• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/57

Click to flip

57 Cards in this Set

  • Front
  • Back
What is volume flow rate?
Volume flow rate is the volume of flow passing through a vessel or location per unit time.
VFR formula/Pousille's equation
Q= Delta P x Pie x Radius cubed/8nl
What are the 4 factors that affect volume flow rate?
The 4 factors affecting volume flow rate are:
Pressure difference, tube diameter, tube length, viscosity
Define the relationship of VFR with resistance.
VFR and resistance have an inverse relationship. If resistence goes up then VFR will go down.
Resistence formula
Resistance ...
8nl/pie x radius cubed
What is the most important component that affects the VFR in Poiseuille's equation?
The most important component affecting VFR in poiseuille's equation is vessel size (diameter/radius). This is because it is cubed so any change in diameter/radius will have a big effect.
What is plug flow?
Plug flow is flow at the vessel origin or enterance. The viscosity is constant across the width of the vessel.
What is laminar/parabolic flow?
Laminar/parabolic flow is stead flow. Flow is fastest in the center due to low resistence and slower near the walls due to friction from the walls (higher resistence). Flow is in straight and parallel lines running in layers. Laminar flow is used for velocity check (sample)
What is disturbed flow?
Disturbed flow is when parallel streamline flow is altered or "disturbed" from their straight form. In natural setting it is seen at bif and in pathology it is seen pre-stenosis.
What is turbulent flow?
Turbuelent flow is random and chaotic flow. Speed AND direction are chaotic. Flow creates circles/swirling patterns known as Eddie currents. Turbulent flow is seen post-stenosis.
What is reynolds number?
Reynolds number predicts the onset of turbulence. If reynolds number exceeds 2000 turbulence occurs.
** 1800 - 2000 = disturbed flow
Reynolds number formula
reynolds number formula
Velocity x density x diameter/viscosit
Define continuity rule.
According to continuity rule, volume flow must be CONSTANT pre- at and post- stenosis. Blood is neither created nor destroyed as it flows through stenosis.
Define Bernoulli's effect.
Bernoulli's effect ... There is a drop in pressure at stenosis associated with increased flow speed. This decreased pressure in regions of high flow speed is known as bernoulli's effect.
What happens to pressure and velocity at stenosis?
At stenosis, pressure decreases and velocity increases in order to maintain continuity rule.
If the pressure gradient increases, flow _____
If the pressure gradient increases, flow INCREASES
If the resistence increases, VFR ________
If the resistence increases, VFR DECREASES
List the variables on which flow resistence depends upon.
Flow resistence depends on...
Length (increasing) Viscosity (increasing) Diameter (decreasing) all resulting in INCREASED resistence
Flow resistence decreases with an _____ in vessel radius.
Flow resistence decreases with an INCREASE in vessel radius
What happens to energy at stenosis?
At stenosis, pressure energy is converted into kinetic energy.
List the variables increase which decrease VFR (those with inverse relationship)
Viscosity increased and/or length increased results in a decrease in VFR
What happens to the speed of flow at stenosis?
At stenosis velocity INCREASES, the flow speeds up
At stenosis the pressure is _____ than the proximal and distal locations
At stenosis the pressure is LOWER than the proximal and distal locations
What happens to the VFR at Stenosis?
At stenosis VFR stays CONSTANT (continuity rule)
Define velocity.
Velocity is the speed and direction of flow.
Define doppler effect.
Doppler effect is a change in received frequency as a result of relative motion (motion can be with the receptor, reflector or sound source)
Define doppler shift.
Doppler shift is the difference between emitted frequency and received frequency.
When the received frequency is smaller than the initial frequency, what kind of doppler shift happend?
In doppler shift, if the received frequency is smaller than the initial frequency, the result is NEGATIVE doppler shift. Flow is going AWAY from the Tx.
Define positive doppler shift.
Positive doppler shift is when the received frequency is greater than the initial frequency (flow is coming TOWARDS the Tx
Smaller angle results in what kind of doppler shift?
Smaller angle results in BIGGER doppler shift. (0 degrees is the max and 90 degrees is nothing)
