Chapter principles Notes
Doppler Shift formula
FD = (2 * Vcos0 * f0)/c
flow and conform
the resistance to flow
What is the unit for viscosity
poise = .1 kg/m-s
How much higher is the viscosity of blood plasma compared to water?
The study of blood flow through the vessels and the changes its force stimulates
liquid with solid componenets
supplier of nutrients
viscosity of water
viscosity of plasma
viscosity of blood
viscosity of blood range
.02 - 10 poise
What is needed for blood to flow
high pressure on one end and low pressure on the other end - path of least resistance
What happens if there is equal pressures applied to both ends of a liquid filled tube?
What can generate pressure differences?
ions crossing a permeable membrane
the driving force needed for flow of blood
What does a constant driving pressure produce?
Define Volumetric flow rate
volume of blood passing a point per unit of time
Volumetric flow rate formula
Flow rate = V/t
If flow resistance increases what happens to volume flow rate?
If pressure difference increases what happens to volume flow rate?
5000 mL/min 5 liters
5 liters circulates all around in 1 min
In a static fluid the pressure is ________
pressure is equal
The flow resistance in a long straight tube depends on what?
* tube length (L)
* radius (r)
What happens to resistance when length is increased?
What happens to resistance when radius is doubled?
decreases by a factor of 4
What happens to resistance when viscosity is increased?
flow = pressure*diameter/ strength*viscosity
steady flow in a long straight tube
What happens to flow rate when length is increased?
What happens to flow rate when diameter is increased?
What happens to flow rate when viscosity is increased?
What happens to flow rate when pressure difference is increased?
define Hydrostatic pressure
Weight of blood pressing against vessles of heart to level of measurement.
How is the circulatory pressure measured
patient in supine position, weight of blood is eliminated.
What is the average circulatory pressure?
Formula for pressure above the heart
circulatory pressure - hydrostatic pressure
above = CP - HP
Formula for pressure below the heart
circulatory pressure + hydrostatic pressure
below = CP + HP
What is the hydrostatic pressure of the fingers?
What is the pressure at the fingers?
120 - 50 = 70 mHg
What is the hydrostatic pressure of the head?
What is the pressure at the head?
120 - 30 = 90 mHg
What is the hydrostatic pressure of the heart?
What is the pressure at the heart?
120 - 0 = 120 mHg
What is the hydrostatic pressure of the knee?
What is the pressure at the knee?
120 + 75 = 195 mHg
What is the hydrostatic pressure of the ankle?
What is the pressure at the ankle?
120 + 100 = 220 mHg
During inspiration what happens to the venous flow in the legs?
diaphragm moves down
During inspiration what happens to the venous flow to the heart?
diaphragm moves down
During expiration what happens to the venous flow in the legs?
diaphragm moves up
During expiration what happens to the venous flow to the heart?
diaphragm moves up
What are the types of flow?
What is plug flow?
at the entrance of, the speed of the fluid is essentially constant across the tube
blood moves as a unit
What is laminar flow?
all flow is in same direction
maximum at center and 0 at tube walls
what is Parabolic flow?
type of laminar flow
center speed is 2x the average speed of other stream lines.
What is Disturbed flow?
Type of laminar flow
when the parallel stream lines is altered due to plaque or bifurcation.
random chaotic, occurs at a stenosis
Bruits can be heard
What is Bruits?
A sound heard when there is turbulent flow in an artery.
What is Eddies flow?
the net blood flow is in a direction of flow but some blood is heading backwards.
What is the Reynold's number?
A Unitless number - predictor of turbulence
when reynold's number is 2000 - 2500 turbulence is likely
formula for Reynolds #
R# = (average flow speed * diameter * density) / viscosity
If diameter increases what happens to the Reynolds #?
If flow speed increases what happens to the Reynolds #?
If density increases what happens to the Reynolds #?
If viscosity increases what happens to the Reynolds #?
Viscosity is the only increased variable that decreases Reynolds number
Being directly influenced by the effects of the beating heart with pulsatile variations of increasing and decreasing pressure and flow speed.
What does pulsatile flow rate depend on?
stretch and squeeze
in the aorta, the aorta valves close preventing backward flow.
The aorta stretches
pushing blood forward
after forward flow,
decrease of pressure and contraction of vesels causes reverse flow
just a little
Explain phasic Flow
venous flow is phasic using valves to prevent flow reversal
If the vessel is nice :) what happens to flow speed?
attempt to maintain continuity throughout vessel
If an area of constriction occurs the flow attempts to keep the same volume
Speed is increased!
