Definition: During use of ultrasound the space between the transducer & the site of the lesion of the patients is filled with thin layer of a coupling fluid which will allow the transmission of sonic energy. This is called coupling media.
Usefullness: Ultrasound energy is propagated as longitudinal waves & at this frequency a coupling agent is required between the body & the vibrating source. There has to be intimate contact between the transducer head of the machine & the body surface to allow maximum transfer of energy from the head to the tissue. Even minute amounts of air can disrupt the flow of energy.
Criteria: Coupling media should have their high sound transmissivity. They should have negligible absorptivity powers & be viscous so that they stay on the skin during treatment.
Amount: Only a thin film of couplant should be used because too much & too little coupling reduces transmissivity.