LECTURE 17 Flashcards
1
Q
PRESENTATION OF FLOW INFORMATION IN COLOR, SUPERIMPOSED ON A 2D GREY SCALE IMAGE.
A
COLOR DOPPLER
2
Q
- FORM OF PULSED DOPPLER
- MULTIPLE PULSES DOWN SCAN LINE
- INFO TAKEN FROM LOCATIONS ALONG EACH LINE
- INFO COMPOSITED TO YIELD IMAGE OF AREA OF INTEREST
A
HOW COLOR DOPPLER IS ACHIEVED.
3
Q
NUMBER OF US PULSES PER LINE OF COLOR
A
PACKET SIZE
TYPICAL SIZE: 8-30
4
Q
LARGER PACKET SIZES:
A
- BETTER VELOCITY MEASUREMENTS
- BETTER COLOR SENSITIVITY
- WORSE TEMPORAL RES. (DECREASED FRAME RATE)
5
Q
SMALLER PACKET SIZES:
A
- WORSE VELOCITY MEASUREMENTS
- WORSE COLOR SENSITIVITY
- BETTER TEMPORAL RES.
6
Q
INFORMATION YIELDED FROM COLOR DOPPLER:
A
- PRESENCE OF FLOW
- FLOW DIRECTION
- REFLECTOR VELOCITY (QUALITATIVE)
- REFLECTOR VARIANCE
7
Q
ADVANTAGES OF COLOR DOPPLER:
A
- 2D INFO
- FACILITATES EXAM.
- PROVIDES: DIRECTION, CHARACTER, RELATIVE VELOCITIES, AMPLITUDE OF FLOW
8
Q
DISADVANTAGES OF COLOR DOPPLER:
A
- POORER TEMPORAL RES.
- ALIASING
- CANNOT MEASURE EXACT VELOCITIES
9
Q
REASONS FOR COLOR ALIASING:
A
- HIGH VELOCITIES
- COLOR SCALE SETTING TOO LOW
10
Q
METHODS OF DISPLAYING COLORS IN RELATION TO VELOCITY INFO.
A
COLOR ASSIGNMENT MAPS
VELOCITY AND VARIANCE
11
Q
- DARKER, DULLER COLORS = SLOWER VELOCITIES.
- BRIGHTER, LIGHTER COLORS = FASTER VELOCITIES.
A
VELOCITY MAP
12
Q
- EXTRA COLOR ADDED (USUALLY GREEN)
- INCREASE OF VARIANCE = BRIGHTNESS OF GREEN INCREASES
- GREEN = DISTURBED, TURBULENT FLOW
- USED IN CARDIAC IMAGING
A
VARIANCE MAP
13
Q
- USED FOR COLOR DOPPLER
- CALCULATES AVERAGE SHIFT OF ECHOS FROM SAME PACKET.
- SIMILAR TO FFT (NOT AS ACCURATE BUT FASTER)
- QUALITATIVE INFO.
A
AUTOCORRELATION!!!
AKA PHASE SHIFT AUTOCORRELATION.
14
Q
- NEWER METHOD OF DOPPLER SHIFT ANALYSIS
- FASTER THAN FFT
- CAN PINPOINT SPECIFIC ECHO OUT OF MANY IN TIME
A
TIME DOMAIN PROCESSING
15
Q
COLOR POWER DOPPLER AKA
A
COLOR DOPPLER ENERGY
ULTRASOUND ANGIO
COLOR POWER ANGIO
