Doppler Pt 2

Question 1

when color obscures the gray scale display of soft plaque because resolution of color doppler is lower than gray scale

Answer 1

blooming artifact occurs

Question 2

clutter is reduced by

Answer 2

increasing PRF or wall filter or reducing color gain

Question 3

___ persistence levels should be used to optimize color doppler of cardiac structures

Answer 3

low

Question 4

___ persistence levels should be used for slow flow in levels

Answer 4

higher

Question 5

best way to optimize color

Answer 5

use a smaller color box for higher frame rate–fewer scan lines needed

Question 6

smaller samples = less data to collect and process =

Answer 6

faster frame rate

Question 7

decreased color gain is not related to

Answer 7

flash artifact

Question 8

decreased color scale and filter and increased color priority are related to

Answer 8

flash artifact

Question 9

primary CW advantage

Answer 9

no Nyquist limit

Question 10

frequency and peak doppler shift relationship

Answer 10

direct

Question 11

resistance and velocity increase at

Answer 11

arterial stenosis

Question 12

PQ at PRF of 5000/s, max doppler frequency that can be detected =

Answer 12

2.5 kHz

Question 13

Nyquist limit =

Answer 13

PRF / 2

Question 14

increased threshold/priority will display

Answer 14

more color flow (more low velocity flow)

Question 15

decreasing scale and filter settings will allow for display of

Answer 15

lower velocity flow

Question 16

increasing gain will

Answer 16

amplify doppler shifts detected and increase color flow

Question 17

if reflector and sound source are moving at the same speed and direction

Answer 17

doppler shift will not be detected

Question 18

if stenosis/blockage reduces lumen to 1/2 normal area, velocity of flow at stenosis must ____ to maintain flow rate

Answer 18

double

Question 19

Primary PW advantage

Answer 19

range resolution

Question 20

In PW, how often blood flow is sampled is determined by

Answer 20

PRF

as PRF increases, pulses are emitted at a faster rate which leads to faster sampling

Question 21

assesses data from multiple sampling sites and produces a display representing mean flow velocities–color

Answer 21

autocorrelation

Question 22

used to process PW

Answer 22

FFT

Question 23

used to assess and describe pressure gradients in blood flow

Answer 23

Bernoulli equation

Question 24

doppler shift exceeding ____ causes aliasing

Answer 24

Nyquist limit

Question 25

velocity and doppler shift relationship

Answer 25

direct

Question 26

sample size and frame rate relationship

Answer 26

inverse

Question 27

____ to change course of the vessel across image and allow vessel to accurately display a single color

Answer 27

heel to toe

Question 28

to demonstrate more cardiac cycles on PW

Answer 28

decrease sweep speed

Question 29

has 2 separate elements so is not limited to pulse echo parameters like PRF and Nyquist

Answer 29

CW

Question 30

changing color flow doppler velocity scale alters

Answer 30

PRF

Question 31

increasing transmit frequency increases risk of

Answer 31

aliasing

Question 32

power doppler disadvantages

Answer 32

slow frame rates and flash artifact

Question 33

refers to how long color is displayed on screen for each doppler shift, produces smoother image

Answer 33

persistence

Question 34

____ persistence will ____ the amount of time a color pixel is displayed over an area

Answer 34

increasing | increase

Question 35

low persistence should be used for

Answer 35

fetal cardiac assessment

Question 36

cross talk

Answer 36

type of mirror image artifact

Question 37

of pulses per scan line increases, color packet size ___, frame rate ___

Answer 37

increase | decreases

Question 38

increased when evaluating venous flow

Answer 38

color priority

Question 39

used in bidirectional doppler systems

Answer 39

quadrate phase detection

Question 40

element ___ has no effect on doppler shift

Answer 40

width

Question 41

element ___ determines doppler frequency

Answer 41

thickness

Question 42

(2 x blood velocity x transducer frequency x cos (angle)) / speed of sound in ST =

Answer 42

doppler shift

Question 43

as velocity increases pressure

Answer 43

drops

Question 44

most common doppler artifact

Answer 44

aliasing

Question 45

to best display arrhythmia

Answer 45

reduce sweep speed

Question 46

refers to # of pulses / scan line used for doppler imaging

Answer 46

ensemble length

Question 47

color doppler has ___ temporal res

Answer 47

worst

Question 48

M-mode has ___ temporal res

Answer 48

best

Question 49

cos and calculated velocity relationship

Answer 49

inversely proportional

Question 50

peak velocity of 60 cm/s is obtained at 0 degrees, at 60 degrees the actual velocity is

Answer 50

120 cm/s

Question 51

increasing PRF will reduce ___ while increasing ___

Answer 51

aliasing | appearance of range ambiguity

Question 52

increased wall filter will

Answer 52

reduce low level echoes

Question 53

____ can be used to increase # of scan lines in color

Answer 53

persistence

Question 54

increased frequency will reduce ____ and increase ____

Answer 54

range ambiguity | aliasing

Question 55

blood flow that varies with respiration

Answer 55

phasic

Question 56

5 MHz CW and 5 MHz PW are fired at the same time, which will produce spectral wave first?

Answer 56

they will produce spectral wave at the same time | speed of sound in the body is the same for both transmitted waves

Question 57

increased hematocrit = increase viscosity = thicker blood =

Answer 57

decreased flow velocities

Question 58

decreased hematocrit = decreased viscosity = thinner blood =

Answer 58

increased flow velocities

Question 59

avoid aliasing by

Answer 59

``` reducing imaging depth increase PRF (by increasing doppler velocity scale) decrease transmit frequency increase doppler incidence angle shift 0 baseline use CW doppler ```