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For more than 25 years, Transcranial Doppler (TCD) examinations have been performed. Although TCD is commonly a neurology/neurosurgery specialty testing procedure, there are areas of interest for both cardiology and vascular medicine/surgery as well. TCD is performed with a 1.5 – 2.5 MHz pulsed wave bidirectional range-gated Doppler transducer. TCI (transcranial imaging), also known as color coded Doppler imaging, is performed with a duplex ultrasound machine using B-mode imaging technique and color flow Doppler to guide the sonographer in proper cursor placement, alignment and the ability for angle correction.

TCD, although time consuming to the less experienced, is a valuable exam. The exam can be modified and performed quickly in emergency situations at the patient bedside, repeated as often as medically necessary or used for continuous monitoring. The TCD examination is cost effective and is noninvasive as compared to other imaging procedures such as MRA and CTA.

Getting Started

The main parameters for identifying the cerebral arteries are insonation depth, flow velocities, the direction of blood flow at that depth, both peak systolic and diastolic flow velocities, the site of the probe position, the angle or direction of the ultrasound beam, and the traceability of the vessels. The response to the common carotid artery vibration or compression can also be used for vessel identification.

Optimally, the patient should be supine for the anterior circulation exam. To obtain the posterior circulation exam, the patient can simply lie with the head turned to the side, sit up in a chair with the chin resting on the chest or lie in a lateral decubitus position.

A complete TCD exam that meets all of the ICAVL Standards includes, but is not limited to, the following:

• TCD exams must be bilateral for the anterior circulation vessels and include assessment of the intracranial posterior circulation vessels including both vertebral and the basilar arteries.


• Specific spectral Doppler images must be documented from up to four cranial windows to ensure the interrogation of flow in the anterior and posterior circulation.


• Flow velocities and direction of flow must be documented at the following vessel sites:
  • Intracranial internal carotid arteries
  • A1 segment of the anterior cerebral arteries
  • M1-proximal M2 Middle cerebral arteries
  • P1 or P2 Posterior cerebral arteries
  • Ophthalmic artery
  • Internal carotid artery siphon
  • Distal internal carotid artery on the neck (when appropriate)
  • Distal vertebral arteries
  • Proximal and distal basilar artery

On rare occasion, common carotid artery or vertebral artery vibration or compression maneuvers may be required to unequivocally identify certain vessels or collateral pathways. This exam should only be performed either by a physician or an experienced sonographer with phycisian supervision. In this situation, the investigator must evaluate the status of extracranial carotid artery stenosis before the compression maneuvers. Hemodynamically significant extracranial internal or common carotid artery disease can lead to erroneous intracranial artery diagnosis.

What are the most common TCD/TCI indications?

TCD/TCI is indicated for diagnostic work-up, monitoring and follow-up for patients with ischemic strokes and transient ischemic attacks. Examples of TCD/TCI tests:

• Complete TCD examination
• Limited TCD examination
• Emboli detection with contrast injection (detection of a right-to-left shunt)
• Emboli detection without contrast injection
• Vasomotor reactivity assessment

TCD is indicated to detect, grade and localize steno-occlusive lesions, collateral channels and brain embolization, including spontaneous or via the paradoxical embolism pathway (such as patent foramen ovale).

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