Chapter 4: Doppler Imaging Artifacts Flashcards
the study of blood flow through the blood vessels of the body
hemodynamics
difference in fluid energy
energy gradient
No energy gradient =
no flow
the driving force of the blood through the blood vessels
pressure energy
Potential energy converts into _______
kinetic energy
gravitational potentional energy
hydrostatic pressure
describes relationship between gravity, the density of blood, and the distance between an arbitrary reference point (usually the heart)
hydrostatic pressure
form of energy loss; produced when kinetic energy is converted to heat as a result of friction
viscous energy
an object at rest stays at rest, and an object in motion stays in motion unless acted on by an outside first
inertia
total energy in a system never changes; there must be the same total energy at the end of a vessel as at the beginning; types of energy may be different between two points
the law of conservation of energy
kinetic energy + heat energy =
potential energy that was initially found at beginning of vessel
the volume of blood moving through a vessel per unit time
flow
The amount of f low in a blood vessel is ______ proportional to pressure gradient.
directly
systemic circulation
left ventricle of heart
aorta
arteries
arterioles
capillaries
venules
veins
IVC
right atrium of heart
where nutrient and waste exchange occurs
capillaries
vessels responsible for vasoconstriction and vasodilatation in th ebody
arterioles
venous part of systemic circulation
forits capacitance
Approximately ____ of the blood is stored in the veins
2/3
3 layers of vessels
tunica intima
tunica media
tunica adventitia
inner layer of blood vessel
tunica intima
blood vessel layer made of muscle and elastic tissue; arteries have a thicker layer
tunica media
outer layer of blood vessel
tunica adventitia
The _______ supplies the tunica adventitia with its own blood supply.
vasa vasorum
found in large blood vessels at the entrance
plug flow
The velocity profile of plug flow is _____
blunt
results when the red blood cells become chaotic and disorganized, resulting in assortment of velocities
turbulent flow
may occur from high-velocity flow and from tortuous or kinked vessels
turbulent flow
equation used to quantify the degree of turbulence in a blood vessel;
Reynolds number
A Reynolds number greater than ____ = true turbulence
2000
ties together relationship between vessel area, velocity of blood, and volume of blood flow
continuity equation
If an area of a vessel decreases, the velocity must _____
increase
states that an increase in velocity must be accompanied by a corresponding decrease in pressure
Bernoulli’s Principle
The inverse relationship between pressure and velocity is linked to the __________
law of conservation of energy
Any increase in velocity is an increase in energy, and therefore the pressure must ______ to preserve the total energy
decrease
describes the relationship between the volume of blood flow and the resistance to flow in a blood vessel
Pouiselle’s Law
equal to the difference in pressure divided by the resistance to flow in the vessel
flow
If the length of vessel or viscosity of blood increases, there is _______ flow
decreased
If the radius of a vessel increases, the flow _______
increases
If radius doubles, flow increases by a factor of ___
16
loss of energy in the form of heat
friction
flow is equal to the pressure differential divided by resistance
Ohm’s law
hemodynamically significant stenosis, decreased distal flow, leads to significant pressure gradient, cross-sectional area loss of 75%
critical stenosis
A 75% decrease in area corresponds to a __% decrease in diameter
50
resistance of the distal bed of blood vessels
effective resistance
sum of individual resistances when multiple vessels are connected in series
effective resistance
main contributors to the resistance in the cardiovascular system
arterioles
innervated walls can constrict or dilate in response to signals from the brain to either increase or decrease flow distally
arterioles
Is it more detrimental to have more than one stenosis in a vessel or a single substantial lesion in a vessel?