What happens when you scan at 90 degree angle?
At 90 degree there is NO doppler shift. You are inside the vessel
Doppler equation formula
Fd= 2 x operating frequency x velosity x cosine theta/ prop speed
Define doppler equation and their relationship with one another
Doppler equation relates to the variables that result in doppler shift and is related to flow speed and frequency. When speed and frequency increase doppler shift increases.
What kind of relationship do doppler shift and angle have?
Doppler shift and angle have an inverse relationship.
What kind of relationship do angle and cosine theta have?
Angle and cosine theta are homies, what one does the other does too.
A stationary sound source and a stationary listener _____ result in doppler shift.
A stationary sound source and a stationary listener DO NOT result in doppler shift.
**THERE IS NO MOVEMENT. Doppler shift requires movement.
A doppler shift is a change in ______ of the ____ or ______ as a result of relative motion.
A doppler shift is a change in received frequency of the SOURCE or RECEPTOR as a result of relative motion.
A 3 MHZ transducer produces 2 Khz doppler shift frequency. If all parameters remain the same and we double operating frequency, what will be the new doppler shift?
Doubling operating frequency will double doppler shift.
Maximum negative doppler shift will be caused by the reflecftor which is ____ from the source
Maximum negative doppler shift will be caused by the reflector which is MOVING AWAY from the source
Maximum positive doppler shift will be caused by the reflector which is moving _____ the trandsducer
Maximum positive doppler shift will be caused by the reflector which is moving TOWARDS the transducer
The reflector which is ____ to the sound source will not produce any doppler shift.
The reflector which is PERPINDICULAR (90 degrees) to the sound souce will not produce any doppler shift
What are the limitations for color doppler?
Color doppler limitations are ...
Increased dwell time due to multiple pulses per scan line
Decreased frame rate to increase packet size
aliasiing seen in form of mosaics
What is aliasing?
Aliasing is color artifact due to improper settings. Aliasing occurs when doppler shift exceeds the nyquist limit (1/2 PRF). Aliasing is AKA undersampling
List the reasons for aliasing
Aliasing occurs due to ...
Scanning deep samples
Higher frequency selected than necessary
Improper doppler shift (results in low angle)
Undersampling
Exceeding nyquist limit
List the ways to reduce aliasing
Reduce aliasing by...
Scanning shallower
increase scale (PRF)
Lower frequency
Increase scanning angle
Use a smaller sample size (will increase frame rate)
Switch to CW doppler (requires no PRF)
What is auto correlation?
Auto correlation is the automatic assignment of color according to strength. Done by the machine.
What is power doppler used for?
Power doppler is used to indicate the prescence or abscence of flow in small.tiny vessels (does not alias)
List the limitations of power doppler.
Power doppler cannot tell you the type of flow, direction of flow or velosity (speed) of flow
List the differences between PW and CW
PW has 1 crystal, CW has 2
PW has damping and PRF, CW does not
PW has aliasing @ high velocity, CW has NO aliasing
PW has image and waveform, CW has waveform only
PW has a duty factor of 1%, CW is 100%
PW has range resolution, CW has range ambuiguity
What are the drawbacks of CW?
Drawback of CW...
No Image
Blind modality
Too much information/overlapping
Do you see any color at 90 degrees? which one?
At 90 degrees you do not see red or blue, you will only see black
What does lack of color indicate?
Lack of color indicates ...
Abscence of flow
poor probe position
occulded vessel
poor color gain
high wall filter setting
poor angle (90 degree)
Define spectral broadening.
Spectral broadening are wide spectral traces indicating multiple velocities are present in the sample. Vertical thickening of spectral trace. Spectral broadening is seen at stenosis and is AKA window filling.
What is Fast Fourier Transform?
FFT is the mathematical technique the ultrasound machine uses to calculate the doppler shift in spectral instruments. It shows the individual velosities in the signal. It is the PW & CW demodulation for spectral analysis
What is the unit for Viscosity?
The unit for viscosity is POISE
Pulsatile flow is controlled by ______
Pulsatile flow is controlled by the HEART
Phasic flow is controlled by _____
Phasic flow is controlled by RESPIRATION