Lecture 22 Flashcards
Signal processor detects
Direction
Mean
Variance
Power
Direction is based on
positive or negaative doppler shift
The average velocity of blood in an area is _______ and ________
Calculated and displayed
Variance is
The variety within the blood flow
Standard deviation
Power is
Strength or intensity of the echo
Related to amplitude
Power depends on
Reflectors- specular reflection vs. Scattering
Impedance- higher impedance mismatch = more reflection
Concentration of RBC’s - higher concentraion = more reflection
Autocorrelation is
Math technique for colour doppler
Done with signal processor
Determines mean and variance
Autocorrelation the are range of what pulses sent out per line and what is it usually
3-32
10-20
Ensemble length is
pulse/ scan line
More pulses are for
Accuracy of speed calculation
Sensitivity (picking out weaker echoes/ shifts - slow flow)
Once the instrument processes the doppler dat it goes to ____
Display
The display uses
Hue, staturation and luminance parameters
Hue
What colour is shown
Sturation is
The amount of colour
Luminance is
Echo intenstiy and power/ brightness
Similar to 2D echo intensity
Stronger echoes - brighter
Colour box/window
Can change the size - changes the coverage
Affects frame rate/ temp resolution
Colour map shows slower speeds at ______ and faster at ____________
Middle of dial
Top and bottom of dial
Colour map helps to interpret (3)
Mean velocities
Direction of flow/ sign
Variance - change in colour left to right
____ - _____ spectrum most commonly used
Red - blue
Red =
Positive shift (usually)
Blue=
Negative shift
Invert
Flips the colour map
Does NOT change the direction of flow
Simply adjust the representation
The carotid bifurcation above shows blood flow away from the transducer
We like arteries to be red
We can flip the colour map
Baseline is
Zero point (no doppler shift)
Can move the baseline up or down based on what you want to fit on your map
Eg. All my flow is positive, dont need as much blue
Cant control __________ in doppler
PRF
Not in 2D
Changing our PRF (kHz), we change our _________
Scale (cm/s)
We can pick up faster or slower ______ by increasing or decreasing PRF
speeds
Decreased PRF = ________ scale
Decreased
What happens if your scale is too high
Slower flows go undetected
What happens if your scale is too low?
Faster flows alias
Aliasing shows
Wrap around colour
