This allow for detection of thunderstorms by news weather Doppler. Doppler ultrasound examinations allow for the detection of blood flow and the determination of the speed and direction of the flow. Sound travels best through solid and liquids. That is why people used to put their ear on the railroad tracks to detect the trains prior to being able to hear them through the air. The gel eliminates the air between the transducer and the body.
All ultrasound machines come with a variety of transducers.
They can be thought of as prescription glasses. Each transducer focuses at a different level. Unfortunately not, no one test is perfect. In order to detect an abnormality, the abnormality must either distort the surrounding normal anatomy or cause the sound beam to travel at a different speed. Ultrasound does not use radiation to obtain an image.