85. ULTRASOUNDS: MECHANICAL EFFECTS

Question 1

1. What do most of the Mechanical effects of Ultrasounds revolve around?

Answer 1

THEY REVOLVE AROUND THE:
- generation of micro bubbles within the tissue
- possible collapse of micro bubbles within the tissue

Question 2

2. What is Cavitation?

Answer 2

• this is the interaction between the Ultrasound beams
  and the micro bubbles

Question 3

3. What kind of pressures does a Sound Wave have?

Answer 3

1. POSITIVE PRESSURES
   
   • these are known as Compressional Pressures
2. NEGATIVE PRESSURES
   - these are known as Reflectional Pressures

Question 4

4. What will produce Micro-Bubbles?

Answer 4

• a negative pressure that is significantly large

THIS CAN ALSO ENLARGE:
- existing microbubbles

Question 5

5. What 3 factors affect the occurrence of Cavitation and how it behaves?

Answer 5

1. The Ultrasound Frequency
2. The Ultrasound Intensity
3. The Ultrasound Field Focusing

Question 6

6. What is Stable Cavitation associated with?

Answer 6

• it is associated with Micro streaming
• this can produce stress
• this stress can disrupt cell membranes

Question 7

7. What can cause a Violent Implosion to take place?

Answer 7

WHEN PRE-EXISTING BUBBLES
- or Cavitation Nuclei expand

THIS IS CAUSED BY:
- the negative pressures that are applied to them from
the Ultrasonic field

Question 8

8. Is there any sufficient evidence to state that diagnostic ultrasound exposure has caused any type of Cavitation in humans?

Answer 8

• no

Question 9

9. Does this diagram make sense?

Answer 9

• yes