Chapter 3- Physician Principles of Doppler

Question 1

What is the 13 second rule?

important

Answer 1

The amount of time it takes for US to travel 1 centimeter into tissue and 1 cm back to transducer.

Question 2

What is the average speed of US through soft tissue?

Answer 2

1540 m/sec

Question 3

What is the Doppler shift?

• Remember that when an ultrasound wave this a moving target like blood, the reflected sound waves are changed.**

Answer 3

the difference between the wave frequency directed into tissues and what returns?

Question 4

What is the idea Doppler angle for vascular:

Answer 4

45-60 degrees ** NO MORE THAN 60**

Question 5

What is the angle of insonation?

Answer 5

The angle that the US beam strikes the blood cells ( where we put the sample volume/gate and how we angle the Doppler angle)

Question 6

Two piezo-electric crystals are sent out.

Answer 6

CW Doppler **like ABI’s*

Question 7

What is the main negative about CW Doppler?

Answer 7

No depth resolutation. If there is a stenosis its hard to know EXACTLY where it comes from. Its an estimation.

Question 8

Analog CW Doppler is more of an average- it is more of an estimation
TRUE FALSE

Answer 8

True

Question 9

Fast Fourier Transfer displays what?

Answer 9

ALL frequencies moving through sample area.

Question 10

Fast Fourier Transfer (FFT) is an example of what kind of continuous wave?

analog or digit

Answer 10

Digital

*Think digital has more detail.

Question 11

Pulsed wave is a primary technique we use often. How many crystals are activated to create the US wave?

Answer 11

1

*Think pulse wave is the #1 technique we use

Question 12

Using the 13 second rule, how long would it take to obtain a signal from 3 cm deep in the tissue?

Answer 12

39 ( 13 x 3)

Question 13

PRF stands for AND what is it?

Answer 13

Pulse repetition frequency, number of pulses per unit time that are sent into tissue

Question 14

What is the nyquist limit and what might occur if this is exceeded?

Answer 14

Nyquist limit is a Doppler shift frequency is greater than 1/2 the PRF

Question 15

What can we do to fix aliasing?

Answer 15

decrease the PRF ( due to nyquist limit)

Question 16

Power Doppler uses FFT that analyzes ALL the frequencies moving through the sample area
True or False

Answer 16

True

Question 17

We don’t know exact what direction the blood cells are moving through the vessel therefore we must angle (Parallel/perpendicular) the vessel.

Answer 17

Parallel.

Question 18

Why does smaller sample volumes yield a weaker signal?

Answer 18

because its sampling less and there is like RBC to sample.

Question 19

What is the negatives of a larger sample volume?

Answer 19

may include small vessels and spectral broadening may occur.

Question 20

What is the appropriate sample volume?

** Important**

Answer 20

1.5-2.5 mm

Question 21

When the sample volume is narrower, is it likely spectral broadening will occur?

Answer 21

not likely. The narrower the sample volume the less likely for spectral broadening.

Question 22

In areas of stenosis , spectral broadening will occur indicating disorganized flow.

True / False

Answer 22

True

Question 23

There is always disease associated with spectral broadening

yes or no?

Answer 23

NO. Usually spectral broadening can indicate disturbed flow, but sometimes the spectral broadening can happen when there’s a large sample volume .

Question 24

Why does Continuous wave Doppler always have a full spectral window?

Answer 24

the sample volume is large

Question 25

The deeper the vessel were trying to listen to is, the ( Longer/shorter) the pulse.

Answer 25

Longer

further away means longer pulse.

Question 26

The further deeper the vessel is to listen to the more _____ the frame rate will be. Decreased/increased

Answer 26

Decreased

Question 27

Are frame rate and depth of vessel inversely related or directly?

Answer 27

Inversely

Increased depth=lower frame rate

Decreased depth=higher frame rate.

Question 28

What is the definition of pulsed repetition frequency (PRF)

Answer 28

the number of pulse listen cycles per unit time

Question 29

When does the mirroring artifact occur?

Answer 29

With high gain settings.

Question 30

What is helical flow patterns caused by and where is it often seen?

Answer 30

this is caused by blow flow spiraling up in the artery. Seen at carotid bulb.