Preparation for a dating ultrasound
High-frequency sound waves travel from the probe through the gel into the body. A computer uses those sound waves to create an image.
Ultrasound exams do not use radiation (as used in x-rays).
One or more frames of the moving pictures are typically captured as still images. The movement of the embryo or fetus and his or her heartbeat can be seen as an ongoing ultrasound movie.
Ultrasound devices also use Doppler, a special application of ultrasound, which processes echoes produced by blood flowing through the fetal heart, blood vessels and umbilical cord and turns them into audible sound.
Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships and fishermen.
This sound has been described by patients as a whooshing noise.
Doppler ultrasound, a special ultrasound technique, measures the direction and speed of blood cells as they move through vessels.
Because images are captured in real-time, they can show the structure and movement of the body's internal organs.
They can also show blood flowing through blood vessels.