Intracranial Cerebrovascular Doppler TEST Flashcards
What is TCD (transcranial doppler) based on?
hemodynamics (how is the blood flowing)
What are they trying to evaluate in intracranial doppler?
The blood vessels in the Circle of Wilis
Why was TCD initially developed?
to detect vasospasm following a subarachnoid hemorrhage
Is TCD invasive?
non invasive
portable
painless
safe
inexpensive
REPEATABLE
What does TCD do?
measures velocity
Identifies direction of flow
What are the limitations of TCD?
operator dependent - steady hand
blind vessel identification
anatomic variants
skull difficult to penetrate
Why do we do TCD?
occlusive Disease
cerebral emboli
hemorrhage
sickle cell disease
subclavian steal
head trauma
cerebrovascular disease
stroke
migraine headaches
aneurysms
AV fistula
vasospasm
evaluation of brain death
eval of collateral flow
What are the two routes that blood is delivered to the brain?
internal carotids and vertebrals that form an anterior circulation and a posterior circulation respectively
What is the circle of Willis?
ring that permits communication between the rt and lt cerebral hemispheres
and between anterior and posterior systems
What does the circle of willis consist of?
A1 segments of the
two ACA’s
ACoA
two PCoA’s
two ICA’s
P1 segment of the two PCA’s
What does the circle of willis actually do?
polygon shaped vascular ring
at the base of the brain
communication between rt and lt cerebral hemisphere
communication between ant and post systems
What vessels are in the anterior circulation?
ICA
MCA (middle cerebral artery)
ACA (anterior cerebral artery)
ACoA
What is the first branch off of the ICA?
Opthalmic artery
Can the Opthalmic artery be scanned?
yes by TCD
Why is the Opthalmic artery important?
Role in collateral pathways
What is the carotid siphon?
portion of the ICA that forms two curves
The ICA bifurcates into two terminal branches…what are they?
anterior cerebral artery
middle cerebral artery
very curved branches
The anterior circulation is via the ___________ ___________ artery
anterior communicating artery ACOM
Posterior circulation via the _____________ ____________ artery
Posterior communicating artery PCOM
What is COW?
circle of willis
Which artery cannot be visualized by TCD?
anterior communicating artery ACoA
What do you use to perform TCD?
phased array
Pulsed doppler
CW can be used
2-5 MHz (for penetration)
0 degree angle
capture the entire circle of willis
The real time display of all doppler shift frequencies over ______ is the doppler _________ waveform
time
spectral
A ___________doppler shift is ___________the baseline
positive
above
a __________doppler shift is _________the baseline
negative
below
During TCD imaging the doppler _________ should be _______ for adequate penetration
Power
Increased
What is key information for TCD?
depth
the flow toward and away is most important which color is which
Blue - away
Red- toward
What are the four TCD windows?
transtemporal (above the ear)
transorbital (eye)
transoccipital, suboccipital
submandibular (under the chin)
FRom the transtemporal window, what vessels can you see?
MCA
ACA
MCA/ACA (bifurcation - butterfly sign)
PCA
ICA
MCA courses adjacent to the ____________ _________
sphenoid wing
PCA wraps around the ____________ ____________
cerebral peduncle
Decrease ________for slower flow in the PCA and ACA
PRF (scale)
Opthalmic artery is __________resistance
high
Transtemporal arteries are _______resistance
low
What do you do with the power for transorbital?
decrease the power
ALARA - as low as reasonably acheivable.
What artery gets reversed flow with stenosis in the ICA?
ophthalmic artery
The trans/suboccipital window places the transducer….
on the posterior aspect of the neck inferior to the nuchal crest
What do you see in the suboccipital area?
vertebral
basilar
distal ICA
Y sign
see slide 49 for picture
How do you get good quality color doppler images?
increase color gain
small sector width and color box for highest possible frame rates
change color PRF
color sensitivity and persistence settings (makes the color come out more than gray scale)
What kind of flow are you looking for in TCD?
mean flow velocity - not peak
Why is the color display important?
assists in the proper placement of sample
know slides….
54 -55
look in Ipad pictures
describe stenosis
increased velocities
turbulence
describe occusion
no flow
insonating (sweeping) the vessel is key
What are the doppler findings for Stenosis? occlusion? vasospasm? sickle cell anemia?
stenosis: increased velocities - turbulence
occlusion: no flow - insonating vessel key
vasospasm: increased velocities - sequential doppler
sickle cell: increased velocities in the ICA MCA
describe AV malformations and doppler
increase velocities
low pulsatility
turbulance
how does age affect velocities?
lower with increasing age
how does being female affect velocities?
slight increase
What are the physiologic factors for non disease related intracranial changes in doppler?
age: lower velocities with ^ age
sex: slight ^ velocities with females
Hematocrit: velocities ^ with anemia
heart rate/cardiac output
What is a stenosis?
focal ^ in velocity
local turbulence
poststenotic dtop
PRF ^
antegrade means? retrograde means?
antegrade - up
retrograde - down
What is vasospasm?
vasoconstriction of the arteries
complication of hemorrhage
^ velocity
What can cause hemorrahge?
ruptured aneurysm
vascular tumor
head trauma
If there is an aneurysm, what two things might you see with color doppler?
color flow appearing in an unexpected area
wider color area
What is a subclavian steal?
associated with stenosis or occlusion of subclavian artery
vertebral becomes collateral
When you have a subclavian steal, which artery get “stolen” from?
basilar
What happens to the vertebral artery with a subclavian steal?
retrograde flow
causes patient to experience neurologic symptoms of brain stem ischemia
If you have an innominate or subclavian artery obstruction, what is the difference in systolic pressure between arms?
> 20 mmHg
obstruction on the side of lower pressure
If you have an emboli what will you hear/see?
high intensity signal
hear a chirp
see a spike
What do you do to detect an emboli?
Use main MCA
transient signal
higher amplitude
unidirectional
audio sound - snap
What is sickle cell disease?
inherited blood disorder
cerebral infarction associated with occlusion
