Doppler Flashcards
What does doppler focus on?
hemodynamics and physiology
___ Doppler, Austrian physicist, described the Doppler effect in the year ___
Christian, 1842
Describe the doppler effect
f increases as sound source moves closer
f decreases as sound source moves away
Doppler shift is the difference between
transmitted frequency and received frequency
positive doppler shift
rf > tf
negative doppler shift
rf < tf
is Doppler shift within the audible range?
yes
how is Doppler shift related to speed
direct
measured velocity = ___ x cosine
true velocity
in the doppler equation, v stands for
velocity of blood flow
in the doppler equation, cos stands for
angle of blood flow and US beam
in the doppler equation, change in frequency stands for
Doppler shift (can be pos. or neg.)
in the doppler equation, 2 stands for
double Doppler shift (reception and reflection)
in the doppler equation, fo stands for
known transmitted frequency
in the doppler equation, C stands for
speed of sound in soft tissue
how is change in frequency or Doppler shift related to reflector
direct
two types of doppler
CW
PW
simultaneous 2D imaging and Doppler
duplex imaging
how many crystals in CW doppler
2
one is always transmitting
one is always receiving
benefit of CW
accurate measurement of high velocity
cons of CW
poor range resolution
range ambiguity
what is range resolution?
being able to select the exact location where velocities are measured
what is a PEDOF probe
non imaging CW transducer
high signal to noise ratio, increased sensitivity
small footprint
easy to angulate
how many crystals in a PW doppler
1 crystal
alternates transmission and reception
what does the PRF determine
frequency shift
maximum frequency shift
1/2 PRF
Nyquist limit = ?
1/2 PRF
what happens when the Doppler shift is greater than the nyquist limit?
aliasing
what is aliasing
false display of velocity (wraps around image)
relationship between depth and PRF
inverse
3 factors determining aliasing
increased depth
low PRF
high velocity
how to resolve aliasing
use CW
shallower depth
lower f transducer
shift baseline
has multiple sample volumes or gates along scan line
color PW
sample volume is measured in max or mean velocity?
mean
BART system
blue away
red towards
we use color doppler to
visualize anatomic and hemodynamic info at the same time
what is an autocorrelator
compares frequency shift on a scan line to the other gates on the scan line
color is assigned where the f shift exists
what does color doppler display include?
blood flow direction and velocity
frequency aliasing
laminar and turbulent flow
timing of color doppler signals
what does frame rate mean
frames per second
frame rate depends on
depth of sector
sector width
density of scan lines
number of gates along each scan line
how does high frame rate affect sensitivity?
high frame rate = good sensitivity
what can we change on the frame rate of color doppler
depth of sector
sector width
how can we increase the frame rate / sensitivity in color doppler
narrow sector / increase PRF / shallower depth
can color doppler alias?
yes, it is PW
graphic display of blood flow velocities over time
spectral doppler
FFT processor stands for?
what does it analyze?
fast Fourier transform
frequency shift
y axis of spectral doppler
velocity and direction of blood flow
x axis of spectral doppler
time
positive shift in doppler is
above baseline
negative Doppler shift appears
below baseline
t or f: color of doppler represents average f shifts in the area
true
do blood cells move at equal velocities in doppler?
no, they each create different doppler shifts
how is intensity/brightness related to # of RBC moving at that velocity at that time
direct
streamline flow
laminar
turbulent flow
flow is irregular
which has range resolution?
CW or PW?
PW
does CW have range resolution or range ambiguity?
range ambiguity
Doppler Controls:
Reject =
reduces # of shades of grey to help with envelope detection
Doppler Controls:
compression / dynamic range =
reduces # of shades of gray
Color of TR in apical 4?
blue, away from trx
Color doppler:
White means?
Black means?
high f shift
no f shift
audible range (doppler range)
20 Hz - 20 KHz
cosine of 90 =
0
strive to be parallel to flow or angle less than __ degrees
20
spectral doppler provides?
direction velocity
duration
timing / point in cardiac cycle
acceleration time
period before spike in m mode (onset of flow to peak)
deceleration time
peak of curve in m mode (peak to end of flow)
what views do we use to find LVOT / AV velocity
apical 3 or 5
LVOT is always less than AV
shape of LVOT blood flow tracing
V shape
LVOT blood flow time
.7 - 1.1 m/s
AV blood flow time
.2 - .4 m/s higher than LVOT due to lower CSA at leaflet tips
it is common practice to evaluate the AV velocity with CW or PW?
CW
normal peak velocity of AV
1 m/s
normal AVA (aortic valve area)
3 - 4 cm2
velocity > 4 = severe aortic stenosis
AVA > 2 cm squared
AVA < .7 cm sq = severe stenosis
what view do we get the best RVOT and PA velocity
short axis or sometimes long axis
max velocity of RVOT / PA
1 m/s
what window do we get LV inflow in
apical 4 at leaflet tips
normal E velocity
1 m/s
normal A velocity
2-4 cm/s
E/A ratio should be greater than or less than 1
greater than 1
RV inflow velocity
.3 - .7 m/s
PW sample should be positioned at
leaflet tips
TR provides monographers with ability to calculate __
pulmonary artery pressures
Is TR normal?
yes, 70 to 80% of people have a small amount
how does blood flow into the LA
via 4 pulmonary veins
RU, LU, RL, LL
PV that is most widely used
RUPV
view we want for Pulmonary vein flow
apical 4
PW or CW for pulmonary vein flow
PW, has pulse range resolution
where do we place the sample volume for pulmonary vein
1-2 cm into pv
PV flow has 3 distinct waveforms…
systolic antegrade flow
diastolic antegrade flow
atrial retrograde flow
S wave
systolic forward flow as a result of LA relaxation and movement of MV annulus toward apex with ventricular systole
same positioning as E wave
D wave
diastolic forward flow during diastole
occurs when there is an open conduit between PV, LA,
open MV and LV
usually lower velocity than S wave
AR wave
atrial flow reversal
retrograde flow into PV after atrial contraction
normal velocities are low
Severe MR may cause blunted __ wave (retrograde flow)
S
pulmonary vein characteristics are a good way to determine ___
diastolic dysfunction
view for hepatic vein
subcostal long axis view of IVC
hepatic vein flows into
RA
hepatic flow is the same as ___ flow
IVC flow
is spectral doppler of hepatic flow more accurate than IVC?
yes, velocities increase with respirations in IVC
Hepatic vein waveforms
S - systolic forward flow
D - diastolic forward flow
AR - retrograde flow
what happens with respiratory variation and flow
inspiration increases antegrade flow
expiration increases retrograde flow
TR
75% functional - normal
24% structural - something wrong with valve
we can calculate TR pressures using ___
pulmonary pressures
normal velocity of TR
less than 2 m/s
what does the PRF in PW equal?
sampling rate
which doppler type has range resolution
PW
LV inflow velocity
2-4 cm/s
rv inflow seen in what view
apical or RV inflow view
