Health Library

What Is an Ultrasound?

An ultrasound scan is a medical test that uses high-frequency sound waves to create live images from the inside the body. Also called a sonogram or sonography, ultrasounds let doctors see the body’s soft tissues, which X-rays can’t do.

Doctors order ultrasounds for many reasons, such as to look for the causes of pain, swelling, and infection. Ultrasound scans are safe and painless.

What Is a Transcranial Doppler Ultrasound?

A transcranial Doppler ultrasound uses sound waves to evaluate blood flow (blood circulation) in and around the brain. The test is also called transcranial Doppler (TCD) ultrasonography. This test takes a bit longer to do than other types of ultrasounds. A TCD can take between 30 minutes to 1 hour.

Why Are Transcranial Doppler Ultrasounds Done?

Doctors order transcranial Doppler ultrasounds to check blood vessels when a problem is affecting blood flow to the brain. For children and teens, they might order the test:

• to screen kids and teens with sickle cell disease for their risk of stroke
• if someone has signs of an ischemic stroke (when blood flow is blocked to part of the brain)
• to look for blocked or narrowed blood vessels
• if a child had a traumatic brain injury
• to check brain function

What if I Have Questions?

If you have questions about the transcranial Doppler ultrasound or what the test results mean, talk to your doctor.