer 15

decreases sensitivity

Question 16

when the scale is increased why does the color in the vein disappear?

Answer 16

Doppler is insensitive to slow flows at that setting, low velocities are lost

Question 17

If color in the vein vanishes as well as the ghosting artifact what has happened?

Answer 17

wall filter

Question 18

wall filters selectively eliminate what?

Answer 18

low frequency doppler

Question 19

Adjustment that is used for both color flow and spectral Doppler?

Answer 19

wall filter

Question 20

the difference between color Doppler and wall filter is that wall filter only alters ___ velocity flows while leaving ___ velocity flows unchanged?

Answer 20

Low, high