SPI review 5

Question 1

flow towards the transducer

Answer 1

increased flow

Question 2

flow away from trans

Answer 2

decreased flow

Question 3

the doppler shift ranges from

Answer 3

20-20000Hz

Question 4

the process by which the doppler freq (shift) is extracted from the trans freq

Answer 4

demodulation

tran freq high, doppler freq is low

Question 5

doppler shift = rcvd freq - transmitted freq

Answer 5

FD = FR - FE

Question 6

doppler equation

Answer 6

doppler shift=2xreflector speedxincident freqxcos(angle)/prop speed

Question 7

doppler shift is directly related to the

Answer 7

red blood cell speed

freq of transducer

cosine of the angle between flow and the sound beam

Question 8

doppler shift is inversly related to

Answer 8

the speed of the sound in the medium

Question 9

what does the 2 in the doppler equation represent

Answer 9

double doppler shift, 1st occurs when the sound stikes the cell the 2nd the moving blood cell reflecting the wave back to the transducer

Question 10

in order to accuratley determine velocity

Answer 10

the angle between the directions of flow and sound beam must be known

Question 11

doppler measures velocity not

Answer 11

speed

Question 12

velocity is

Answer 12

magnitude and direction

Question 13

doppler freq depends on direction. The magnirude of shift depends upon the

Answer 13

cosine of the angle between the sound beam and the direction of motion

Question 14

angle is
0
60
90

the cosines are

Answer 14

1
0.5
0

Question 15

doppler shift is inversly related to

Answer 15

the speed of sound in a medium

Question 16

non coherent processing is used with

Answer 16

unidirectioinal dopper

Question 17

a basic doppler system (non or unidirectional dopper) that simply identifies the blood flow by the presence of

Answer 17

a freq shift, it does not distinguish blood flowing towards or away from trans

Question 18

more sophisticated doppler systtem which distinguishes

Answer 18

flow towards and away from trans

Question 19

bidirectional doppler distiguishes to and from trans by

Answer 19

the measurment of positive and negative doppler shifts

Question 20

____ __________ is used in bidirectional doppler

Answer 20

phase quadrature

Question 21

number of crystals in continuous wave trans

Answer 21

two

one is transmitting and one is receiving

Question 22

advantage of continuous wave dopper

Answer 22

able to measure very high velocities accurately

Question 23

disadvantage of continuous wave dopper

Answer 23

range ambiguity-echoes arise from entire length of overlap between the transmit and rcv beams

Question 24

range means

Answer 24

depth

Question 25

other advantages of continuous wave doppler

Answer 25

higher sensitivity and ease in detecting small doppler shifts

Question 26

pulsed wave doppler number of crystals

Answer 26

one crystal that alternates between sending and rcving

Question 27

advantages of pulsed wave doppler

Answer 27

range resolution aka range specificity freedom from range ambiguity echoes arise only from the area o interrogation, the sample volume or gate. we adjust the receive gate

Question 28

disadvantage of pulsed wave doppler

Answer 28

aliasing, errors in measuring high velocities

Question 29

imaging and pulsed doppler can be performed with a single crystal trans. Simultanious imaging and doppler is know as

Answer 29

duplex ultrasound

Question 30

high velocities appear negative. with pulsed doppler, high velocity measurements are inaccurate if the pulsed doppler sampling rate (PRF) is too low in comparison to measured blood velocity

Answer 30

aliasing

Question 31

eliminating aliasing

Answer 31

improves the ability to measure the max velocity with doppler

Question 32

the doppler freq at which aliasing occurs, = to 1/2 the PRF.

