week 2- Doppler Blood flow Flashcards
Degree of pulse wave dampening
pulsatility
๐ทulsatility Index equation
PI=(๐บโ๐ซ)/๐ด
- peak systolic
- minimum diastolic
- mean velocity
Pulsatility index is ___ of the angle
independent
flow that is dampened by ___ disease will have a LOWER PI
proximal
low PI indicated
disease proximal to the transducer
after exercise high pulsatility extremity arteries become ____ pulsatility
low
Resistive index equation
๐น๐ฐ =(๐ท๐บ๐ฝโ๐ฌ๐ซ๐ฝ)/๐ท๐บ๐ฝ
- peak systolic velocity
- end diastolic velocity
Measure of pulsatile blood flow that reflects the resistance to blood flow caused by microvascular bed distal to the site of measurement.
resistive index
resistance index of 0 means
continuous flow
resistance index of 1
systolic flow, no diastolic
resistance index of -1
reversed diastolic flow
RI is an indicator of ____ resistance
peripheral
Higher resistance flow if there is disease ___ to the probe
distal
if resistance index is between 0 and 1 it means there is ___ flow towards the organ
constant
an organ where you would find constant flow
brain, placenta, CCA, vertebral
the following are indicators of ___ flow:
- Central velocities are greater than peripheral velocities in a vessel
- Uniform velocity
- Clear spectral window
laminar flow
the following are indicators of ___ flow:
- Non uniform and disorganized blood flow
- Spectral broadening โ filling of the spectral window proportionate to severity of flow disturbance
- Indicative of pathology but can occur normally
turbulent
The following is seen with ___ resistance flow:
Broad systolic peaks
Forward flow through diastole
Monophasic
low
The following is seen with ____ resistance flow:
PS is tall and sharp in diastole
Forward flow is always present throughout diastole
moderate
low pulsatility is associated with ___ resistance flow
low
ECA, SMA during fasting present with ___ flow
moderate resistance
what waveforms will NEVER cross the baseline
low, moderate
t/f: low flow is always above base line
FALSE - can be below depending if the scale is inverted
the following is seen with ___ resistance flow:
Tall, narrow and sharp systolic peaks
Reversed or absent ED flow
Triphasic waveform
high
high pulsatility is seen in ____ arteries and indicates ___ resistance flow
- extremity
- high
3 phases in triphasic waveform
- sharp systolic
- brief reversal flow
- brief forward flow
What superimposes a blood flow image on a standard grey scale image
colour doppler
Veins have a ___ PRF (gains), why?
lower
-to detect low velocities
arteries have a ___scale, why?
higher
-limit aliasing
increasing the scale ____ the aliasing
decreases
doppler angle
45-60 degrees
why is doppler angle important
tell what way blood is flowing
colour box width decreases the ___
frame rate
too much colour gain can cause ____
bleeding
-misrepresentation of colour flow outside vessel, making pathology
increasing gain increases the ___ of the signal
amplitude
This technique eliminates artifacts caused by heart and vascular pulsation
wall filter
wall filter reduces ___ frequency noise
low
what is the risk of setting the wall filter too high
difficulty detecting slow flow
changes the colour velocity range
baseline
changes what colour represents flow towards the transducer
invert
what does a colour map show
the doppler signal
increasing luminance of red and blue indicate increasing ___ and ___ doppler shifts respectively
- positive
- negative
the minimum number of samples required to avoid aliasing; doppler shift freq above which aliasing occurs
nyquist limit
a misrepresentation of the Doppler shift in a negative direction occurring when the pulse repetition frequency is set too low
alaising
colour doppler is/ is not angle dependent?
IS
advantages of doppler
- Demonstrates blood flow
- Determines direction of flow
- Demonstrates non-vascular motion (ureteral jets)
- Asses flow in the entire lumen โ not just within the doppler gate
- Can help differentiate between occlusion and severe stenosis
True flow reversal involves ___ regions between the opposite colours
dark
what is a stenosis
narrowed portion of arterial lumen
there is a ____ velocity through the stenotic zone to maintain flow volume
increased
what are the 3 important velocity measurements
Peak systolic volume
End diastolic volume
PSV ratio
what is the first parameter to increase as the lumen narrows
PSV
<50% stenosis generally EDV is
unaffected
moderate stenosis (50-70%) EDV ___
increases proportionally to degree of stenosis
severe stenosis (>70%) EDV ____
can be very high
allows for patient to patient hemodynamic variables (PT is their own physiologic standard)
PSV ratio
Maximum ____ occurs within the 1st cm beyond the stenosis, minimizes by 2cm and normalizes by 3cm
turbulence
spectral broadening and flow reversal is indicative of
turbulence
increased RI would be shown ___ from the stenosis
distal (down the road)
Pulsatile index tells you what happened ____ measurement
proximal (before)
what is Tardus Parvus
pattern of doppler waveform resulting from arterial stenosis
In Tardus Parvus, it takes ____ (more/less) time to reach peak velocity
more
in tardus parvus, flow velocity is ____
low
Decreased peripheral resistance allows blood to flow through diastole in ____
tardus parvus
