Ultrasonido

1. Basic Ultrasound Physics
V0805

2. Outline
• Ultrasound
– Sound
– Transducer
– Advantages
• Imaging modes
– M
– B
– CW
– PW
– Color
– Power

3. Sound
Frequency
Infrasound Audible Sound Ultrasound
20Hz 20kHz
For medical diagnostic imaging
1MHz 20MHz
Low High

4. Advantages
• Cheap
• Simple
• Non-radiation (for OB/GYN application)
• Real-time (for cardiac application)
• Repeat
• Non-invasive

5. M Mode
M: Motion
displayed over time
Time
Depth
Function: to display tissue motion 1950s

6. B Mode
B: Brightness
• displayed as dots on screen
• stronger signal, brighter dot
Function: to display tissue structure
B mode is also called 2D
mode.
1950s

7. B Mode
Convex Probe
Linear
Convex
Phased array probe
Linear probe

8. CW Mode (continuous wave)
CW: Continuous-Wave
Doppler
speed of blood cells
displayed on a
time/velocity graph
Function: to measure velocity of blood flow, especially in heart
Time
Velocity
1956

9. CW Mode
Sensitive Region
Angle Correction
Sample Line
Gray scale stands for:
the amount of all objects
in that velocity
along the sample line.

10. Principle of CW
Some elements are transmitting
sound waves.
The transmitting and receiving
of sound waves are JUST in the
same time.
But there is a sensitive region.
The others are receiving.
There is NO Sample Volume.

11. PW Mode (continuous wave)
PW: Pulse-Wave
Doppler
Function: to measure velocity of blood flow
Time
Velocity
1959

12. PW Mode
Sample Volume
Angle Correction
Sample Line
Gray scale stands for:
the amount of all objects
in that velocity
in the sample volume.

13. Principle of PW
Elements are both transmitting
and receiving sound waves.
The transmitting and receiving
of sound waves are NOT in the
same time.
There is a Sample Volume.
PRF: Pulse Repetition Frequency
Transmit Receive Transmit Receive …

14. Color Mode
Color Doppler:
Pixels assigned color
based on mean velocity
Function: to display direction of blood flow
Color mode is also called
CDFI mode (Color Doppler
Flow Imaging) or CFM
(color flow mapping)
Red towards probe
Blue away from probe
1983

15. Power Mode
Power Doppler:
Pixels assigned color
based on mean power
Function: to display volume of blood flow, especially at low velocity
Power mode is also
called CPA mode.
(Color Power Angio)

16. Color Maps
Gray Scale Velocity Power Directional
Power
B mode Color mode Power mode

17. Difference-Color & colorize
B mode - colorized Color mode
Whole image is colorized. Only blood flow is colorized.
Tissue is monochrome.

18. Difference-Color & Power
Sensitivity
Direction
Velocity
Angle dependent
Application
Yes
Yes
Yes
Normal velocity
No
No
No
Low velocity
Normal High
Color Power
Yes
No
No
Low velocity
High
DirPower
Power Doppler displays amplitude of signal (how much)
Color Doppler displays velocity (how fast)

19. Angle Dependent
Color mode
vertical oblique
Power mode
Angle Dependent Yes No
At perpendicular angle No flow displayed Displayed normally

20. Difference-PW & CW
Principle
Probe
Velocity
Locate
Application
All elements are transmitting
and receiving sound waves.
All
Low
Sample volume
All
Phased array, pencil, other
High
Sample line
Cardiology
Pulsed-wave Continuous wave
PW mode CW mode
Some elements are
transmitting sound waves.
The others are receiving.
Sample Volume
Angle Correction
Sample Line
Sensitive Region
Angle Correction
Sample Line

21. Panoramic Imaging

22. Panoramic Imaging

23. 3D/4D Imaging