Study guide for 18, 19, 20 Flashcards
Movement of fluid from one location to another?
Velocity
Fluid moving with a variable velocity accelerates and decelerates?
Pulsitile flow
Movement of fluid from one location to another that accelerates and decelerates w/ respiration?
Phasic Flow
Flow pattern seen with normal physiological states?
Laminar Flow
Chaotic flow in many directions and speeds?
Turbulent Flow
Frictional loss, blood slide along vessel wall is considered what?
Heat?
Reynolds number, turbulent flow?
> 2,000
What the effects of stenosis are?
change in flow direction ↑ velocity as vessels narrows turbulence downstream from the stenosis pressure gradient across the stenosis loss of pulsatility
Next 5 questions are about hydrostatic pressure?
These are all in supine
Ankle 140mmHg heart 0mmHg 140 mmHg (140 + 0)
Knee ‘’
mid Chest ‘’
Top of head’’
Doppler shift provide info about what?
Velocity
Positive and negative Doppler shift?
Positive
toward transducer
reflected higher than transmitted
arterial
Positive and negative Doppler shift?
Negative
away from transducer
reflected lower than transmitted
venous
Typical range of Doppler shift found in imaging examinations?
Audible
20Hz - 20kHz
If the sample volume is deep, the PRF and Nyquist limit is what?
low, creates aliasing
Phenomenon high velocity is negative?
Aliasing
Five ways to eliminate aliasing?
- adjust scale
- shallower
- ↓ frequency
- Baseline
- Continuous Wave
Large and small sample volumes, which will fill in on Doppler?
Large, spectral broading
X and Y axis on Doppler Spectrum?
X
Time
X and Y axis on Doppler Spectrum?
Y
Shift or Velocity
Doppler shift inversely related to?
speed of sound in the medium
What is the basic Doppler system that simple identifies the blood flow of the presence of a frequency shift?
power doppler (MW pg 333)
Gray shades on Doppler spectrum related to two things?
amplitude of reflected signal
number of blood cells creating the reflection
Doppler Spectrum, high waveform is a high frequency or low?
?
I think this is high freq. because they are directly related (MW pg 308)
What is the Doppler Effect?
the change in frequency
Difference between speed and velocity?
Speed
magnitude (distance red blood cells travel in 1 second)
Difference between speed and velocity?
Velocity
Magnitude and direction
Angle w/ Doppler/ No angle?
0⁰: 1.0
90⁰: 0
180⁰: -1.0
Primary advantage for a pulse wave Doppler?
select exact location
range resolution, range specificity
Primary advantage for continuous Doppler?
ability to accurately measure very high velocity
Bidirectional, type of processing?
Phase quadrature or quadrature detection
FFT used in what type of what?
Is a computer-based technique, is use to process both pulsed and continuous wave Doppler signals
Velocities that color flow measures?
mean or average
Autocorrelation?
digital technique to analyses color flow Doppler less accurate but faster than FFT
Limitation to color flow imaging?
it has range resolution and is subject to aliasing
pg 325 and esp physics pdf
Area of integration in Doppler is called?
Sample Volume
More accurate velocity measurement
Increased sensitivity low flow
Large Doppler packet advantages and disadvantages?
Advantages
More time needed to acquire data
Reduced frame rate
Decreased temporal resolution
Large Doppler packet advantages and disadvantages?
Disadvantages
How to measure low flow states?
Power Doppler?
Inspiration vs Expiration
Inspiration
Diaphragm ↓ Thoracic pressure ↓ Abdomen pressure ↑ Venous return to the heart ↑ Venous flow in legs ↓
Inspiration Vs Expiration
Expiration
Diaphragm ↑ Thoracic pressure ↑ Abdomen pressure ↓ Venous return to the heart ↓ Venous flow in legs ↑
Venous pressure is low, pressure in veins?
Low
- What happens to shape of veins when pressure increases?
starts hourglass, then goes oval, then to round
Hydrostatic pressure when standing
Ankle 140 mmHg, Far below heart level, 100mmHg , 240mmHg (140 + 100)
Knee, 140mmHG, Somewhat below heart
