Extracranial
This is the approximate percentage of blood flow to the brain that is supplied by the bilateral internal carotid arteries.
What is 80%?
The extracranial portion of these vessels arise from the subclavian arteries, run through the cervical vertebra and come together intracranially to form the basilar artery.
What are the vertebral arteries?
This is the eponymous name of arterial ring at the base of the brain.
What is the circle of Willis?
This happens when there is a high-to-low energy gradient.
What is flow?
This is what we call a mechanical wave of rhythmic oscillation of pressure.
What is sound?
This "great vessel" gives rise to the innominate, subclavian, and the common carotid arteries.
What is the aorta?
This vessel is formed by the confluence of the vertebral arteries.
What is the basilar artery?
This communicating aspect of the Circle of Willis provides a connection between the anterior and posterior circulations.
What is the Posterior Communicating Artery? (Pcomm)
This is the type of flow where streamlines are aligned and parallel layers traveling at an individual speed (physiologic flow).
What is laminar flow?
These are the Doppler angles that get you "true" velocity.
What is 0 or 180?
This major vessel branches into the Internal and External Carotid arteries.
What is the Common Carotid artery?
This vessel originates from the terminus of the internal carotid artery and heads laterally, toward the ear.
What is the Middle Cerebral Artery?
This is the segment that connects the right and left halves of the anterior circulation, and is a "first line" collateral pathway.
What is the Anterior Communicating artery?
One of three reasons blood loses energy as it flows, this term refers to the "stickiness" of blood, driven by hematocrit, that must be overcome for forward flow.
What is viscosity?
This characteristic of sound describes the number of cycles per unit of time, usually expressed in Hertz.
What is frequency?
This branch of the common carotid artery gives rise to multiple branches outside of the skull.
What is the external carotid artery?
This intracranial vessel supplies blood to the occipital lobe in "the back of the brain."
What is the Posterior Cerebral artery?
This is the most proximal branch of the intracranial Internal Carotid artery that can be insonated by TCD.
What is the Ophthalmic Artery?
This is the principle that explains why velocity increases near a focal stenosis.
What is the Continuity of Energy? (will accept Continuity of volume flow rate)
This is the type of attenuation that is the basis of diagnostic ultrasound.
What is Reflection?
This is the nickname of the "S" curve the internal carotid artery (ICA) takes as it enters the skull.
What is the Siphon?
This window of insonation through the skull provides access to the most vessel segments.
What is the transtemporal window?
These are the intracranial arteries being referred to when we speak of "the bifurcation," typically located at around 65-70mm of depth from a transtemporal window.
What are the Middle Cerebral and Anterior Cerebral arteries?
This is the part of the Spencer curve in which we see normal or low velocity in the setting of very severe stenosis.
What is the "Left half" of the Spencer curve?
This is the term for the highest Doppler shift that can be accurately measured without aliasing.
What is the Nyquist Limit?