Extracranial
What percentage of blood flow to the brain is supplied by the ICAs.
Approximately 75%
These vessels arise from the subclavian arteries and provide blood flow to the posterior circulation.
The vertebral arteries
The circle of Willis
Why does flow happen?
Flow happens because of energy gradients, high to low.
What makes a wave "sound?"
rhythmic oscillation of pressure, density or distance
This heart component gives rise to the subclavian arteries and the common carotid arteries.
The aortic arch
This vessel is formed by the confluence of the vertebral arteries.
The basilar artery
This communicating artery provides blood flow between the anterior and posterior circulations of the brain .
The PCOM
Type of flow where streamlines are aligned and parallel layers traveling at an individual speed (physiologic flow).
Laminar
Which Doppler angle gets you "true" velocity?
0 or 180
What is the main branch of the carotid artery.
The CCA
This vessel is larger than the ACA an originates from the bifurcation of the ICA.
The MCA
This artery is a short vessel that connects the A1 ACA segments to allow for collateral formation.
The ACOM
What are three reasons blood loses energy as it flows?
viscosity – overcoming “stickiness,” driven by hematocrit
friction – blood “rubbing” against endothelium generating heat or mechanical energy
inertia – tendency to resist changes in velocity
Name any 3 characteristics of sound
period – time for 1 cycle (time)
frequency – number of cycles/time (Hz)
amplitude – Δmax/min and average (pressure, density or distance)
power – energy transfer, “work” (watts)
intensity – area in which power is distributed (watt/beam area)
wavelength – length of 1 cycle (length)
propagation speed – rate of travel through a medium (distance/time)
What vessel of the carotid artery gives rise to multiple branches?
The ECA
This intracranial vessel is divided into multiple segments
The MCA
4
Why does velocity increase in a stenosis?
continuity of volume flow rate
Which type of attenuation is the basis of diagnostic ultrasound?
Reflection
The ICA Siphon
What arteries arise from the terminal ICA?
MCA and ACA
This artery is the 1st branch of the ICA in the cerebral segment
The OA
Why might we see normal or low velocity in the setting of very severe stenosis?
"Left half" of Spencer curve
What is the term for the highest Doppler shift that can be accurately measured? (bonus 300pt for how it's calculated!)
Nyquist Limit
(PRF/2)