Spectral Doppler Displays

Question 1

spectral doppler aka

Answer 1

pulsed wave

Question 2

how many scan lines in spectral doppler

Answer 2

firing along a single scan line (versus colour doppler which fires 3-32 pulses per scan line, 10-20)

Question 3

how many cycles per pulse in doppler

Answer 3

5-30 cycles per pulse

Question 4

pulsed wave doppler systems provide the ability to ___

Answer 4

select depth from which doppler info is received (CW cannot do this)

Question 5

range gating

Answer 5

ability to select info from a specific depth along beam

Question 6

what does range gating enable (2)

Answer 6

depth sensitivity and a small sample volume

Question 7

sample volume

Answer 7

specific area being assessed “gate”

Question 8

what is an effective sample length? sample width?

Answer 8

sample length = 1/2 SPL + gate length

sample width = beam width

Question 9

spectral doppler detects (4) of blood flow

Answer 9

same as colour :
presence
speed
character 
direction

Question 10

spectral doppler allows for quantification of blood flow- true or false

Answer 10

true

Question 11

what is on the x and y axis of spectral doppler

Answer 11

x - time

y - doppler shift or velocity

Question 12

bidirectional doppler what and where

Answer 12

detects positive and negative shifts IN THE doppler-shift detector/ quadrature phase detector

Question 13

what is fast fourier transform and WHERE

Answer 13

within spectrum analyzer
Determines frequency spectrum
Determines each doppler shift frequency (x) and its strength (y)
converts voltage over time to amplitude over frequency

Question 14

each point of a spectral waveform shows (3)

Answer 14

direction (+/-)
magnitude (how fast)
amplitude (brightness)

Question 15

what factors affect direction? (2)

Answer 15

coming away/towards transducer

direction of steering

Question 16

what factors affect magnitude? (2)

Answer 16

speed of blood flow (e.g. within stenosis)
doppler angle (larger angle, smaller cosine, smaller Doppler shift, larger calculated velocity)

Without angle correct, it is a slower calculated velocity -therefore UNDERESTIMATES velocity with a 0 angle

Question 17

what factors affect amplitude? (3)

Answer 17

intensity of returning echo

• concentration of RBCs
• reflectors
• impedences

Question 18

gate size/sample volume affects

Answer 18

range resolution

Question 19

what is the opposite of range resolution

Answer 19

range ambuiguity

Question 20

gain

Answer 20

amplification of incoming echoes voltages

Question 21

invert

Answer 21

arteries + above BL,

veins - below BL

Question 22

if you want more positive signals, do what?

Answer 22

move baseline down

Question 23

wall filter

Answer 23

gets rid of clutter, cuts off slower/low frequency flows

Question 24

what affects the scale?

Answer 24

PRF

Question 25

increase PRF and what happens to the scale

Answer 25

increases

Question 26

if you decrease PRF too much what happens

Answer 26

aliasing

Question 27

what happens if you increase PRF too much?

Answer 27

shows faster flow speeds but can produce a poor signal because of wasted space

Question 28

if you don't correct the angle, will the speed be underestimated or or over estimated?

Answer 28

underestimated because increasing the angle: increases the speed decreases doppler shift

Question 29

true/false - arteries are phasic and lower velocity wave form

Answer 29

FALSE thats veins | arteries are pulsatile and higher velocity waveform

Question 30

high resistance flow seen in

Answer 30

external carotid artery | extremities

Question 31

low resistance flow seen in

Answer 31

internal carotid artery, common carotid artery, blood hungry organs

Question 32

factors that characterize a stenosis (4)

Answer 32

1. decreased area increased velocity 2. turbulence (if surpassed reynolds number) 3. potential for aliasing 4. spectral broadening

Question 33

what is spectral broadening

Answer 33

caused by turbulent flow where theres a greater variation in the velocities, causing vertical thickening of the spectral trace narrowing of window

Question 34

spectral broadening can be produced artificially (3)

Answer 34

increased gain increased sample size beam spreading with wide aperture arrays

Question 35

what waveforms suggest a proximal stenosis (2)

Answer 35

upstream, pre-stenosis tardus parvus waveform monophasic waveform

Question 36

tardus parvus waveform

Answer 36

pre-stenosis waveform that is very slow and rounded

Question 37

what may suggest a distal stenosis?

Answer 37

increased resistance

Question 38

if the ICA waveform (recall low resistance) looks like the ECA wavefirm (recall high resistance) what can this suggest?

Answer 38

distal stenosis

Question 39

quantitative index

Answer 39

acceleration time

Question 40

what does quantatative index show

Answer 40

tardus parvus

Question 41

spectral limitations (5)

Answer 41

1. sonographer skill 2. body type 3. aliasing 4. movement 5. range gated to specific depth

Question 42

how can you fix aliasing (4)

Answer 42

1. adjust baseline 2. lower operational frequency 3. increase doppler angle 4. increase PRF

Question 43

spectral doppler is continuous wave and pulsed wave

Answer 43

true

Question 44

what is the sample volume like in CW

Answer 44

LARGE overlapping sample volume (due to two transducer elements)

Question 45

what is the limitation to CW

Answer 45

range ambiguity (poor range resolution) PW has great range resolution

Question 46

benefit to CW

Answer 46

CW cannot alias because there's no PRF in CW | can pickup very high max values without aliasing

Question 47

what type of doppler shows perfusion?

Answer 47

power

Question 48

what type of doppler shows quantitative?

Answer 48

spectral

Question 49

what type of doppler shows global

Answer 49

doppler shift and doppler power

Question 50

Without angle correct, will calculated velocity be higher or lower?

Answer 50

Lower ``` Cos0 = 1 Cos60 = 0.5 ``` Increasing the angle puts a fraction in the denominator of the velocity equation, increasing the calculated value