Ch. 1 Physical Principles/ Doppler Imaging

Question 1

___: the difference between transmitted frequency and received frequency

Answer 1

Doppler shift

Question 2

What are some factors that can cause spectral broadening?

Answer 2

-disease
-large sample volume
-can occur in normal vessels

Question 3

Will PW or CW Doppler will always have spectral broadening and why?

Answer 3

CW because of the large sample volume (remember CW samples the whole length of the beam)

Question 4

___: the filling in of the spectral window

Answer 4

Spectral broadening

Question 5

___: number of cycles per second

Answer 5

Frequency

Question 6

___: the number of pulses the US beam sends into the body each second

Answer 6

Pulse repetition frequency (PRF)

Question 7

___: the time it takes the US beam to travel 1cm into the body and back

Answer 7

13 microsecond rule

Question 8

What is the Doppler equation when solving for velocity

Question 9

If this is the Doppler equation when solving for velocity what does each part represent and what is directly related

Answer 9

V= velocity
C= speed of sound in soft tissue (1540)
Fo= transducer freq
Cos 0= angle of incidence
Df= Doppler shift freq

Df and C are directly related with velocity

Question 10

What is the Doppler equation when solving for Doppler freq

Question 11

___: digital technique used to process both PW and CW Doppler

Answer 11

Fast Fourier transfer (FFT)

Question 12

when the transducer has increased freq what happens to pen and res

Answer 12

increases freq= increased res, decreased pen

Question 13

decreased freq= ___ res and ___ pen

Answer 13

decreased freq= decreased res, increased pen

Question 14

what is the optimal angle of incidence for gray scale imaging

Answer 14

90 degrees

Question 15

what is the optimal angle of incidence for doppler imaging

Answer 15

60 or less

Question 16

which of the following has spectral broadening

Answer 16

the bottom one

Question 17

how are frame rate and depth related

Answer 17

inversely, meaning increased depth = decreased frame rate

Question 18

what artifact does this image show

Answer 18

aliasing

Question 19

___: the ability of the system to properly display flow

Answer 19

Nyquist limit

Question 20

what happens when PRF is greater than 1/2 the nyquist limit

Answer 20

aliasing

Question 21

what are some things you can do to fix aliasing

Answer 21

-increase scale
-lower baseline
-lower freq
-use CW doppler (doesn't alias)

Question 22

what is the speed of US through soft tissue

Answer 22

1540 m/sec

Question 23

what are the two types of CW doppler

Answer 23

-analog
-digital or spectral

Question 24

what are the benefits of CW doppler

Answer 24

does not alias

Question 25

what are the cons of CW doppler

Answer 25

large sample volume (entire course of US beam)

Question 26

when looking at this image of the color scale, which color is towards the transducer and which is away

Answer 26

top is always towards so in this case red
bottom is always away so in this case blue

Question 27

steps to determine flow direction with color doppler

Answer 27

1. locate the top two corners of color box
2. draw line straight down, whichever is outside of the box is the side of your transducer
3. you will them look at your scale to determine if flow is moving towards or away from your transducer

Question 28

is this flow moving towards or away from your transducer

Answer 28

toward

Question 29

which vessel is moving toward the transducer and which is moving away?

Answer 29

SFA= toward
SFV= away

Question 30

is the flow in this vessel moving toward or away from your probe?

Answer 30

toward

Question 31

true or false: the vessel on the top is moving away from your transducer

Answer 31

true

Question 32

how to determine flow direction with no color

Answer 32

1. draw a line straight down crossing through sample gate (some machines do this already)
2. Make the letter H with spectral gate
3. find where the lines intersect on the top and that is the side your probe is on

TIP: always remember + is towards - is away

Question 33

which direction is this flow going?

Answer 33

away

Question 34

what direction is this flow traveling?

Answer 34

toward