An ultrasound machine, which is very commonly used in physical therapy, works by using high frequency sound waves (that can’t be heard by the human ear) to effectively treat deep tissue injuries. Therapeutic ultrasound is in the frequency range of 0.9 -3Mhz and it is used either as a continuous or intermittent sound wave with varying frequency depending on the nature of the injury. By using different frequencies, physical therapists can target tissues at different depths for healing or pain relief. By varying the frequency from continuous to intermittent (also known as pulsed frequency) the physical therapist can control the amount of heat applied from the ultrasound.
Ultrasound is applied by using either ultrasonic aqueous gel or water between the sound head and the body part being treated. The sound head is slowly and continuously moved around by the physical therapist over the affected area, which is normally no larger than 5-10 cm in diameter, and treatment usually lasts for about five minutes.
Ultrasound is often used in conjunction with soft tissue massage, stretching and passive mobilization techniques as the deep heat from the ultrasound effectively warms up muscles so they are more relaxed and better results can then be achieved with manual therapy. Ultrasound waves penetrate deeply into the tissued because the sound waves are attracted to tissue with high water content such as muscle and bone. Other forms of heat treatment (such a warm wheat bag) may not penetrate as deeply as ultrasound and serve only to warm up superficial soft tissue layers. The therapeutic effects of heat through ultrasound include relief of pain and muscle spasm and increased blood supply can promote faster healing rates.
Therapeutic ultrasound is beneficial for the following soft tissue injuries both for its therapeutic heat benefits and its ability to speed up the healing process by increasing blood supply and helping recirculate inflammatory chemicals away from the area:
Ultrasound is also effective in speeding up the healing process of wounds by causing the cells to release histamine which is a chemical that accelerates the inflammatory phase of healing. Ultrasound also increases the production of collagen which promotes wound contraction and increases the strength of healing tissue.
Low intensity pulsed ultrasound is effective in significantly reducing healing time by promoting faster bone union in fractures. It is successfully used to quicken the return to sport of athletes after they sustain fractures. In contrast to the more frequently used higher intensity ultrasound, when using low intensity pulsed ultrasound, the sound head is kept stationary over the fracture site and treatment lasts for around 20 minutes about three times a week.
Ultrasound has also been successfully used in the treatment of mastitis in lactating women. The use of ultrasound before soft tissue massage of the breast effectively helps break down inflammation and it cause vasodilation of the blood vessels to help “flush out” and recirculate the inflammatory chemicals caused by the mastitis infection. The gentle deep warmth provided by the ultrasound treatment is also effective in pain relief of the sore breast.
Ultrasound cannot be used in some instances, such as over burns, with deep venous thrombosis, over malignancies, or if there is cardiac pacemaker in place or over the eyes. Your physical therapist will clear you of any contraindications before using ultrasound therapy if it is considered a suitable part of your treatment.
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