Ultrasound is a therapeutic modality that has been used by physical therapists since the 1940s. Ultrasound is applied using a round-headed probe or tube is placed in direct contact with the patient’s skin. Ultrasound gel is used on all surfaces of the head, in order to reduce friction and assist in the transmission of ultrasound waves. Therapeutic ultrasound is in the frequency range of about 0.8-1.0 MHz
The waves are generated by a piezoelectric effect caused by the vibration of crystals in the head of the wand / probe. The sound waves that pass through the skin cause a vibration of the tissues. This vibration or cavitation can cause a deep heating locally though usually no sensation of heat will be felt by the patient. In cases where a heating effect is not desirable, as a new injury with acute inflammation, the ultrasound can be pulsed continuously instead of transmission.
Ultrasound can produce many effects other than just the potential heating effect. It has shown it can cause increases in tissue relaxation, local blood flow, and scar tissue breakdown. The effect of increased local blood flow can be used to help reduce local swelling and chronic inflammation, and according to some studies, promote bone fracture healing. The intensity or power density of ultrasound can be adjusted depending on the desired effect. A higher power density (measured in watt/cm2 is often used in cases where scar tissue breakdown is the goal. (more…)
