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.
What is Ultrasound?
In ultrasound, the following events happen:
- The ultrasound machine transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe.
- The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).
- Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected.
- The reflected waves are picked up by the probe and relayed to the machine.
- The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (5,005 ft/s or1,540 m/s) and the time of the each echo's return (usually on the order of millionths of a second).
- The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image like the one shown below.
In a typical ultrasound, millions of pulses and echoes are sent and received each second. The probe can be moved along the surface of the body and angled to obtain various views.