Ultrasound application
Therapeutic ultrasound is proposed to deliver energy to
deep tissue sites through ultrasonic waves, to produce
increases in tissue temperature or non-thermal physiologic
changes [19]. Unlike ultrasound for medical imaging
(which transmits ultrasonic waves and processes a
returning echo to generate an image), therapeutic ultrasound
is a one-way energy delivery which utilises a crystal
sound head to transmit acoustic waves at 1 or 3 MHz
and at amplitude densities between 0.1 and 3 W/cm2
[16,19]. Ultrasonic energy causes soft tissue molecules to
vibrate from exposure to the acoustic wave. This
increased molecular motion generates frictional heat,
thus increasing tissue temperature. Referred to as ultrasound’s
“thermal effects”, this heating is proposed to
increase collagen extensibility, increase nerve conduction
velocity, alter local vascular perfusion, increase enzymatic
activity, alter contractile activity of skeletal muscle, and
increase nociceptive threshold