Diagnostic imaging refers to a variety of non-invasive methods for identifying and monitoring diseases or injuries via the generation of images representing internal anatomic structures and organs of the patient's body.
Sound waves travel fastest through a solid material. The second fastest medium is a liquid, and the slowest medium is a gas, because sound waves travel by vibrating molecules in a medium. In solids,... Sound waves travel fastest through a solid material.
This is due to the fact light travels at 300,000,000m/s in all mediums(space,air water,etc), but sound travels at 340m/s in air but it's speed is different in others, for example it is actually quicker in water due to the particles being closer together.