LECTURE 17

Question 1

PRESENTATION OF FLOW INFORMATION IN COLOR, SUPERIMPOSED ON A 2D GREY SCALE IMAGE.

Answer 1

COLOR DOPPLER

Question 2

• 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

Answer 2

HOW COLOR DOPPLER IS ACHIEVED.

Question 3

NUMBER OF US PULSES PER LINE OF COLOR

Answer 3

PACKET SIZE

TYPICAL SIZE: 8-30

Question 4

LARGER PACKET SIZES:

Answer 4

• BETTER VELOCITY MEASUREMENTS
• BETTER COLOR SENSITIVITY
• WORSE TEMPORAL RES. (DECREASED FRAME RATE)

Question 5

SMALLER PACKET SIZES:

Answer 5

• WORSE VELOCITY MEASUREMENTS
• WORSE COLOR SENSITIVITY
• BETTER TEMPORAL RES.

Question 6

INFORMATION YIELDED FROM COLOR DOPPLER:

Answer 6

• PRESENCE OF FLOW
• FLOW DIRECTION
• REFLECTOR VELOCITY (QUALITATIVE)
• REFLECTOR VARIANCE

Question 7

ADVANTAGES OF COLOR DOPPLER:

Answer 7

• 2D INFO
• FACILITATES EXAM.
• PROVIDES: DIRECTION, CHARACTER, RELATIVE VELOCITIES, AMPLITUDE OF FLOW

Question 8

DISADVANTAGES OF COLOR DOPPLER:

Answer 8

• POORER TEMPORAL RES.
• ALIASING
• CANNOT MEASURE EXACT VELOCITIES

Question 9

REASONS FOR COLOR ALIASING:

Answer 9

• HIGH VELOCITIES

- COLOR SCALE SETTING TOO LOW

Question 10

METHODS OF DISPLAYING COLORS IN RELATION TO VELOCITY INFO.

Answer 10

COLOR ASSIGNMENT MAPS

VELOCITY AND VARIANCE

Question 11

• DARKER, DULLER COLORS = SLOWER VELOCITIES.

- BRIGHTER, LIGHTER COLORS = FASTER VELOCITIES.

Answer 11

VELOCITY MAP

Question 12

• EXTRA COLOR ADDED (USUALLY GREEN)
• INCREASE OF VARIANCE = BRIGHTNESS OF GREEN INCREASES
• GREEN = DISTURBED, TURBULENT FLOW
• USED IN CARDIAC IMAGING

Answer 12

VARIANCE MAP

Question 13

• USED FOR COLOR DOPPLER
• CALCULATES AVERAGE SHIFT OF ECHOS FROM SAME PACKET.
• SIMILAR TO FFT (NOT AS ACCURATE BUT FASTER)
• QUALITATIVE INFO.

Answer 13

AUTOCORRELATION!!!

AKA PHASE SHIFT AUTOCORRELATION.

Question 14

• NEWER METHOD OF DOPPLER SHIFT ANALYSIS
• FASTER THAN FFT
• CAN PINPOINT SPECIFIC ECHO OUT OF MANY IN TIME

Answer 14

TIME DOMAIN PROCESSING

Question 15

COLOR POWER DOPPLER AKA

Answer 15

COLOR DOPPLER ENERGY
ULTRASOUND ANGIO
COLOR POWER ANGIO

Question 16

DIFFERENCES BETWEEN COLOR DOPPLER AND POWER DOPPLER:

Answer 16

POWER DOPPLER:

• ESTIMATES POWER OF DS WITHIN SPECIFIC REGION
• POWER OF SHIFT RELATES TO CONCENTRATION OF RBCs (REFLECTOR)
• INFO BASED ON STRENGTH OR POWER OF REFLECTORS, NOT VELOCITY

Question 17

ADVANTAGES OF POWER DOPPLER:

Answer 17

1. NOT ANGLE DEPENDANT
2. NOT SUBJECT TO ALIASING.
3. GREATER SENSITIVITY TO FLOW.

Question 18

DISADVANTAGES OF POWER DOPPLER:

Answer 18

1. NOT DIRECTION SENSITIVE
2. CANNOT DETECT VELOCITY
3. CANNOT DEPICT FLOW CHARACTERISTICS
4. MORE TIME
5. FLASH ARTIFACTS