Ultrasound and its therapeutic benifits
Therapeutic ultrasound refers generally to any type of procedure that uses ultrasound for therapeutic benefit. This includes HIFU, lithotripsy, targeted ultrasounddrug delivery, trans-dermal ultrasound drug delivery, ultrasound hemostasis, and ultrasound assisted thrombolysis.
Therapeutic ultrasound in physical therapy is alternating compression and rarefaction of sound waves with a frequency of >20,000 cycles/second. Therapeutic ultrasound frequency used is 0.7 to 3.3 MHz. Maximum energy absorption in soft tissue is 2 to 5 cm. Intensity decreases as the waves penetrate deeper. They are absorbed primarily by connective tissue: ligaments, tendons, and fascia (and also by scar tissue).
Therapeutic ultrasound may have two types of benefit: Thermal effects and non thermal effects. Both use sound waves generated through a transducer head (which looks a bit like a microphone) to penetrate soft tissues. The difference between the two types of ultrasound therapy is the rate at which the sound waves penetrate the tissues.
- Thermal ultrasound therapy. Thermal ultrasound therapy uses a more continuous transmission of sound waves. The sound waves cause microscopic vibrations in the deep tissue molecules, increasing heat and friction. The warming effect encourages healing in the soft tissues by increasing the metabolism at the level of the tissue cells.
- Mechanical ultrasound therapy. Mechanical ultrasound therapy uses pulses of sound waves to penetrate tissues. While this still has a minor warming effect on the tissues, it also causes expansion and contraction in the tiny gas bubbles of the soft tissues. This helps to decrease the inflammatory response, reducing tissue swelling and thus decreasing pain.
Thermal effects are due to the absorption of the sound waves. Non thermal effects are from cavitation, microstreaming and acoustic streaming. Cavitational effects result from the vibration of the tissue causing microscopic air bubbles to form, which transmit the vibrations in a way that directly stimulates cell membranes. This physical stimulation appears to enhance the cell-repair effects of the inflammatory response.
Therapeutic ultrasound is sometimes recommended for muscle as well as joint pain.
Ultrasound has been used in various drug delivery applications to enhance the delivery of pharmaceuticals to target tissues (Acoustic Targeted Drug Delivery). Ultrasound has been shown to facilitate the delivery of drugs across the skin, promote gene therapy to specific tissues, deliver chemotherapeutic drugs into tumours and deliver thrombolytic drugs into blood clots. In addition, ultrasound has also been shown to facilitate the healing of wounds and bone fractures.
The type of ultrasound therapy you receive depends on your condition. If you have myofascial pain, or had a muscle strain or sprain that has not healed, your therapist will likely use thermal ultrasound therapy. If your pain is caused by scar tissue or swelling, such as with carpal tunnel syndrome, you may benefit more from mechanical ultrasound therapy.
How Ultrasound Therapy Is Performed
Your therapist will select a small surface area to work on for anywhere from five to 10 minutes. Gel is applied either to the transducer head or to your skin, which helps the sound waves evenly penetrate the skin. During your ultrasound therapy treatment, your therapist will continually move the transducer head over and around the selected area.