Doppler Optimization: Doppler controls

Question 1

What are the parts of a doppler waveform creation?

Answer 1

• Doppler beam
• Sample volume
• Angle cursor sets doppler angle.

Question 2

Doppler waveforms shows changes in ______ ______ over time.

Answer 2

Frequency shifts

Question 3

What happens when velocities change?

Answer 3

Frequency shift change.

Question 4

How must your vessel be?

Answer 4

-Must be on axis. (open at each end)

Question 5

How is flow seen when the vessel is on axis?

Answer 5

Flow direction is typically parallel to the walls.

Question 6

if SV is moved along a vessel while you can, what may you need to do?

Answer 6

You may need to change steer directions as vessel changes direction up or down.

Question 7

Why do you want to ster the doppler beam towards the lowest point of the vessel?

Answer 7

It yields better doppler angles so better waveforms.

Question 8

True or False:

Beam steer affects waveform.

Answer 8

True.

Question 9

When is vertical beam steer not a good option?

Answer 9

Vertical beam steer is not good if nearly perpendicular to flow.

Question 10

When is a vertical beam steer a good option?

Answer 10

Vertical beam steer is good if the vessel is already angled.

Question 11

When measuring velocities, why should you use the smallest sv?

Answer 11

To avoid other vessels and flow along the wall.

Question 12

What do larger sv demonstrate?

Answer 12

It shows all velocities across a vessel, including slower velocities along the wall.

Large SV causes spectral broadening, filling in the spectral “window”

Question 13

When should you use a large SV?

Answer 13

When searching for flow in a near occlusion, to find a small channel of flow.

Question 14

What does a sample volume affect?

Question 15

Where should you place the sample volume?

Answer 15

Place sample volume center stream rather than along walls where velocities are lower and flow direction changes are more likely.

Question 16

Where should you place the sample volume in a stenosis?

Answer 16

Place SV at the highest point of velocity (proximal to distal).

Question 17

Where do flow disturbances occur?

Answer 17

Around a curve.

Question 18

Where do velocities naturally increase?

Answer 18

On the outside of the curve.

Question 19

What often occurs on the inside of the curve?

Answer 19

FLow seperation, with reversed flow.

Question 20

How must you steer the sv under a calcification area?

Answer 20

• Steer sv under clacified plaque from each end.
• Use multiple windows to get around the shadow.
  
  • AP Lateral
  • Postero-lateral

Question 21

Describe the echoes from RBC’s?

Answer 21

Echoes are so small that they must be amplified.

Question 22

What is loudness attached to?

Answer 22

Gain.

Question 23

What does gain do?

Answer 23

It affects brightness of each echo in waveform.

Question 24

How should you increase the spectral gain?

Answer 24

Turn spectral gain up until echoes appear outside waveform, then turn down until they disappear for correct gain.

Question 25

What does an overgain result in?

Answer 25

Overestimating velocity slightly.

It also results in a mirror wave “crosstalk”

Question 26

What does an undergain result in?

Answer 26

It may underestimate velocity or make you think the vessel is occluded when its not.

Question 27

How should the scale be set?

Answer 27

Scale should be set so th dopple waveform fills most of the size of the entire scale.

Question 28

Why do you not want the scale to be too high?

Answer 28

It may hide information at the lower levels.

Question 29

A scale too low will cause an artifact called?

Answer 29

Aliasing.

Question 30

How should the baseline be between arteries and veins?

Answer 30

Arteries: Keep baseline low.

Veins: Keep baseline high

but…leave enough room to display reversed flow.

Question 31

Flow ______ is above the baseline.

Answer 31

towards the beam. (positive shift)

Question 32

Flow _____ is below the baseline.

Answer 32

Away from the beam. (negative shift)

Question 33

What is an exception to the flow and their relation with the baseline?

Answer 33

inverted waveform.

Question 34

How is normal arterial flow shown?

Answer 34

Above baseline.

Question 35

How is retrograde arterial flow shown?

Answer 35

Below the baseline.

Question 36

How is normal venous flow seen?

Answer 36

Below the baseline.

Question 37

How is venous reflux seen?

Answer 37

Above the baseline.

Question 38

When should you invert?

Answer 38

Invert as needed to demonstrate a normal or abnormal flow direction. This will assist the intrepreter in noting abnormal flow.

Question 39

What is the doppler angle?

Answer 39

Angle between the doppler beam and flow direction.

Question 40

How do we indicate the flow direction?

Answer 40

We assume flow is parallel to he walls and set the angle cursor parallel to the vessel walls.

Question 41

What will happen If you change the angle correct?

Answer 41

It will not change the doppler waveform, but it will change the velocity measurement.

Question 42

What will happen if you do not set the angle cursor parallel to the walls (or flow)?

Answer 42

The velocity you report will be inaccurate.

Question 43

What doppler angle is appropriate?

Answer 43

Must use a doppler angle that is 60° or less.

Question 44

Why must the doppler be 60° or less?

Answer 44

Because the cosine of the angle in the doppler equation is not linear, so a small error in setting the angle results in a big difference in velocity at angles higher than 60°

Question 45

How to find a 60° angle?

Answer 45

• Beam steer in the direction of the artery.
• Set the angle correct to 60°
• Use “fine steer”, heel and toe probe, and/or find a location in the area of interest where the angle correct is parallel to the walls/flow.

Question 46

Even though you should avoid measuring vleocities on a curve, if you must measure velocities on a curve, what should you do?

Answer 46

Set the middle of the angle cursor parallel to the walls.

Question 47

How do you measure PSV?

Answer 47

Measure highest peak in area of interest unless the patient has arrhythmias, then use most common peak level.

Question 48

How do you measure EDV?

Answer 48

Measure at the END of diastole. (just before systolic upstroke)

Question 49

What is the best order to use doppler controls for velocity measurements?

Answer 49

1. Get long view on axis.
2. Steer the Doppler beam same way as vessel.
3. Place sample volume small and center stream.
4. If you don’t hear and see waveform, gain up.
5. Invert if needed so normal artery flow is above baseline.
6. Set scale so waveform takes up most of the full scale.
7. Change baseline if needed to set scale further. Keep low, but leave room for reversed flow below it.
8. Turn gain up then down to avoid speckles outside waveform.
9. Set angle cursor to 60 degrees and adjust beam steer to make it parallel to walls. You may need to steer it another direction to achieve 60 degrees.
10. If adjusting fine beam steer doesn’t help, heel and toe vessel to make cursor parallel to flow.