Due continuity rule, What happens to flow speed if the diameter is halved?
Speed is increased x 4
Due continuity rule, What happens to flow speed if the diameter is halved and the flow is parabolic?
Speed is increased x 8
Increase in velocity is accompanied by a corresponding decrease in pressure
it is this decrease in pressure that causes lift
Explain what happens with speed with bernoulli's Principle
Explain what happens with pressure with bernoulli's Principle
Explain what happens with volume with Bernoulli's Principle
Change in frequency of sound as a result of motion between source and receiver
Factors that influence Doppler
Motion of source
Motion of the reflector
Motion of receiver
Doppler Shift equals
Reflected Frequency - incident frequency
RF - IF
Incident Frequency AKA
If receiver and transmitted are stationary, explain the Doppler shift.
NO Doppler shift
Doppler Shift moving toward you.
compression of cycles in front of source
receiver hears more cycles per second
Is the Doppler shift coming toward you, positive or negative?
receiver frequency is greater
Doppler Shift moving away from you.
spreading of cycles behind the source
receiver hears less cycles per second
Is the Doppler shift going away from you, positive or negative?
receiver is lower
What are the factors that influence Doppler?
Motion of source
motion of the reflector
motion of receiver
Explain Doppler for DMS.
The source & receiver are the same
only variable is a moving reflector
What is Doppler SHift?
series of pulses are fired at a moving RBC
The echoes from a moving RBC will sow difference in the frequencies that returns to the transducer.
What is the Doppler Shift equation?
FD = (V * f0)/c
What was the error in the original Doppler equation?
Since there were two shifts it did not work a 2* was added to the equation
FD = (2 * V * f0)/c
What else causes an error in the Doppler SHift equation?
What is the correct Doppler Shift equation?
FD = (2 * V* cos0 * f0)/c
What happens to the Doppler shift when the beam is perpendicular to the direction of blood flow?
Cos 90 = 0
No Doppler shift
What happens to the Doppler shift when the beam is parallel to the direction of blood flow?
Cos 0 = 1
Maximum Doppler shift
At what angle is the maximum Doppler shift?
90° and 180°
If the angle increases what happens to the cosine?
If the angle increases what happens to the Doppler shift?
If the angle increases what happens to the flow?
If the cosine increases what happens to the Doppler shift?
What angle does your beam need to be at when you drop your gate into the vessel?
Between -30° and 60°
Why is echo able to to obtain correct Doppler shift outside of 30° and 60°?
The wall angle is big enough to rid reflection
Why can't the Doppler shift be estimated below -30°?
pulse is lost to reflection
Why can't the Doppler shift be estimated above 60°?
too much error
The cosine changes rapidly at large angles
What is demodulation in Doppler?
Process of extracting Doppler shift frequency from the transducer frequency
If the return echo is 5,010,000 with a 5 Mhz transducer, what is the Doppler frequency?
How do you angle correct for Doppler?
Your orientation line must be parallel to the vessel
What are the different types of Doppler?
How many pulses in B-mode to write 1 line?
How many pulses in color flow Doppler to write 1 line?
5 - 30
10 - 20 average
Describe the process of color flow Doppler
1. the frame for greyscale is built
2. the frame for color Doppler is built
Why is temporal resolution important for Doppler?
Frames need to be built as fast as possible
What is color mapping?
the brightness of the dots can be represented by colors other than white/grey
easier on the eyes
What is the Doppler shift frequency proportional too?
the number of red blood cells
always enough RBCs even when the patient is anemic
spectrum is the entire range of Doppler shift frequencies created
Of the many velocities in a vessel spectral collects them all.
Limitations of Color Doppler?
- only shows statistical representation of the entire spectrum
- only demonstrates mean velocities
- angle dependence
- slow frame rates (temporal res takes hit)
- autocorrelation - fast but not fast enouh to demonstrate entire spectrum
What are the 3 components of color?
What determines hue?
What color will equal percentages of each color create?
What determines saturation?
determined by how much white is added
white is a mixture of all colors
is a complete white screen saturated?
What is luminosity?
the brightness of saturation & hue
how intense a color is related to the amplitude of signal
What does changes in hue, saturation or luminance indicate?
increase in Doppler shift magnitude
What is a variance scale?
shows a change in hue from left to right
Sign of the cross
velocity - variance
What is autocorrelation?
preforms demodulation and determines -+ sign
determines the mean velocity
determines the variance
stores that info in the memory
assigns color to pixel with a change in frequency due to motion
how many pulses are required for a 1 speed estimate ensemble?
