MEDS12001 Lecture Notes - Lecture 8: Medical Ultrasound, Hemodynamics, Flow Velocity

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25 May 2018
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2 | P a g e
WHAT IS POWER DOPPLER?
Displays the density of moving blood (the
greater the density the increased the
amplitude)
o Each Doppler shift frequency is given a
shade of the hue of orange, which also
has amplitude.
o Can we display this amplitude?
o
o No red/blue but good at detecting
small areas of flow and low flow
CPA = colour power angio
Does not demonstrate any flow velocity
or directional information
More sensitive than colour Doppler for
flow detection
No aliasing associated with Power
Doppler
Not angle dependent perpendicular
scanning is possible
A variety of colour Power maps are
available
No haemodynamic changes or flow
characteristics able to be demonstrated
Useful for tissue or organ perfusion
Useful for assessing vascularity of
tumours
Useful for assessing trickle flow
Helpful in wall ulceration definition
Can be used in conjunction with Colour
Doppler to increase diagnostic value
Specifications:
1. No velocity or direction information
2. No aliasing only amplitude not Doppler
shift display
3. Angle independent
Power Doppler can detect flow, even
perpendicularly to the flow direction. The
transducers can proved essentially false angles,
which can have small Doppler shift amplitudes
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3 | P a g e
Variety of colour maps are available
Advantages
1. More sensitive than colour Doppler for
flow detection
THEREFORE: slower flow detection and
deeper penetration
2. Less angle dependent
THEREFORE: perpendicular scanning is
possible
3. No aliasing
THEREFORE: outline of vessel/organ see
well
completely perpendicular
Disadvantages
1. No flow direction information
THEREFORE: no antegrade or retrograde
determination
2. No velocity or speed information
THEREFORE:
Velocity changes, aliasing not assessed
with power Doppler
3. No flow characteristics information
Haemodynamic changes not assessed
i.e. Laminar vs Turbulence, no aliasing etc.
Applications
1. Tissue or organ perfusion. E.g. Kidney,
liver, spleen, testicles, ovaries, transplants
2. Vascularity in tumours
3. Transcranial dopppler
4. Trickle flow very slow flow in high grade
stenosis
5. Arterial stenosis good for wall, ulcer
definition
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Document Summary

Specifications: no velocity or direction information, no aliasing only amplitude not doppler shift display, angle independent. Cpa = colour power angio: does not demonstrate any flow velocity. Power doppler can detect flow, even or directional information perpendicularly to the flow direction. The: more sensitive than colour doppler for transducers can proved essentially false angles, flow detection, no aliasing associated with power which can have small doppler shift amplitudes. 2 | p a g e: variety of colour maps are available. Therefore: no antegrade or retrograde determination: no velocity or speed information. Therefore: more sensitive than colour doppler for. Velocity changes, aliasing not assessed flow detection with power doppler. Therefore: slower flow detection and: no flow characteristics information deeper penetration, less angle dependent. Haemodynamic changes not assessed i. e. laminar vs turbulence, no aliasing etc. Applications possible: no aliasing, tissue or organ perfusion.

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