Therapeutic Ultrasound
Therapeutic Ultrasound involves stimulation outputs in the range of 1 - 3 MHz. It has been used for decades in the physical therapy setting for many indications including: bursitis, muscle strains (acute & chronic), various contusions, tendinitis (acute & chronic), ligament sprains, etc.
The lower frequencies (1MHz) are used where deeper tissue penetration is desirable while the higher frequencies (3MHz) are suited for more superficial indications.
Some manufacturers provide dual-frequency treatment heads that allow for both 1MHz and 3MHz outputs from a single head.