3 pulse minimum
more for improved accuracy
a mathematical process that yields Doppler shift information in color Doppler instruments
What is the ensemble length?
the number of pulses used for each color scan line
5 - 30
10 - 20 average
What is another name for ensemble?
What determines depth?
echo arrival time
What determines brightness?
echo intensity or amplitude
What does a different returning echo indicate?
a measure of data that is spread around the mean
small variance vs. large variance
small differences are measured well
mean values do not represent large differences very well.
How do you turn on gate location?
turn on spectral
True or False?
A large gate is better than a small gate.
How do you move gate? size?
select again changes size
Color flow gain
almost the same as over all gain
increases the amplitude to all colors on screen
what do the colors mean on the color map?
flow toward - red
highest Doppler shift - yellow
flow away - blue
highest negative Doppler shift - teal
what is another name for color scale?
How do you adjust color scale?
What do the filters do?
allows for elimination of clutter from tissue motion
wall filters - wall thumptilters
Why would you adjust wall filters?
calm down mess
176 slide 1 & 2
what is the significance of large ensemble length?
more sensitivity - ability to detect low flow
decreased temporal resolution
color averaging 5 or 6 frames then averages
improves sensitivity - ability to detect low flow
What is the priority to be assigned color pixels?
What happens when Doppler shift is set to low priority?
Grayscale is priority
color flow doppler threshold
setting the priority
velocity mode- color map
What is the disadvantage to Color flow Doppler
Temporal resolution takes a hit.
What can you do to make the temporal resolution the best when using color flow Doppler?
make the gate as small as possible
What does gain do when using Color Flow Doppler?
increase the amplitude to all colors on a screen
What can you do to reduce the aliasing with color flow Doppler?
Color Flow Doppler
What is the purpose for using filters?
allows elimination of clutter from tissue motion
What does this?
Exclude Doppler signals with low frequency, and high amplitude from moving tissue, such as a vessel wall.
High pass - Wall filters
AKA Wall thump filters
What can you do in color flow doppler to ensure entire waveform is seen.
adjust the baseline
What is ensemble length
# of pulses/scan line
What happens with a high ensemble length?
more lines = more accuracy
*the ability to detect low flow
What happens to temporal resolution when ensemble length is increased
temporal is reduced
Color flow doppler
What is smoothing?
5 or 6 frame averaging
What is another name for smoothing?
Explain color priority.
machine set priorities for processing
Doppler shift tends to main priority
you can set Doppler to low priority which will make grayscale high priority
In a steered box find the home and follow color map
What does power doppler measure?
List other names for Power Doppler
Color Power Doppler
color doppler energy
color power angio
look for keywords angio and energy and
What are the advantages of Power Doppler?
greater sensitivity to low flow
no worry of angles
What are the disadvantages of Power Doppler?
No information of velocity or direction
What are the benefits to pulsed wave Doppler
measure peak velocities
select location (place gate)
adjust sample size
has range resolution
What is DF for CW wave Doppler?
100% or 1
With CW Doppler what determines the operating frequency?
Disadvantages of CW Doppler
CW Doppler has no damping - narrow bandwidth
What does large sample volume in CW Doppler cause?
What is the Fast fourier transfomation
mathmatical formula for drawing waveforms
several velocities - several shifts
copulates all and then plots doppler shifts as velocities
How do we adjust x axis?
changing sweep speed
What is sweep speed?
# of cycles
What kind of shift frequency does plug flow have?
single shift - up stroke
as rises band thins
as falls band thickens
What do brighter dots on the waveform mean?
more red blood cells
minus sign on Doppler shift means
negative doppler shift
The area under the envelope is called what?
Turbulence will cause the spectral envelope to?
what causes spectral broadening?
gate too close to the edge
too large a gate (sample)
What is the relationship between Doppler shift and frequency?
How can you get rid of aliasing?
Systolic Diastolic Ratio
Systolic Diastolic Ratio
hump with side
True or False
normal triphasic flow can happen during exercise.
What is triplex imaging
what is Duplex imaging
to fast for system
Name the filters
wall thump filter
high pass filter
what do filters do
get rid of clutter caused by low amp signals
changing the scale changes the ____
PRF is determined by
sampling rate should be what to avoid aliasing
same as spectral gain
brightness of dot amplitude
broadening clears out with lower gain
what angle should be used?
less than 60 degrees
Which type of Doppler uses a gate?