Houston Methodist. Leading Medicine.
Houston Methodist. Leading Medicine

Methodist Cardiovascular Surgery Associates

Our Services - Diagnostic Technologies: Ultrasound

The Transcranial Imaging Center

The Transcranial Imaging Center is a dedicated diagnostic imaging program, run by Dr. Zsolt Garami under the direction of Methodist Cardiovascular Surgery Associates, for performing non–invasive examinations of cerebrovascular blood circulation (blood flow in and around the brain). The primary testing methods are transcranial Doppler (TCD), transcranial color–coded duplex (TCCD), and carotid duplex. TCD uses Doppler technology, similar to the technology used for weather measurements, to measure blood circulation by peering through naturally occurring windows in a person’s skull. Considered the "doctor’s stethoscope for the brain", TCD is a state–of–the–art imaging test that is non–invasive, painless, and safe.

Testing Services

Transcranial Doppler
Transcranial Doppler uses sophisticated ultrasound technology to accurately detect and assess narrowing of the cranial blood vessels (stenosis) and micro–embolization in the bloodstream. Detection of these findings helps neurologists, neurosurgeons, cardiologists, cardiovascular surgeons and general practitioners in their diagnosis of patients; determining treatments; and improving treatment outcomes. TCD complements carotid duplex testing by providing information about intracranial portion of the carotid artery; and end–organ flow patterns associated with collaterals in the brain arteries.

Transcranial Color Coded Duplex
Transcranial color-coded duplex (TCCD) is an enhanced TCD technique for measuring cerebral artery stenosis (narrowing) by visualizing blood vessels and surrounding tissues. TCCD adds B-mode imaging and color coding of the Doppler signal to transcranial Doppler sonography (TCD); enabling enhanced identification of the insonated artery and the direction of blood flow. This test is a very useful alternative to more invasive procedures for evaluating stroke.

Carotid Duplex
Carotid artery disease is a common, treatable narrowing of arteries in the neck that may lead to stroke. Carotid duplex testing is another simple and non–invasive ultrasound test able to measure the degree of narrowing in the carotid arteries; combined with ultrasound Doppler to measure blood flow. This test may be repeated over time to measure the progression of carotid stenosis; enabling physicians to determine if and when an intervention is required.

Diagnostic Test Results
The Transcranial Imaging Center is capable of producing the following diagnostic results:

  • Indication of blood flow status, quantitatively assessing cerebral hemodynamics and measuring linear cerebral blood flow velocities (CBFV) in cm/s.
  • Identification of significant abnormalities and lesions, like stenosis/narrowing of the brain vasculature or decreased blood flow.
  • Evaluation and help in diagnosing stroke etiology, TIA, vertebrobasilar insufficiency, and symptomatic/asymptomatic carotid artery lesions.
  • TCD Bubble test with agitated saline (for right–to–left shunt, PFO or ASD, PFO with Headaches).
  • TCD with head turning maneuver to rule out vertebral artery compression.
  • Assessment of embolization in the cerebral circulation and detection of emboli in vivo (in real–time for patients with irregular heart rate, prosthetic valve, LVAD). TCD is the only tool for embolus detection.
  • Monitoring of emboli during major cardiovascular surgery such as carotid endarterectomy, carotid stenting, cardiac valve replacement, and aortic aneurysm repair.
  • Measurement of vasomotor reactivity using Breath Holding Index for carotid stenosis, MCA, or VA stenosis.

Patient Information

What is Transcranial Doppler?
A transcranial Doppler (TCD) test is a safe, non–invasive ultrasound test ordered by your physician to measure blood circulation in and around the brain. Testing simply involves placing a small transducer on the skin’s surface, usually on the eyelid, in front of the ears, or on the back of the neck in order to record blood flow information. There is virtually no discomfort during the test which typically lasts no more than 30 minutes. Ultrasound does not use radiation and there are no harmful side effects.

The Testing Process

  • No special preparation is required for a TCD test. Please no make up and wait until your test is done to visit your hairdresser.
  • You are not required to change into a hospital gown or remove jewelry; and please turn your cell phone off.
  • The test is performed by specially–trained technologists or a physician.
  • You may be asked to lay down or sit in a chair during the test.
  • Water–soluble gel is applied to the skin over the area to be examined.
  • You will be asked to remain still during the test.
  • The test results will be forwarded to your physician who will discuss the results with you.

How to Order Testing

Physicians should contact the Transcranial Imaging Center at 713–441–5200 for a testing order form. This one page form requires basic patient information and history (please provide any previous imaging reports if available); and offers a checklist of available services. Completed order forms should be faxed to 713–441–6298. To request a stat test, page 713–768–0542.

Training Programs

The Transcranial Imaging Center has a continued commitment to education in cerebrovascular ultrasound techniques. Individualized training courses in transcranial Doppler, transcranial duplex imaging, and carotid duplex studies are offered in either a 5–day (weekday) or a 2–day (weekend) format. The courses are directed toward physicians involved in caring for patients with stroke (neurologists, neurosurgeons, vascular surgeons, and neurointensivists); and vascular technologists and other health professionals who need training in vascular ultrasound technology. Contact the Transcranial Imaging Center at 713–441–5200 for more information and upcoming course dates. The current training schedule may be downloaded.


The Director of the Transcranial Imaging Center is Dr. Zsolt Garami, a nationally–recognized leader in TCD. Dr. Garami’s research focuses on understanding and treating intracranial flow disturbances that cause stroke. He has numerous publications on the monitoring of the cerebral vasculature during vascular procedures such as coronary artery bypass grafting, and carotid artery surgery. His current studies aim to reveal critical patterns of distal intracranial embolization in LVAD patients. For more information on Dr. Garami’s background, research interests, current studies, and publications, please visit his web page at The Methodist Hospital Research Institute. Dr. Garami may be contacted at: zgarami@houstonmethodist.org.