TCD is a noninvasive and painless ultrasound technique that uses sound waves to evaluate blood flow (blood circulation) in and around the brain. There is no special contrast or radiation involved in the test.

Physicians recommend this test to determine if there is anything happening in the blood vessels that is affecting blood flow to the brain. Transcranial Doppler ultrasound is often the test of choice for:

• Vasospasm, following a ruptured brain aneurysm
• Sickle cell anemia, to determine a patient's stroke risk
• Ischemic stroke
• Intracranial stenosis or blockage of the blood vessels
• Cerebral microemboli
• Patent Foramen Ovale, a hole in the heart that doesn't close properly after birth

At Cedars-Sinai, TCD ultrasounds are used to evaluate the 13 major arteries supplying blood flow to the brain, but there are other TCD studies used to identify specialized problems related to brain blood flow:

• Embolic detection monitoring
  This test detects any free-floating particles that may be in the bloodstream. These particles can be a significant source of stroke risk.
• Agitated saline bubble study
  This test is specific for identifying whether there is a passageway or hole between the right and left chambers through which blood enters the heart. This hole usually closes after birth. If it doesn't close, it can be a source of increased stroke risk in certain patients.
• CO2 vasomotor reactivity study
  This noninvasive study looks at whether the small vessels that regulate blood flow to the brain are working properly. When a small amount of carbon dioxide (CO2) and oxygen are inhaled, similar to holding one's breath, these small vessels should widen and increase blood flow to the brain. When a person hyperventilates, the vessels should shrink and slow blood flow to the brain.

Cedars-Sinai relies on transcranial Doppler expert Brenda Rinsky, RDMS.