Ultrasound therapy is a type of deep-heating treatment for soft tissue injuries, which primarily increase the rate at which tissue heals. Ultrasound therapy can also be used to administer medication under the skin in a process called phonophoresis. An ultrasound machine emits high frequency sound waves that permeate the soft tissue of the body and promote its healing. Therefore, it can be an effective treatment for athletic injuries.
Because ultrasound therapy emits sound waves at such a high frequency, they cannot be transmitted through air; rather a medium, like gel or water, is used. Ultrasound treatments are beneficial, but there are times when it is not appropriate. As an example, patients suffering from sensory deficits, poor circulation, cancerous tumors and fractures, as well as pacemaker users, cannot have ultrasound treatment. As a result, ultrasound treatments must be administered by trained, healthcare professionals.
The heating rate and depth that the energy reaches are determined by the frequency. The parameter of frequency for ultrasound treatment is measured in megahertz, MHz, which is "one million cycles per second." One MHz affects tissue that is approximately 2 inches deep and 3 MHz effects tissue that is approximately 1/4 inch deep.
The duty cycle is the determining parameter for the ultrasound's thermal effects. As an example, if the machine is set to continuous output it will generate heating effects, but if it is set to pulsed output, it focuses on non-heating effects. Whether thermal effects are a desired rehabilitation goal or not is determined by the injury's stage of healing. Thermal effects are used in athletic training to treat conditions like bursitis and low back pain.
The amount of energy, or its intensity, transmitted from the ultrasound machine is measured in watts. The number in watts indicates the strength of the sound waves. Typically, ultrasound treatments are given at an intensity of 0.3 to 5 watts.
The duration of ultrasound treatment is determined by the size of the targeted structure, the intensity used and the specific treatment goals. If the frequency is set at 1 MHz, the duration is between 10 and 12 minutes. If the frequency is set to 3 MHz, the duration is between three to four minutes. Generally, ultrasound treatments continue for 10 to 14 days.
- "Therapeutic Modalities"; Chad Starkey; 2004
- "Emerging Therapeutic Ultrasound"; Junru Wu, et al.; 2006