Ultrasound

Question 1

General Principles

Answer 1

Acoustic form of radiant energy

High frequency acoustic vibrations

Question 2

Absorption of Ultrasound

Answer 2

tissues that absorb more energy will heat faster
ex. high water content = low absorption rate
high protein content = high absorption rate
Absorption rate:
(greatest) bone>nerve>muscle>fat (lowest)
more dense the tissue, the faster the sound waves move

Question 3

When sound waves encounter a boundary

Answer 3

1) Transmitted- no significant loss of energy.
2) Refraction- energy is altered and changes direction slightly
3) Reflection-energy bounces back toward the energy source

Question 4

Thermal/heating effects

Answer 4

1. Increases blood flow with dilation of blood vessels
2. Increased extensibilty of soft tissue
3. Increased viscosity of fluid w decreased joint stiffness
4. Decrease pain
5. Increase metabolic rate
6. Decrease muscle spasm

Question 5

Nonthermal effects

Answer 5

1. Cavitation- formation of gas bubbles that expand and compress causing pressure changes in tissue fluids.
   Stable cavitation- bubbles expand and contract. will cause increased blood flow to area
   Unstable cavitation- bubbles implode and collapse, increase pressure to point where tissue damage may occur
2. Microstreaming- unidirectional movement of fluid along boundary of cell membranes
   alters cell permeability to Na and K.
   Fibroblast activity is stimulated. increase protein synthesis, tissue regeneration and blood flow