How is ultrasound used in the medical field?

Ultrasound is a form of mechanical energy, high frequency sound waves outside audible spectrum of human ear (from 16Hz to about 15-20,000 Hz).
In Medical field, ultrasound is used at:
- Non-invasive medical diagnostic
- Doppler ultrasound
- Three-dimensional ultrasound (3-D) with ultrasound processing in images  in 3-D space, or four-dimensional space (4-D).

Responding to the application of ultrasound:
- Thermal
- Mechanical
- Chemical.
All these effects of ultrasound are dependent on the dose of ultrasound!
Ultrasound energy has the following physiological effects:
1. inflammatory response and tissue recovery,
2. restoration quality 
3. the heating of the soft tissues.
Ultrasound energy is absorbed especially in tissues with high collagen: bone, periosteum, cartilage, ligaments, capsules, tendons, fascia, scar tissue, surface tissue.

Common use of ultrasounds for non thermal effect
Facilitate healing of inflammations and proliferative phase   after soft tissue injuries (tendinitis, bursitis, acute soft tissue injuries). Healing of bone lesions = 1.5 MHz, pulse 20%, 0.15w/cm2, 20 minutes daily.