Widely used – uses high frequency inaudible sound (acoustic energy) to produce thermal and mechanical effects in tissues generates deep heat
Ultrasound is generated as by piezoelectric effect -
Effects of ultrasound on tissues:
2) Mechanical a) Cavitation – expansion and contraction of gas bubbles in tissues oscillation micromassage
b) Acoustic streaming – movement of fluids or ions across membranes
Soft tissue injury, contusion, muscle spasm – especially for deep tissues
Infection; acute inflammation or acute phase of injury; deep vein thrombosis; peripheral vascular disease; tumours; haemophilia; metal implants; fractures; pregnancy;
Methods of application:
Continuous – used for thermal effects in tissues increase deep tissue temperature and collagen extensibility
Pulsed/interrupted – used for mechanical effects in tissues use when heat is contraindicated (eg acute phase).
Ultrasound does not propagate through air need a coupling medium that has a low attenuation (absorption) coefficient
Use gel; ultrasound head is placed directly on skin
Water immersion coupling:
Foot and ultrasound head used under water; head is directed at foot from about 2-3cm – indicated if direct contact with skin is contraindicated.