The reflection of ultrasound waves at the air-skin interface is 100%, but if we use a coupling medium such as gel the beam reflection is reduced to only 0.1%.
This is the reason why a coupling gel must be used during ultrasound treatment. The gel must be neutral and should not contain any saline solution (the one used for diagnostic ultrasound is ideal). Prior to treatment a layer of gel should be spread on the hand probe surface and directly on the area to treat; the procedure should be repeated during treatment in order to help ultrasound penetration and the hand probe smooth sliding on the area to treat.
Biological tissues with a high fluid content absorb ultrasound waves better than less hydrated tissues.
Ultrasound waves generated by high frequency 1-3 MHz ultrasound devices are very easily absorbed by superficial tissues and consequently deeper tissues remain unaffected. In fact ultrasound waves absorption increases as the operating frequency increases.
This is one of the major advantages offered by EQultrasound (38 kHz) over traditional high frequency (1-3 MHz) ultrasound devices: since EQultrasound operates at a much lower frequency than traditional high frequency devices, it can reach deeper equine tissues and structures with limited absorption by superficial tissues.