Because the frequency of medical ultrasound is 2.5-5M, it cannot be conducted in the air. If there is air in the probe and skin, the ultrasonic wave will return as soon as it meets the air, and will not enter the human body, so it will not play a role in inspection. The air between the probe and the skin can be eliminated by first coating a layer of coupling agent on the skin.

First, the concept of ultrasonic coupling agent

During ultrasonic examination, the air between the probe and the patient's skin will hinder the transmission of ultrasonic waves into the human body. In order to obtain high-quality images, liquid conductive medium is needed to connect the probe with the patient's body surface. This medium is the coupling agent.

Second, the reasons for using ultrasonic coupling agent

The purpose of using ultrasonic coupling agent is to fill the tiny gaps between contact surfaces first, so as to avoid the tiny air between these gaps from affecting ultrasonic penetration; Secondly, the "transition" effect of the coupling agent reduces the acoustic impedance difference between the probe and the skin, thus reducing the reflection loss of ultrasonic energy at the interface. In addition, it also plays the role of "lubrication", reducing the friction between the probe surface and the skin, so that the probe can slide and explore flexibly.

Thirdly, the influence of ultrasonic coupling agent on image.

Coupling agent is closely related to the quality of ultrasonic images obtained. Poor quality coupling agent will cause ultrasonic energy loss, reduced resolution, blurred image, even skin irritation and damage to the probe.