more than one stenosis in a vessel
Higher pressure proximal to a stenosis causes ______ to open up and the blood follows the lower-resistance path
collaterals
Veins located between the capillaries and the right atrium of the heart progressively get _____
larger
Pressure in venules
15 mmHg
Pressure in the right atrium
0-8 mmHg
Hydrostatic pressure at the heart
0 mmHg
Below the heart, the hydrostatic pressure will be _____
positive
folds of endothelial tissue inside of the veins
venous valves
These provide a method to ensure forward flow
venous valves
The difference between the pressure inside the vein and surrounding tissue
transmural pressure
If the patient is supine, the transmural pressure will be ____
low
If the patient is standing, the transmural pressure will ____
high
Vein flow is ____
phasic
variations that relate to respiration
phasic
If there is pulsatility in peripheral veins, this may indicate problems with:
the right side of heart
arteries that feed high resistance bed
triphasic or biphasic flow
arteries that feed low resistance bed
monophasic flow
distal arterioles dilate; increase in diameter of vessels accompanied by pressure drop
proximal stenosis
seen in presence of proximal obstruction; delay in upstroke of systolic component
tardus parvus
When sound impinges on a stationary reflector, the reflected frequency is identical to the transmitted, or incident frequency
Doppler Effect
When a reflector is moving toward the transducer, the reflected frequency will be higher than the transmitted frequency and vice versa
Doppler Effect
difference between transmitted and reflected frequencies
Doppler shift
reflector is moving in a direction that is toward the transducer
positive shift
reflector is moving in a direction that is away from the transducer
negative shift
as frequency increases, intensity of scatter increases proportional to:
fourth power of frequency
The higher the frequency, the ____ scatter, and the _____ attenuation
more
more
As Doppler angle increases, the cosine of the angle _____
decreases
Doppler angle and frequency shift are ______ related
inversely
Most accurate Doppler shift
0 degrees
As angle increases, frequency ______
decreases
There is no Doppler shift at:
90 degrees
determine positive or negative shift; permits bidirectional Doppler
phase quadrature
There is no ____ resolution with CW Doppler
range
compares transmitted and received frequencies
signal processor
transmit time of CW
100%
Duty factor CW
100%
mathematical technique used to break down the signal and produce a spectral waveform
Fast Fourier Transform
derived by tracing the spectral waveform from end diastole to end of next diastole
mean velocity
used to quantitative the resistiveness of the distal vascular bed
Resistive Index
used to determine how pulsatile a vessel is over time
Pulsatility Index
estimate relative difference between systole and diastole
Pulsatility Index
represents how many red blood cells are traveling at that velocity at a specific period of time
envelope
wider range of velocities = ______ envelope
thicker
The area under the envelope is the
spectral window
turbulent flow that demonstrates a filling in of spectral envelope
spectral broadening
transmits pulses of sound and waits for the sound to return in order to determine depth of returning echoes
Pulsed Wave Doppler
Pulsed-Wave Doppler transmits anywhere from __-___ cycles per pulse
5-30
The higher the pulse length, the ____ accurate sampling
more
more accurately calculate the velocities from frequency shifts; shows what flow angle, so velocities can be accurately calculated
angle correction
wraparound of the Doppler signal, where positive shifts are displayed as negative shifts
aliasing
1/2PRF
Nyquist limit
color representation of the Doppler shift information superimposed on grayscale imaging
Color Doppler Imaging
provides information pertaining to both direction and mean velocity
Color Doppler Imaging
processing technique used to obtain color flow information
Autocorrelation
packet size is also known as:
ensemble length
number of pulses per scan line within color gate
ensemble length
The higher the ensemble length = the _____ the sensitivity
higher
Packet size is typically __-__ pulses
10
20
The best frame rate uses the _____ color gate
smallest
BART
blue away red towards
Three main components of Color Doppler Imaging:
hue
saturation
brightness
the color itself determined by its wavelength
hue
how much white is added compared to original color
saturation
how intense the color is; related to amplitude of the signal
brightness
wraparound of the color scale
aliasing
Aliasing is eliminated by:
increasing the PRF/scale
threshold for displaying color pixels instead of grayscale pixels
color priority
smallest component of a 2D image
pixel
flowing blood = ____ amplitude, ____ velocity signal
low
low
uses low pass filter to eliminate the signal from the blood and only show color information representing wall motion
Tissue Doppler imaging
frequency shift on which flow information is based is equal to 0 at that critical angle
Power Doppler
ignores frequency shift and only focuses on the amplitude of the shift
Power Doppler
inadvertent motion interrupts quality of signal
flash artifact
used for measuring myocardial function
cardiac strain and strain rate
changing of the shape of the muscle as it lengthens and contracts
strain
permit evaluation of the deformation of the cardiac wall to evaluate for ventricular function
cardiac strain and strain rate
method used to obtain strain information
speckle tracking
