How Ultrasound Works

By: Craig Freudenrich, Ph.D.  | 
Pregnancy Image Gallery ­Enedino Ortega, four months pregnant, lies on a bed as Zaditza Silveira uses an ultrasound machine to take images of her baby at the Birthing Center of South Florida. See more pregnancy pictures.
Joe Raedle/Getty Images­

­There are ma­ny reasons to g­et an ultrasound. Perhaps you're pregnant, and your obstetrician wants you to have an ultrasound to check on the developing baby or determine the due date.

Maybe you're having problems with blood circulatio­n in a limb or your heart, and your doctor has requested a Doppler ultrasound to look at the blood flow. Ultrasound has been a popular medical imaging technique for many years.


Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines.

­In this article, we'll look at how ultrasound works, what type of ultrasound techniques are available and what each technique can be used for.