In transorbital Doppler, which vessel at 40-60 mm depth with antegrade flow around 21 cm/s is described?

• A. Internal carotid artery
• B. Anterior cerebral artery
• C. Ophthalmic artery
• D. Middle cerebral artery

Answer: (A)

Transorbital Doppler uses the orbit as an acoustic window to image intracranial arteries, so the depth at which you detect a vessel helps identify it. A vessel seen at about 40–60 mm with an antegrade waveform and a velocity near 21 cm/s best fits the intracranial portion of the internal carotid artery as it courses medially toward the circle of Willis. The ophthalmic artery can also be seen through this window, but its Doppler pattern and typical depth often differ, and the anterior cerebral and middle cerebral arteries are generally assessed with other windows or angles. Thus, the described vessel corresponds to the internal carotid artery.