Dear all, I have a quick question about the use of coupling gel in ultrasound imaging (of an unborn child as an example). As I understand it, if coupling gel were not used, as the ultrasound waves left the transducer, they would undergo a massive amount of reflection at the air-skin (body fat) boundary, due to the massive difference in densities which exists between the two media. Coupling gel ensures that this is not the case by helping to "balance out" this density difference. But what exactly is the density of the coupling gel? At first I thought it to be about the same as body fat, but would this again not lead to massive amounts of reflection as the ultrasound waves left the transducer and entered the gel? Is the density of coupling gel somewhere between that of body fat and air? Or indeed, is coupling gel used for another reason? Any and all help in helping to understand this would be greatly appreciated! Many thanks.