Lesson 21 (Part 1)

Question 1

What will happen tp the frequency if you are scanning a moving object like blood?

Answer 1

The returning frequency will not be the same

Question 2

Doppler effect

Answer 2

Change in frequency caused by the motion of a source, reflector or receiver

Question 3

What is the source of the doppler effect in ultrasound?

Answer 3

The transducer

Question 4

What is the reflector of the doppler effect in ultrasound?

Answer 4

The tissue/RBC

Question 5

What is the receiver of the doppler effect in ultrasound?

Answer 5

The transducer

Question 6

What is changes in frequency caused by?

Answer 6

The motion of the reflector

Question 7

Dopple shift

Answer 7

The change in frequency

- delta f or fD

Question 8

What does the change in frequency depend on?

Answer 8

Whether the object is moving closer or farther away

Question 9

What is the formula for Doppler shift?

Answer 9

fD = fR-fT
fD = doppler shift 
fR = received 
fT = transmitted

Question 10

What is the formula for delta F?

Answer 10

kHz

Question 11

What does the frequency do when the doppler shift gets closer together?

Answer 11

It increases

- positive shift

Question 12

What does the frequency do when the doppler shift gets farther apart?

Answer 12

It decreases

- negative shift

Question 13

What happens to the blood in a positive shift?

Answer 13

Blood moves towards the transducer

Question 14

What happens to the blood in a negative shift?

Answer 14

Blood moves away from the transducer

Question 15

What does it mean if you have 2 different colours in a doppler shift?

Answer 15

It is showing blood moving in two different directions

Question 16

What do we do in Doppler? (4)

Answer 16

1. We fire a particular frequency
2. We measure the frequency that returns
3. We figure out the Doppler shift
4. We can calculate how fast an object is moving

Question 17

What happens when the doppler shift goes up?

Answer 17

Speed goes up

Question 18

What happens when the doppler shift goes down?

Answer 18

Speed goes down

Question 19

What does changing the frequency affect?

Answer 19

It wont affect the rate of velocity
- we do not directly affect the velocity by changing the frequency (the speed doesnt change because we are changing the probe)

Question 20

What is the doppler shift?

Answer 20

Is the difference between the sent and returning frequencies of the sound wave

Question 21

How can we affect the Doppler shift?

Answer 21

By changing the frequency

Question 22

What do we use the Doppler shift to calculate?

Answer 22

Velocity

Question 23

What are examples of the doppler effect? (4)

Answer 23

1. Police speed detectors
2. Weather forecasting
3. Door openers
4. Burglar alarms

Question 24

How is our probed compared to the blood flow?

Answer 24

Parallel to it

Question 25

What happens if the angle of interrogation is non-zero?

Answer 25

Less Doppler shift will occur

Question 26

How do we fix the lesser doppler shift?

Answer 26

By incorporating cos (cosine)

Question 27

Doppler angle

Answer 27

Angle between the sound beam and the vessel

Question 28

What does doppler shift depend on?

Answer 28

The cosine of the doppler angle

Question 29

What is the formula for fD with cos?

Answer 29

fD = 2fvcos/c
fD = doppler shift 
f = fundamental frequency 
v = velocity 
cos = angle 
c = propagation speed

Question 30

What is the formula for v with cos?

Answer 30

v = 77fD/fcos
v = velocity 
fD = doppler shift 
f = fundamental frequency 
cos = angle