Answer 32

nyquist freq

Question 33

nyquist limit (kHz) =

Answer 33

(kHz) = PRF/2

Question 34

deeper samples are more

Answer 34

likely to have aliasing

Question 35

w/ _____ freq transducers, aliasing is more likely to occur

Answer 35

higher

Question 36

5 ways to eliminate aliasing

Answer 36

adjust the scale (increases the PRF and Nyquist limit) get trans w/ lower freq get a new window/view with shallower sample volume switch to continuous wave doppler adjust baseline(only appears gone)

Question 37

smaller sample volumes (gates) create doppler spectra with ____ _____ ______

Answer 37

larger cleaner envelopes

Question 38

larger sample volumes (gates) create doppler spectra with ____ _____

Answer 38

smaller envelopes (spectral broadening)

Question 39

x axis on doppler spectrum

Answer 39

time

Question 40

y asxis of doppler spectrum is

Answer 40

doppler shift or velocity

Question 41

doppler shift and trans freq are _____ related

Answer 41

directly

Question 42

with a 7MHz probe doppler shift is 3000Hz, what will the shift be with a 3.5MHz probe

Answer 42

1,500Hz

Question 43

gray shades on a doppler spetrum are related to

Answer 43

amplitude of the reflected signal number of red blood cells creating the reflection

Question 44

color doppler is pulsed ultrasound technique and is subject to

Answer 44

range resolution or specificity aliasing

Question 45

color doppler is

Answer 45

semi quantitative

Question 46

color doppler reports

Answer 46

average velocities aka mean velocities

Question 47

color doppler gain setting has greatest effect on

Answer 47

jet size

Question 48

doppler packets

Answer 48

multiple pulses are needed to determine RBC celocites by dopplers, single measurement is not enought

Question 49

multiple doppler pulses are call

Answer 49

packet aka ensemble length

Question 50

the packet must balance between accurate velocity measurements and

Answer 50

temporal resolutions, this is why color doppler measures mean velocity

Question 51

disadvanage to doppler packets

Answer 51

more time needed frame rate is reduced temp res is decreased

Question 52

advantages of doppler packets

Answer 52

greater accuracy sensitivity to low flows

Question 53

spectral doppler (pulsed and continuious) measures _______ -______ while color flow measures _____ ______

Answer 53

peak velocity mean velocity

Question 54

color power doppler aka energy mode and color angio advantages

Answer 54

increased sensitivity to low flows not affected by doppler angles unless its 90* no aliasing

Question 55

color power doppler limitations

Answer 55

no velocity measurement slower frame rate and temp res susceptible to motion of trans, patient or soft tissues, called flash artifact

Question 56

spectral analysis

Answer 56

performed to extract or edentify the individual freq making up the complex signal

Question 57

spectral analysis for pulsed or CW doppler

Answer 57

fast fourier transform (FFT)

Question 58

spectral analysis for color flow doppler

Answer 58

autocorrelation or correlation function

Question 59

FFT and autocorrelations are

Answer 59

digital techniques performed by computors

Question 60

autocorrelation is used w color doppler cause of the enormous amount of doppler info that requires processing. It is ____ _____ but ______ than FFT

Answer 60

less accurate faster

Question 61

anremia and doppler

Answer 61

we can always successfully perform a doppler exam regardless of the patients hematocrit

Question 62

RBC closest to the trans will create the highest

Answer 62

amplitude

Question 63

no dppler shift is measured at a _____ angle

Answer 63

90*

Question 64

at what engle will the doppler shift be at max

Answer 64

0*

Question 65

T or F | only pulsed wave dopppler has ample vomules

Answer 65

T

Question 66

T or F | the higher the emitted freq the more likely the pulsed wave signal is to alias

Answer 66

T

Question 67

pulsed wave doppler has a rcv gate that is

Answer 67

adjusted by sonographer

Question 68

nyquist limit -

Answer 68

1/2 PRF

Question 69

errors in imaging

Answer 69

artifacts

Question 70

artifacts are

Answer 70

``` not real missing reflectors iimproper brightness improper shape improper size improper position ```

Question 71

causes of artifacts

Answer 71

violation of assumptions (acoustic artifacts) equipment malfunction or design physics of ultrasound interpreter error (anatomic pitfalls) operator error