Vascular Physics

Question 1

What is known as an increase in the “width” of the spectral waveform or “filling-in” of the normally clear area under the systolic peak?

Answer 1

Spectral broadening

Question 2

What is the doppler shift equation?

Answer 2

Received frequency - transmitted frequency

Question 3

What is the doppler shift equation with cosine?

Answer 3

DSF = (2x op freq) x velocity x cos / C (prop speed)

Question 4

What is the doppler angle?

Answer 4

The angle between the US beam and the blood flow

Question 5

As the doppler angle increases, what happens to the doppler shift?

Answer 5

Decreases

Question 6

As doppler angle increases, what happens to the cosine?

Answer 6

Decreases

Question 7

As cosine increases, what happens to the doppler shift?

Answer 7

Increases

Question 8

What is the proper angle correction in vascular studies?

Answer 8

30-60 degrees

Question 9

For vascular studies, you should not use angles greater than?

Answer 9

60 degrees

Question 10

What is the Nyquist limit?

Answer 10

1/2 PRF - the maximum doppler shift before aliasing

Question 11

PRF must exceed

Answer 11

2x the Nyquist limit

Question 12

How do we eliminate aliasing?

Answer 12

1. Increase PRF scale
2. Decrease the doppler shift
3. Use CW

Question 13

How do we decrease the doppler shift?

Answer 13

1. Decrease the frequency
2. Increase doppler angle

Question 14

What converts multiple frequency shifts into a spectral waveform?

Answer 14

Fast Fourier Transform

Question 15

What is the filling in of the spectral window known as?

Answer 15

Spectral broadening

Question 16

What does colour do to frame rate?

Answer 16

Decreases FR

Question 17

What causes FLASH artifact?

Answer 17

Movement when using power doppler - very sensitive

Question 18

What does a higher sweep speed do to the waveform?

Answer 18

Spreads it out

Question 19

Where do we put the Focus?

Answer 19

At or just after the region of interest (ROI)

Question 20

What change needs to be made when you see very dark red or very dark blue in a vessel? (slide 26)

Answer 20

Lower the PRF scale to see where the higher velocities are

Question 21

If you are lacking flow in a vessel, what adjustment should be made?

Answer 21

1. Decrease the scale FIRST
2. Increase colour gains

Question 22

What type of waveform will be shown with spectral doppler in an artery vs. a vein?

Answer 22

Artery = Pulsatile flow

Vein = Phasic flow