Acoustically transparent materials

[azeltwanger]

Does anyone know of an acoustically transparent solid material that can be used in between an ultrasonic ablation transducer and target tissue? Essentially, I'd like to find something whose material properties minimize scattering/diffusion and heating. I know that there will be a loss due to reflection/refraction, and I'm wondering if there are any specialized materials that can minimize it.

I appreciate your help!